(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('react')) :
  typeof define === 'function' && define.amd ? define(['exports', 'react'], factory) :
  (global = global || self, factory(global.ReactDnD = {}, global.React));
}(this, (function (exports, React) { 'use strict';

  var HandlerRole;

  (function (HandlerRole) {
    HandlerRole["SOURCE"] = "SOURCE";
    HandlerRole["TARGET"] = "TARGET";
  })(HandlerRole || (HandlerRole = {}));

  function symbolObservablePonyfill(root) {
  	var result;
  	var Symbol = root.Symbol;

  	if (typeof Symbol === 'function') {
  		if (Symbol.observable) {
  			result = Symbol.observable;
  		} else {
  			result = Symbol('observable');
  			Symbol.observable = result;
  		}
  	} else {
  		result = '@@observable';
  	}

  	return result;
  }

  /* global window */

  var root;

  if (typeof self !== 'undefined') {
    root = self;
  } else if (typeof window !== 'undefined') {
    root = window;
  } else if (typeof global !== 'undefined') {
    root = global;
  } else if (typeof module !== 'undefined') {
    root = module;
  } else {
    root = Function('return this')();
  }

  var result = symbolObservablePonyfill(root);

  /**
   * These are private action types reserved by Redux.
   * For any unknown actions, you must return the current state.
   * If the current state is undefined, you must return the initial state.
   * Do not reference these action types directly in your code.
   */
  var randomString = function randomString() {
    return Math.random().toString(36).substring(7).split('').join('.');
  };

  var ActionTypes = {
    INIT: "@@redux/INIT" + randomString(),
    REPLACE: "@@redux/REPLACE" + randomString(),
    PROBE_UNKNOWN_ACTION: function PROBE_UNKNOWN_ACTION() {
      return "@@redux/PROBE_UNKNOWN_ACTION" + randomString();
    }
  };

  /**
   * @param {any} obj The object to inspect.
   * @returns {boolean} True if the argument appears to be a plain object.
   */
  function isPlainObject(obj) {
    if (typeof obj !== 'object' || obj === null) return false;
    var proto = obj;

    while (Object.getPrototypeOf(proto) !== null) {
      proto = Object.getPrototypeOf(proto);
    }

    return Object.getPrototypeOf(obj) === proto;
  }

  /**
   * Creates a Redux store that holds the state tree.
   * The only way to change the data in the store is to call `dispatch()` on it.
   *
   * There should only be a single store in your app. To specify how different
   * parts of the state tree respond to actions, you may combine several reducers
   * into a single reducer function by using `combineReducers`.
   *
   * @param {Function} reducer A function that returns the next state tree, given
   * the current state tree and the action to handle.
   *
   * @param {any} [preloadedState] The initial state. You may optionally specify it
   * to hydrate the state from the server in universal apps, or to restore a
   * previously serialized user session.
   * If you use `combineReducers` to produce the root reducer function, this must be
   * an object with the same shape as `combineReducers` keys.
   *
   * @param {Function} [enhancer] The store enhancer. You may optionally specify it
   * to enhance the store with third-party capabilities such as middleware,
   * time travel, persistence, etc. The only store enhancer that ships with Redux
   * is `applyMiddleware()`.
   *
   * @returns {Store} A Redux store that lets you read the state, dispatch actions
   * and subscribe to changes.
   */

  function createStore(reducer, preloadedState, enhancer) {
    var _ref2;

    if (typeof preloadedState === 'function' && typeof enhancer === 'function' || typeof enhancer === 'function' && typeof arguments[3] === 'function') {
      throw new Error('It looks like you are passing several store enhancers to ' + 'createStore(). This is not supported. Instead, compose them ' + 'together to a single function.');
    }

    if (typeof preloadedState === 'function' && typeof enhancer === 'undefined') {
      enhancer = preloadedState;
      preloadedState = undefined;
    }

    if (typeof enhancer !== 'undefined') {
      if (typeof enhancer !== 'function') {
        throw new Error('Expected the enhancer to be a function.');
      }

      return enhancer(createStore)(reducer, preloadedState);
    }

    if (typeof reducer !== 'function') {
      throw new Error('Expected the reducer to be a function.');
    }

    var currentReducer = reducer;
    var currentState = preloadedState;
    var currentListeners = [];
    var nextListeners = currentListeners;
    var isDispatching = false;
    /**
     * This makes a shallow copy of currentListeners so we can use
     * nextListeners as a temporary list while dispatching.
     *
     * This prevents any bugs around consumers calling
     * subscribe/unsubscribe in the middle of a dispatch.
     */

    function ensureCanMutateNextListeners() {
      if (nextListeners === currentListeners) {
        nextListeners = currentListeners.slice();
      }
    }
    /**
     * Reads the state tree managed by the store.
     *
     * @returns {any} The current state tree of your application.
     */


    function getState() {
      if (isDispatching) {
        throw new Error('You may not call store.getState() while the reducer is executing. ' + 'The reducer has already received the state as an argument. ' + 'Pass it down from the top reducer instead of reading it from the store.');
      }

      return currentState;
    }
    /**
     * Adds a change listener. It will be called any time an action is dispatched,
     * and some part of the state tree may potentially have changed. You may then
     * call `getState()` to read the current state tree inside the callback.
     *
     * You may call `dispatch()` from a change listener, with the following
     * caveats:
     *
     * 1. The subscriptions are snapshotted just before every `dispatch()` call.
     * If you subscribe or unsubscribe while the listeners are being invoked, this
     * will not have any effect on the `dispatch()` that is currently in progress.
     * However, the next `dispatch()` call, whether nested or not, will use a more
     * recent snapshot of the subscription list.
     *
     * 2. The listener should not expect to see all state changes, as the state
     * might have been updated multiple times during a nested `dispatch()` before
     * the listener is called. It is, however, guaranteed that all subscribers
     * registered before the `dispatch()` started will be called with the latest
     * state by the time it exits.
     *
     * @param {Function} listener A callback to be invoked on every dispatch.
     * @returns {Function} A function to remove this change listener.
     */


    function subscribe(listener) {
      if (typeof listener !== 'function') {
        throw new Error('Expected the listener to be a function.');
      }

      if (isDispatching) {
        throw new Error('You may not call store.subscribe() while the reducer is executing. ' + 'If you would like to be notified after the store has been updated, subscribe from a ' + 'component and invoke store.getState() in the callback to access the latest state. ' + 'See https://redux.js.org/api-reference/store#subscribe(listener) for more details.');
      }

      var isSubscribed = true;
      ensureCanMutateNextListeners();
      nextListeners.push(listener);
      return function unsubscribe() {
        if (!isSubscribed) {
          return;
        }

        if (isDispatching) {
          throw new Error('You may not unsubscribe from a store listener while the reducer is executing. ' + 'See https://redux.js.org/api-reference/store#subscribe(listener) for more details.');
        }

        isSubscribed = false;
        ensureCanMutateNextListeners();
        var index = nextListeners.indexOf(listener);
        nextListeners.splice(index, 1);
      };
    }
    /**
     * Dispatches an action. It is the only way to trigger a state change.
     *
     * The `reducer` function, used to create the store, will be called with the
     * current state tree and the given `action`. Its return value will
     * be considered the **next** state of the tree, and the change listeners
     * will be notified.
     *
     * The base implementation only supports plain object actions. If you want to
     * dispatch a Promise, an Observable, a thunk, or something else, you need to
     * wrap your store creating function into the corresponding middleware. For
     * example, see the documentation for the `redux-thunk` package. Even the
     * middleware will eventually dispatch plain object actions using this method.
     *
     * @param {Object} action A plain object representing “what changed”. It is
     * a good idea to keep actions serializable so you can record and replay user
     * sessions, or use the time travelling `redux-devtools`. An action must have
     * a `type` property which may not be `undefined`. It is a good idea to use
     * string constants for action types.
     *
     * @returns {Object} For convenience, the same action object you dispatched.
     *
     * Note that, if you use a custom middleware, it may wrap `dispatch()` to
     * return something else (for example, a Promise you can await).
     */


    function dispatch(action) {
      if (!isPlainObject(action)) {
        throw new Error('Actions must be plain objects. ' + 'Use custom middleware for async actions.');
      }

      if (typeof action.type === 'undefined') {
        throw new Error('Actions may not have an undefined "type" property. ' + 'Have you misspelled a constant?');
      }

      if (isDispatching) {
        throw new Error('Reducers may not dispatch actions.');
      }

      try {
        isDispatching = true;
        currentState = currentReducer(currentState, action);
      } finally {
        isDispatching = false;
      }

      var listeners = currentListeners = nextListeners;

      for (var i = 0; i < listeners.length; i++) {
        var listener = listeners[i];
        listener();
      }

      return action;
    }
    /**
     * Replaces the reducer currently used by the store to calculate the state.
     *
     * You might need this if your app implements code splitting and you want to
     * load some of the reducers dynamically. You might also need this if you
     * implement a hot reloading mechanism for Redux.
     *
     * @param {Function} nextReducer The reducer for the store to use instead.
     * @returns {void}
     */


    function replaceReducer(nextReducer) {
      if (typeof nextReducer !== 'function') {
        throw new Error('Expected the nextReducer to be a function.');
      }

      currentReducer = nextReducer; // This action has a similiar effect to ActionTypes.INIT.
      // Any reducers that existed in both the new and old rootReducer
      // will receive the previous state. This effectively populates
      // the new state tree with any relevant data from the old one.

      dispatch({
        type: ActionTypes.REPLACE
      });
    }
    /**
     * Interoperability point for observable/reactive libraries.
     * @returns {observable} A minimal observable of state changes.
     * For more information, see the observable proposal:
     * https://github.com/tc39/proposal-observable
     */


    function observable() {
      var _ref;

      var outerSubscribe = subscribe;
      return _ref = {
        /**
         * The minimal observable subscription method.
         * @param {Object} observer Any object that can be used as an observer.
         * The observer object should have a `next` method.
         * @returns {subscription} An object with an `unsubscribe` method that can
         * be used to unsubscribe the observable from the store, and prevent further
         * emission of values from the observable.
         */
        subscribe: function subscribe(observer) {
          if (typeof observer !== 'object' || observer === null) {
            throw new TypeError('Expected the observer to be an object.');
          }

          function observeState() {
            if (observer.next) {
              observer.next(getState());
            }
          }

          observeState();
          var unsubscribe = outerSubscribe(observeState);
          return {
            unsubscribe: unsubscribe
          };
        }
      }, _ref[result] = function () {
        return this;
      }, _ref;
    } // When a store is created, an "INIT" action is dispatched so that every
    // reducer returns their initial state. This effectively populates
    // the initial state tree.


    dispatch({
      type: ActionTypes.INIT
    });
    return _ref2 = {
      dispatch: dispatch,
      subscribe: subscribe,
      getState: getState,
      replaceReducer: replaceReducer
    }, _ref2[result] = observable, _ref2;
  }

  /**
   * Prints a warning in the console if it exists.
   *
   * @param {String} message The warning message.
   * @returns {void}
   */
  function warning(message) {
    /* eslint-disable no-console */
    if (typeof console !== 'undefined' && typeof console.error === 'function') {
      console.error(message);
    }
    /* eslint-enable no-console */


    try {
      // This error was thrown as a convenience so that if you enable
      // "break on all exceptions" in your console,
      // it would pause the execution at this line.
      throw new Error(message);
    } catch (e) {} // eslint-disable-line no-empty

  }

  /*
   * This is a dummy function to check if the function name has been altered by minification.
   * If the function has been minified and NODE_ENV !== 'production', warn the user.
   */

  function isCrushed() {}

  if ("development" !== 'production' && typeof isCrushed.name === 'string' && isCrushed.name !== 'isCrushed') {
    warning('You are currently using minified code outside of NODE_ENV === "production". ' + 'This means that you are running a slower development build of Redux. ' + 'You can use loose-envify (https://github.com/zertosh/loose-envify) for browserify ' + 'or setting mode to production in webpack (https://webpack.js.org/concepts/mode/) ' + 'to ensure you have the correct code for your production build.');
  }

  /**
   * Use invariant() to assert state which your program assumes to be true.
   *
   * Provide sprintf-style format (only %s is supported) and arguments
   * to provide information about what broke and what you were
   * expecting.
   *
   * The invariant message will be stripped in production, but the invariant
   * will remain to ensure logic does not differ in production.
   */
  function invariant(condition, format) {
    for (var _len = arguments.length, args = new Array(_len > 2 ? _len - 2 : 0), _key = 2; _key < _len; _key++) {
      args[_key - 2] = arguments[_key];
    }

    if ("development" !== 'production') {
      if (format === undefined) {
        throw new Error('invariant requires an error message argument');
      }
    }

    if (!condition) {
      var error;

      if (format === undefined) {
        error = new Error('Minified exception occurred; use the non-minified dev environment ' + 'for the full error message and additional helpful warnings.');
      } else {
        var argIndex = 0;
        error = new Error(format.replace(/%s/g, function () {
          return args[argIndex++];
        }));
        error.name = 'Invariant Violation';
      }

      error.framesToPop = 1; // we don't care about invariant's own frame

      throw error;
    }
  }

  var INIT_COORDS = 'dnd-core/INIT_COORDS';
  var BEGIN_DRAG = 'dnd-core/BEGIN_DRAG';
  var PUBLISH_DRAG_SOURCE = 'dnd-core/PUBLISH_DRAG_SOURCE';
  var HOVER = 'dnd-core/HOVER';
  var DROP = 'dnd-core/DROP';
  var END_DRAG = 'dnd-core/END_DRAG';

  function setClientOffset(clientOffset, sourceClientOffset) {
    return {
      type: INIT_COORDS,
      payload: {
        sourceClientOffset: sourceClientOffset || null,
        clientOffset: clientOffset || null
      }
    };
  }

  function _typeof(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof(obj); }

  // cheap lodash replacements

  /**
   * drop-in replacement for _.get
   * @param obj
   * @param path
   * @param defaultValue
   */
  function get(obj, path, defaultValue) {
    return path.split('.').reduce(function (a, c) {
      return a && a[c] ? a[c] : defaultValue || null;
    }, obj);
  }
  /**
   * drop-in replacement for _.without
   */

  function without(items, item) {
    return items.filter(function (i) {
      return i !== item;
    });
  }
  /**
   * drop-in replacement for _.isString
   * @param input
   */

  function isObject(input) {
    return _typeof(input) === 'object';
  }
  /**
   * repalcement for _.xor
   * @param itemsA
   * @param itemsB
   */

  function xor(itemsA, itemsB) {
    var map = new Map();

    var insertItem = function insertItem(item) {
      return map.set(item, map.has(item) ? map.get(item) + 1 : 1);
    };

    itemsA.forEach(insertItem);
    itemsB.forEach(insertItem);
    var result = [];
    map.forEach(function (count, key) {
      if (count === 1) {
        result.push(key);
      }
    });
    return result;
  }
  /**
   * replacement for _.intersection
   * @param itemsA
   * @param itemsB
   */

  function intersection(itemsA, itemsB) {
    return itemsA.filter(function (t) {
      return itemsB.indexOf(t) > -1;
    });
  }

  var ResetCoordinatesAction = {
    type: INIT_COORDS,
    payload: {
      clientOffset: null,
      sourceClientOffset: null
    }
  };
  function createBeginDrag(manager) {
    return function beginDrag() {
      var sourceIds = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : [];
      var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
        publishSource: true
      };
      var _options$publishSourc = options.publishSource,
          publishSource = _options$publishSourc === void 0 ? true : _options$publishSourc,
          clientOffset = options.clientOffset,
          getSourceClientOffset = options.getSourceClientOffset;
      var monitor = manager.getMonitor();
      var registry = manager.getRegistry(); // Initialize the coordinates using the client offset

      manager.dispatch(setClientOffset(clientOffset));
      verifyInvariants(sourceIds, monitor, registry); // Get the draggable source

      var sourceId = getDraggableSource(sourceIds, monitor);

      if (sourceId === null) {
        manager.dispatch(ResetCoordinatesAction);
        return;
      } // Get the source client offset


      var sourceClientOffset = null;

      if (clientOffset) {
        verifyGetSourceClientOffsetIsFunction(getSourceClientOffset);
        sourceClientOffset = getSourceClientOffset(sourceId);
      } // Initialize the full coordinates


      manager.dispatch(setClientOffset(clientOffset, sourceClientOffset));
      var source = registry.getSource(sourceId);
      var item = source.beginDrag(monitor, sourceId);
      verifyItemIsObject(item);
      registry.pinSource(sourceId);
      var itemType = registry.getSourceType(sourceId);
      return {
        type: BEGIN_DRAG,
        payload: {
          itemType: itemType,
          item: item,
          sourceId: sourceId,
          clientOffset: clientOffset || null,
          sourceClientOffset: sourceClientOffset || null,
          isSourcePublic: !!publishSource
        }
      };
    };
  }

  function verifyInvariants(sourceIds, monitor, registry) {
    invariant(!monitor.isDragging(), 'Cannot call beginDrag while dragging.');
    sourceIds.forEach(function (sourceId) {
      invariant(registry.getSource(sourceId), 'Expected sourceIds to be registered.');
    });
  }

  function verifyGetSourceClientOffsetIsFunction(getSourceClientOffset) {
    invariant(typeof getSourceClientOffset === 'function', 'When clientOffset is provided, getSourceClientOffset must be a function.');
  }

  function verifyItemIsObject(item) {
    invariant(isObject(item), 'Item must be an object.');
  }

  function getDraggableSource(sourceIds, monitor) {
    var sourceId = null;

    for (var i = sourceIds.length - 1; i >= 0; i--) {
      if (monitor.canDragSource(sourceIds[i])) {
        sourceId = sourceIds[i];
        break;
      }
    }

    return sourceId;
  }

  function createPublishDragSource(manager) {
    return function publishDragSource() {
      var monitor = manager.getMonitor();

      if (monitor.isDragging()) {
        return {
          type: PUBLISH_DRAG_SOURCE
        };
      }
    };
  }

  function matchesType(targetType, draggedItemType) {
    if (draggedItemType === null) {
      return targetType === null;
    }

    return Array.isArray(targetType) ? targetType.some(function (t) {
      return t === draggedItemType;
    }) : targetType === draggedItemType;
  }

  function createHover(manager) {
    return function hover(targetIdsArg) {
      var _ref = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {},
          clientOffset = _ref.clientOffset;

      verifyTargetIdsIsArray(targetIdsArg);
      var targetIds = targetIdsArg.slice(0);
      var monitor = manager.getMonitor();
      var registry = manager.getRegistry();
      checkInvariants(targetIds, monitor, registry);
      var draggedItemType = monitor.getItemType();
      removeNonMatchingTargetIds(targetIds, registry, draggedItemType);
      hoverAllTargets(targetIds, monitor, registry);
      return {
        type: HOVER,
        payload: {
          targetIds: targetIds,
          clientOffset: clientOffset || null
        }
      };
    };
  }

  function verifyTargetIdsIsArray(targetIdsArg) {
    invariant(Array.isArray(targetIdsArg), 'Expected targetIds to be an array.');
  }

  function checkInvariants(targetIds, monitor, registry) {
    invariant(monitor.isDragging(), 'Cannot call hover while not dragging.');
    invariant(!monitor.didDrop(), 'Cannot call hover after drop.');

    for (var i = 0; i < targetIds.length; i++) {
      var targetId = targetIds[i];
      invariant(targetIds.lastIndexOf(targetId) === i, 'Expected targetIds to be unique in the passed array.');
      var target = registry.getTarget(targetId);
      invariant(target, 'Expected targetIds to be registered.');
    }
  }

  function removeNonMatchingTargetIds(targetIds, registry, draggedItemType) {
    // Remove those targetIds that don't match the targetType.  This
    // fixes shallow isOver which would only be non-shallow because of
    // non-matching targets.
    for (var i = targetIds.length - 1; i >= 0; i--) {
      var targetId = targetIds[i];
      var targetType = registry.getTargetType(targetId);

      if (!matchesType(targetType, draggedItemType)) {
        targetIds.splice(i, 1);
      }
    }
  }

  function hoverAllTargets(targetIds, monitor, registry) {
    // Finally call hover on all matching targets.
    targetIds.forEach(function (targetId) {
      var target = registry.getTarget(targetId);
      target.hover(monitor, targetId);
    });
  }

  function ownKeys(object, enumerableOnly) { var keys = Object.keys(object); if (Object.getOwnPropertySymbols) { var symbols = Object.getOwnPropertySymbols(object); if (enumerableOnly) symbols = symbols.filter(function (sym) { return Object.getOwnPropertyDescriptor(object, sym).enumerable; }); keys.push.apply(keys, symbols); } return keys; }

  function _objectSpread(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; if (i % 2) { ownKeys(Object(source), true).forEach(function (key) { _defineProperty(target, key, source[key]); }); } else if (Object.getOwnPropertyDescriptors) { Object.defineProperties(target, Object.getOwnPropertyDescriptors(source)); } else { ownKeys(Object(source)).forEach(function (key) { Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key)); }); } } return target; }

  function _defineProperty(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
  function createDrop(manager) {
    return function drop() {
      var options = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};
      var monitor = manager.getMonitor();
      var registry = manager.getRegistry();
      verifyInvariants$1(monitor);
      var targetIds = getDroppableTargets(monitor); // Multiple actions are dispatched here, which is why this doesn't return an action

      targetIds.forEach(function (targetId, index) {
        var dropResult = determineDropResult(targetId, index, registry, monitor);
        var action = {
          type: DROP,
          payload: {
            dropResult: _objectSpread({}, options, {}, dropResult)
          }
        };
        manager.dispatch(action);
      });
    };
  }

  function verifyInvariants$1(monitor) {
    invariant(monitor.isDragging(), 'Cannot call drop while not dragging.');
    invariant(!monitor.didDrop(), 'Cannot call drop twice during one drag operation.');
  }

  function determineDropResult(targetId, index, registry, monitor) {
    var target = registry.getTarget(targetId);
    var dropResult = target ? target.drop(monitor, targetId) : undefined;
    verifyDropResultType(dropResult);

    if (typeof dropResult === 'undefined') {
      dropResult = index === 0 ? {} : monitor.getDropResult();
    }

    return dropResult;
  }

  function verifyDropResultType(dropResult) {
    invariant(typeof dropResult === 'undefined' || isObject(dropResult), 'Drop result must either be an object or undefined.');
  }

  function getDroppableTargets(monitor) {
    var targetIds = monitor.getTargetIds().filter(monitor.canDropOnTarget, monitor);
    targetIds.reverse();
    return targetIds;
  }

  function createEndDrag(manager) {
    return function endDrag() {
      var monitor = manager.getMonitor();
      var registry = manager.getRegistry();
      verifyIsDragging(monitor);
      var sourceId = monitor.getSourceId();
      var source = registry.getSource(sourceId, true);
      source.endDrag(monitor, sourceId);
      registry.unpinSource();
      return {
        type: END_DRAG
      };
    };
  }

  function verifyIsDragging(monitor) {
    invariant(monitor.isDragging(), 'Cannot call endDrag while not dragging.');
  }

  function createDragDropActions(manager) {
    return {
      beginDrag: createBeginDrag(manager),
      publishDragSource: createPublishDragSource(manager),
      hover: createHover(manager),
      drop: createDrop(manager),
      endDrag: createEndDrag(manager)
    };
  }

  var strictEquality = function strictEquality(a, b) {
    return a === b;
  };
  /**
   * Determine if two cartesian coordinate offsets are equal
   * @param offsetA
   * @param offsetB
   */

  function areCoordsEqual(offsetA, offsetB) {
    if (!offsetA && !offsetB) {
      return true;
    } else if (!offsetA || !offsetB) {
      return false;
    } else {
      return offsetA.x === offsetB.x && offsetA.y === offsetB.y;
    }
  }
  /**
   * Determines if two arrays of items are equal
   * @param a The first array of items
   * @param b The second array of items
   */

  function areArraysEqual(a, b) {
    var isEqual = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : strictEquality;

    if (a.length !== b.length) {
      return false;
    }

    for (var i = 0; i < a.length; ++i) {
      if (!isEqual(a[i], b[i])) {
        return false;
      }
    }

    return true;
  }

  function ownKeys$1(object, enumerableOnly) { var keys = Object.keys(object); if (Object.getOwnPropertySymbols) { var symbols = Object.getOwnPropertySymbols(object); if (enumerableOnly) symbols = symbols.filter(function (sym) { return Object.getOwnPropertyDescriptor(object, sym).enumerable; }); keys.push.apply(keys, symbols); } return keys; }

  function _objectSpread$1(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; if (i % 2) { ownKeys$1(Object(source), true).forEach(function (key) { _defineProperty$1(target, key, source[key]); }); } else if (Object.getOwnPropertyDescriptors) { Object.defineProperties(target, Object.getOwnPropertyDescriptors(source)); } else { ownKeys$1(Object(source)).forEach(function (key) { Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key)); }); } } return target; }

  function _defineProperty$1(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
  var initialState = {
    initialSourceClientOffset: null,
    initialClientOffset: null,
    clientOffset: null
  };
  function dragOffset() {
    var state = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : initialState;
    var action = arguments.length > 1 ? arguments[1] : undefined;
    var payload = action.payload;

    switch (action.type) {
      case INIT_COORDS:
      case BEGIN_DRAG:
        return {
          initialSourceClientOffset: payload.sourceClientOffset,
          initialClientOffset: payload.clientOffset,
          clientOffset: payload.clientOffset
        };

      case HOVER:
        if (areCoordsEqual(state.clientOffset, payload.clientOffset)) {
          return state;
        }

        return _objectSpread$1({}, state, {
          clientOffset: payload.clientOffset
        });

      case END_DRAG:
      case DROP:
        return initialState;

      default:
        return state;
    }
  }

  var ADD_SOURCE = 'dnd-core/ADD_SOURCE';
  var ADD_TARGET = 'dnd-core/ADD_TARGET';
  var REMOVE_SOURCE = 'dnd-core/REMOVE_SOURCE';
  var REMOVE_TARGET = 'dnd-core/REMOVE_TARGET';
  function addSource(sourceId) {
    return {
      type: ADD_SOURCE,
      payload: {
        sourceId: sourceId
      }
    };
  }
  function addTarget(targetId) {
    return {
      type: ADD_TARGET,
      payload: {
        targetId: targetId
      }
    };
  }
  function removeSource(sourceId) {
    return {
      type: REMOVE_SOURCE,
      payload: {
        sourceId: sourceId
      }
    };
  }
  function removeTarget(targetId) {
    return {
      type: REMOVE_TARGET,
      payload: {
        targetId: targetId
      }
    };
  }

  function ownKeys$2(object, enumerableOnly) { var keys = Object.keys(object); if (Object.getOwnPropertySymbols) { var symbols = Object.getOwnPropertySymbols(object); if (enumerableOnly) symbols = symbols.filter(function (sym) { return Object.getOwnPropertyDescriptor(object, sym).enumerable; }); keys.push.apply(keys, symbols); } return keys; }

  function _objectSpread$2(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; if (i % 2) { ownKeys$2(Object(source), true).forEach(function (key) { _defineProperty$2(target, key, source[key]); }); } else if (Object.getOwnPropertyDescriptors) { Object.defineProperties(target, Object.getOwnPropertyDescriptors(source)); } else { ownKeys$2(Object(source)).forEach(function (key) { Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key)); }); } } return target; }

  function _defineProperty$2(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
  var initialState$1 = {
    itemType: null,
    item: null,
    sourceId: null,
    targetIds: [],
    dropResult: null,
    didDrop: false,
    isSourcePublic: null
  };
  function dragOperation() {
    var state = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : initialState$1;
    var action = arguments.length > 1 ? arguments[1] : undefined;
    var payload = action.payload;

    switch (action.type) {
      case BEGIN_DRAG:
        return _objectSpread$2({}, state, {
          itemType: payload.itemType,
          item: payload.item,
          sourceId: payload.sourceId,
          isSourcePublic: payload.isSourcePublic,
          dropResult: null,
          didDrop: false
        });

      case PUBLISH_DRAG_SOURCE:
        return _objectSpread$2({}, state, {
          isSourcePublic: true
        });

      case HOVER:
        return _objectSpread$2({}, state, {
          targetIds: payload.targetIds
        });

      case REMOVE_TARGET:
        if (state.targetIds.indexOf(payload.targetId) === -1) {
          return state;
        }

        return _objectSpread$2({}, state, {
          targetIds: without(state.targetIds, payload.targetId)
        });

      case DROP:
        return _objectSpread$2({}, state, {
          dropResult: payload.dropResult,
          didDrop: true,
          targetIds: []
        });

      case END_DRAG:
        return _objectSpread$2({}, state, {
          itemType: null,
          item: null,
          sourceId: null,
          dropResult: null,
          didDrop: false,
          isSourcePublic: null,
          targetIds: []
        });

      default:
        return state;
    }
  }

  function refCount() {
    var state = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
    var action = arguments.length > 1 ? arguments[1] : undefined;

    switch (action.type) {
      case ADD_SOURCE:
      case ADD_TARGET:
        return state + 1;

      case REMOVE_SOURCE:
      case REMOVE_TARGET:
        return state - 1;

      default:
        return state;
    }
  }

  var NONE = [];
  var ALL = [];
  NONE.__IS_NONE__ = true;
  ALL.__IS_ALL__ = true;
  /**
   * Determines if the given handler IDs are dirty or not.
   *
   * @param dirtyIds The set of dirty handler ids
   * @param handlerIds The set of handler ids to check
   */

  function areDirty(dirtyIds, handlerIds) {
    if (dirtyIds === NONE) {
      return false;
    }

    if (dirtyIds === ALL || typeof handlerIds === 'undefined') {
      return true;
    }

    var commonIds = intersection(handlerIds, dirtyIds);
    return commonIds.length > 0;
  }

  function dirtyHandlerIds() {
    var action = arguments.length > 1 ? arguments[1] : undefined;

    switch (action.type) {
      case HOVER:
        break;

      case ADD_SOURCE:
      case ADD_TARGET:
      case REMOVE_TARGET:
      case REMOVE_SOURCE:
        return NONE;

      case BEGIN_DRAG:
      case PUBLISH_DRAG_SOURCE:
      case END_DRAG:
      case DROP:
      default:
        return ALL;
    }

    var _action$payload = action.payload,
        _action$payload$targe = _action$payload.targetIds,
        targetIds = _action$payload$targe === void 0 ? [] : _action$payload$targe,
        _action$payload$prevT = _action$payload.prevTargetIds,
        prevTargetIds = _action$payload$prevT === void 0 ? [] : _action$payload$prevT;
    var result = xor(targetIds, prevTargetIds);
    var didChange = result.length > 0 || !areArraysEqual(targetIds, prevTargetIds);

    if (!didChange) {
      return NONE;
    } // Check the target ids at the innermost position. If they are valid, add them
    // to the result


    var prevInnermostTargetId = prevTargetIds[prevTargetIds.length - 1];
    var innermostTargetId = targetIds[targetIds.length - 1];

    if (prevInnermostTargetId !== innermostTargetId) {
      if (prevInnermostTargetId) {
        result.push(prevInnermostTargetId);
      }

      if (innermostTargetId) {
        result.push(innermostTargetId);
      }
    }

    return result;
  }

  function stateId() {
    var state = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 0;
    return state + 1;
  }

  function ownKeys$3(object, enumerableOnly) { var keys = Object.keys(object); if (Object.getOwnPropertySymbols) { var symbols = Object.getOwnPropertySymbols(object); if (enumerableOnly) symbols = symbols.filter(function (sym) { return Object.getOwnPropertyDescriptor(object, sym).enumerable; }); keys.push.apply(keys, symbols); } return keys; }

  function _objectSpread$3(target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i] != null ? arguments[i] : {}; if (i % 2) { ownKeys$3(Object(source), true).forEach(function (key) { _defineProperty$3(target, key, source[key]); }); } else if (Object.getOwnPropertyDescriptors) { Object.defineProperties(target, Object.getOwnPropertyDescriptors(source)); } else { ownKeys$3(Object(source)).forEach(function (key) { Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key)); }); } } return target; }

  function _defineProperty$3(obj, key, value) { if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
  function reduce() {
    var state = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};
    var action = arguments.length > 1 ? arguments[1] : undefined;
    return {
      dirtyHandlerIds: dirtyHandlerIds(state.dirtyHandlerIds, {
        type: action.type,
        payload: _objectSpread$3({}, action.payload, {
          prevTargetIds: get(state, 'dragOperation.targetIds', [])
        })
      }),
      dragOffset: dragOffset(state.dragOffset, action),
      refCount: refCount(state.refCount, action),
      dragOperation: dragOperation(state.dragOperation, action),
      stateId: stateId(state.stateId)
    };
  }

  /**
   * Coordinate addition
   * @param a The first coordinate
   * @param b The second coordinate
   */
  function add(a, b) {
    return {
      x: a.x + b.x,
      y: a.y + b.y
    };
  }
  /**
   * Coordinate subtraction
   * @param a The first coordinate
   * @param b The second coordinate
   */

  function subtract(a, b) {
    return {
      x: a.x - b.x,
      y: a.y - b.y
    };
  }
  /**
   * Returns the cartesian distance of the drag source component's position, based on its position
   * at the time when the current drag operation has started, and the movement difference.
   *
   * Returns null if no item is being dragged.
   *
   * @param state The offset state to compute from
   */

  function getSourceClientOffset(state) {
    var clientOffset = state.clientOffset,
        initialClientOffset = state.initialClientOffset,
        initialSourceClientOffset = state.initialSourceClientOffset;

    if (!clientOffset || !initialClientOffset || !initialSourceClientOffset) {
      return null;
    }

    return subtract(add(clientOffset, initialSourceClientOffset), initialClientOffset);
  }
  /**
   * Determines the x,y offset between the client offset and the initial client offset
   *
   * @param state The offset state to compute from
   */

  function getDifferenceFromInitialOffset(state) {
    var clientOffset = state.clientOffset,
        initialClientOffset = state.initialClientOffset;

    if (!clientOffset || !initialClientOffset) {
      return null;
    }

    return subtract(clientOffset, initialClientOffset);
  }

  function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); return Constructor; }

  var DragDropMonitorImpl =
  /*#__PURE__*/
  function () {
    function DragDropMonitorImpl(store, registry) {
      _classCallCheck(this, DragDropMonitorImpl);

      this.store = store;
      this.registry = registry;
    }

    _createClass(DragDropMonitorImpl, [{
      key: "subscribeToStateChange",
      value: function subscribeToStateChange(listener) {
        var _this = this;

        var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
          handlerIds: undefined
        };
        var handlerIds = options.handlerIds;
        invariant(typeof listener === 'function', 'listener must be a function.');
        invariant(typeof handlerIds === 'undefined' || Array.isArray(handlerIds), 'handlerIds, when specified, must be an array of strings.');
        var prevStateId = this.store.getState().stateId;

        var handleChange = function handleChange() {
          var state = _this.store.getState();

          var currentStateId = state.stateId;

          try {
            var canSkipListener = currentStateId === prevStateId || currentStateId === prevStateId + 1 && !areDirty(state.dirtyHandlerIds, handlerIds);

            if (!canSkipListener) {
              listener();
            }
          } finally {
            prevStateId = currentStateId;
          }
        };

        return this.store.subscribe(handleChange);
      }
    }, {
      key: "subscribeToOffsetChange",
      value: function subscribeToOffsetChange(listener) {
        var _this2 = this;

        invariant(typeof listener === 'function', 'listener must be a function.');
        var previousState = this.store.getState().dragOffset;

        var handleChange = function handleChange() {
          var nextState = _this2.store.getState().dragOffset;

          if (nextState === previousState) {
            return;
          }

          previousState = nextState;
          listener();
        };

        return this.store.subscribe(handleChange);
      }
    }, {
      key: "canDragSource",
      value: function canDragSource(sourceId) {
        if (!sourceId) {
          return false;
        }

        var source = this.registry.getSource(sourceId);
        invariant(source, 'Expected to find a valid source.');

        if (this.isDragging()) {
          return false;
        }

        return source.canDrag(this, sourceId);
      }
    }, {
      key: "canDropOnTarget",
      value: function canDropOnTarget(targetId) {
        // undefined on initial render
        if (!targetId) {
          return false;
        }

        var target = this.registry.getTarget(targetId);
        invariant(target, 'Expected to find a valid target.');

        if (!this.isDragging() || this.didDrop()) {
          return false;
        }

        var targetType = this.registry.getTargetType(targetId);
        var draggedItemType = this.getItemType();
        return matchesType(targetType, draggedItemType) && target.canDrop(this, targetId);
      }
    }, {
      key: "isDragging",
      value: function isDragging() {
        return Boolean(this.getItemType());
      }
    }, {
      key: "isDraggingSource",
      value: function isDraggingSource(sourceId) {
        // undefined on initial render
        if (!sourceId) {
          return false;
        }

        var source = this.registry.getSource(sourceId, true);
        invariant(source, 'Expected to find a valid source.');

        if (!this.isDragging() || !this.isSourcePublic()) {
          return false;
        }

        var sourceType = this.registry.getSourceType(sourceId);
        var draggedItemType = this.getItemType();

        if (sourceType !== draggedItemType) {
          return false;
        }

        return source.isDragging(this, sourceId);
      }
    }, {
      key: "isOverTarget",
      value: function isOverTarget(targetId) {
        var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {
          shallow: false
        };

        // undefined on initial render
        if (!targetId) {
          return false;
        }

        var shallow = options.shallow;

        if (!this.isDragging()) {
          return false;
        }

        var targetType = this.registry.getTargetType(targetId);
        var draggedItemType = this.getItemType();

        if (draggedItemType && !matchesType(targetType, draggedItemType)) {
          return false;
        }

        var targetIds = this.getTargetIds();

        if (!targetIds.length) {
          return false;
        }

        var index = targetIds.indexOf(targetId);

        if (shallow) {
          return index === targetIds.length - 1;
        } else {
          return index > -1;
        }
      }
    }, {
      key: "getItemType",
      value: function getItemType() {
        return this.store.getState().dragOperation.itemType;
      }
    }, {
      key: "getItem",
      value: function getItem() {
        return this.store.getState().dragOperation.item;
      }
    }, {
      key: "getSourceId",
      value: function getSourceId() {
        return this.store.getState().dragOperation.sourceId;
      }
    }, {
      key: "getTargetIds",
      value: function getTargetIds() {
        return this.store.getState().dragOperation.targetIds;
      }
    }, {
      key: "getDropResult",
      value: function getDropResult() {
        return this.store.getState().dragOperation.dropResult;
      }
    }, {
      key: "didDrop",
      value: function didDrop() {
        return this.store.getState().dragOperation.didDrop;
      }
    }, {
      key: "isSourcePublic",
      value: function isSourcePublic() {
        return this.store.getState().dragOperation.isSourcePublic;
      }
    }, {
      key: "getInitialClientOffset",
      value: function getInitialClientOffset() {
        return this.store.getState().dragOffset.initialClientOffset;
      }
    }, {
      key: "getInitialSourceClientOffset",
      value: function getInitialSourceClientOffset() {
        return this.store.getState().dragOffset.initialSourceClientOffset;
      }
    }, {
      key: "getClientOffset",
      value: function getClientOffset() {
        return this.store.getState().dragOffset.clientOffset;
      }
    }, {
      key: "getSourceClientOffset",
      value: function getSourceClientOffset$1() {
        return getSourceClientOffset(this.store.getState().dragOffset);
      }
    }, {
      key: "getDifferenceFromInitialOffset",
      value: function getDifferenceFromInitialOffset$1() {
        return getDifferenceFromInitialOffset(this.store.getState().dragOffset);
      }
    }]);

    return DragDropMonitorImpl;
  }();

  var nextUniqueId = 0;
  function getNextUniqueId() {
    return nextUniqueId++;
  }

  function _typeof$1(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$1 = function _typeof(obj) { return typeof obj; }; } else { _typeof$1 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$1(obj); }
  function validateSourceContract(source) {
    invariant(typeof source.canDrag === 'function', 'Expected canDrag to be a function.');
    invariant(typeof source.beginDrag === 'function', 'Expected beginDrag to be a function.');
    invariant(typeof source.endDrag === 'function', 'Expected endDrag to be a function.');
  }
  function validateTargetContract(target) {
    invariant(typeof target.canDrop === 'function', 'Expected canDrop to be a function.');
    invariant(typeof target.hover === 'function', 'Expected hover to be a function.');
    invariant(typeof target.drop === 'function', 'Expected beginDrag to be a function.');
  }
  function validateType(type, allowArray) {
    if (allowArray && Array.isArray(type)) {
      type.forEach(function (t) {
        return validateType(t, false);
      });
      return;
    }

    invariant(typeof type === 'string' || _typeof$1(type) === 'symbol', allowArray ? 'Type can only be a string, a symbol, or an array of either.' : 'Type can only be a string or a symbol.');
  }

  // Use the fastest means possible to execute a task in its own turn, with
  // priority over other events including IO, animation, reflow, and redraw
  // events in browsers.
  //
  // An exception thrown by a task will permanently interrupt the processing of
  // subsequent tasks. The higher level `asap` function ensures that if an
  // exception is thrown by a task, that the task queue will continue flushing as
  // soon as possible, but if you use `rawAsap` directly, you are responsible to
  // either ensure that no exceptions are thrown from your task, or to manually
  // call `rawAsap.requestFlush` if an exception is thrown.
  function rawAsap(task) {
    if (!queue.length) {
      requestFlush();
    } // Equivalent to push, but avoids a function call.


    queue[queue.length] = task;
  }
  var queue = []; // Once a flush has been requested, no further calls to `requestFlush` are
  // off a `flush` event as quickly as possible. `flush` will attempt to exhaust
  // the event queue before yielding to the browser's own event loop.

  var requestFlush; // The position of the next task to execute in the task queue. This is
  // preserved between calls to `flush` so that it can be resumed if
  // a task throws an exception.

  var index = 0; // If a task schedules additional tasks recursively, the task queue can grow
  // unbounded. To prevent memory exhaustion, the task queue will periodically
  // truncate already-completed tasks.

  var capacity = 1024; // The flush function processes all tasks that have been scheduled with
  // `rawAsap` unless and until one of those tasks throws an exception.
  // If a task throws an exception, `flush` ensures that its state will remain
  // consistent and will resume where it left off when called again.
  // However, `flush` does not make any arrangements to be called again if an
  // exception is thrown.

  function flush() {
    while (index < queue.length) {
      var currentIndex = index; // Advance the index before calling the task. This ensures that we will
      // begin flushing on the next task the task throws an error.

      index = index + 1;
      queue[currentIndex].call(); // Prevent leaking memory for long chains of recursive calls to `asap`.
      // If we call `asap` within tasks scheduled by `asap`, the queue will
      // grow, but to avoid an O(n) walk for every task we execute, we don't
      // shift tasks off the queue after they have been executed.
      // Instead, we periodically shift 1024 tasks off the queue.

      if (index > capacity) {
        // Manually shift all values starting at the index back to the
        // beginning of the queue.
        for (var scan = 0, newLength = queue.length - index; scan < newLength; scan++) {
          queue[scan] = queue[scan + index];
        }

        queue.length -= index;
        index = 0;
      }
    }

    queue.length = 0;
    index = 0;
  } // `requestFlush` is implemented using a strategy based on data collected from
  // every available SauceLabs Selenium web driver worker at time of writing.
  // https://docs.google.com/spreadsheets/d/1mG-5UYGup5qxGdEMWkhP6BWCz053NUb2E1QoUTU16uA/edit#gid=783724593
  // Safari 6 and 6.1 for desktop, iPad, and iPhone are the only browsers that
  // have WebKitMutationObserver but not un-prefixed MutationObserver.
  // Must use `global` or `self` instead of `window` to work in both frames and web
  // workers. `global` is a provision of Browserify, Mr, Mrs, or Mop.

  /* globals self */


  var scope = typeof global !== 'undefined' ? global : self;
  var BrowserMutationObserver = scope.MutationObserver || scope.WebKitMutationObserver; // MutationObservers are desirable because they have high priority and work
  // reliably everywhere they are implemented.
  // They are implemented in all modern browsers.
  //
  // - Android 4-4.3
  // - Chrome 26-34
  // - Firefox 14-29
  // - Internet Explorer 11
  // - iPad Safari 6-7.1
  // - iPhone Safari 7-7.1
  // - Safari 6-7

  if (typeof BrowserMutationObserver === 'function') {
    requestFlush = makeRequestCallFromMutationObserver(flush); // MessageChannels are desirable because they give direct access to the HTML
    // task queue, are implemented in Internet Explorer 10, Safari 5.0-1, and Opera
    // 11-12, and in web workers in many engines.
    // Although message channels yield to any queued rendering and IO tasks, they
    // would be better than imposing the 4ms delay of timers.
    // However, they do not work reliably in Internet Explorer or Safari.
    // Internet Explorer 10 is the only browser that has setImmediate but does
    // not have MutationObservers.
    // Although setImmediate yields to the browser's renderer, it would be
    // preferrable to falling back to setTimeout since it does not have
    // the minimum 4ms penalty.
    // Unfortunately there appears to be a bug in Internet Explorer 10 Mobile (and
    // Desktop to a lesser extent) that renders both setImmediate and
    // MessageChannel useless for the purposes of ASAP.
    // https://github.com/kriskowal/q/issues/396
    // Timers are implemented universally.
    // We fall back to timers in workers in most engines, and in foreground
    // contexts in the following browsers.
    // However, note that even this simple case requires nuances to operate in a
    // broad spectrum of browsers.
    //
    // - Firefox 3-13
    // - Internet Explorer 6-9
    // - iPad Safari 4.3
    // - Lynx 2.8.7
  } else {
    requestFlush = makeRequestCallFromTimer(flush);
  } // `requestFlush` requests that the high priority event queue be flushed as
  // soon as possible.
  // This is useful to prevent an error thrown in a task from stalling the event
  // queue if the exception handled by Node.js’s
  // `process.on("uncaughtException")` or by a domain.


  rawAsap.requestFlush = requestFlush; // To request a high priority event, we induce a mutation observer by toggling
  // the text of a text node between "1" and "-1".

  function makeRequestCallFromMutationObserver(callback) {
    var toggle = 1;
    var observer = new BrowserMutationObserver(callback);
    var node = document.createTextNode('');
    observer.observe(node, {
      characterData: true
    });
    return function requestCall() {
      toggle = -toggle;
      node.data = toggle;
    };
  } // The message channel technique was discovered by Malte Ubl and was the
  // original foundation for this library.
  // http://www.nonblocking.io/2011/06/windownexttick.html
  // Safari 6.0.5 (at least) intermittently fails to create message ports on a
  // page's first load. Thankfully, this version of Safari supports
  // MutationObservers, so we don't need to fall back in that case.
  // function makeRequestCallFromMessageChannel(callback) {
  //     var channel = new MessageChannel();
  //     channel.port1.onmessage = callback;
  //     return function requestCall() {
  //         channel.port2.postMessage(0);
  //     };
  // }
  // For reasons explained above, we are also unable to use `setImmediate`
  // under any circumstances.
  // Even if we were, there is another bug in Internet Explorer 10.
  // It is not sufficient to assign `setImmediate` to `requestFlush` because
  // `setImmediate` must be called *by name* and therefore must be wrapped in a
  // closure.
  // Never forget.
  // function makeRequestCallFromSetImmediate(callback) {
  //     return function requestCall() {
  //         setImmediate(callback);
  //     };
  // }
  // Safari 6.0 has a problem where timers will get lost while the user is
  // scrolling. This problem does not impact ASAP because Safari 6.0 supports
  // mutation observers, so that implementation is used instead.
  // However, if we ever elect to use timers in Safari, the prevalent work-around
  // is to add a scroll event listener that calls for a flush.
  // `setTimeout` does not call the passed callback if the delay is less than
  // approximately 7 in web workers in Firefox 8 through 18, and sometimes not
  // even then.


  function makeRequestCallFromTimer(callback) {
    return function requestCall() {
      // We dispatch a timeout with a specified delay of 0 for engines that
      // can reliably accommodate that request. This will usually be snapped
      // to a 4 milisecond delay, but once we're flushing, there's no delay
      // between events.
      var timeoutHandle = setTimeout(handleTimer, 0); // However, since this timer gets frequently dropped in Firefox
      // workers, we enlist an interval handle that will try to fire
      // an event 20 times per second until it succeeds.

      var intervalHandle = setInterval(handleTimer, 50);

      function handleTimer() {
        // Whichever timer succeeds will cancel both timers and
        // execute the callback.
        clearTimeout(timeoutHandle);
        clearInterval(intervalHandle);
        callback();
      }
    };
  } // This is for `asap.js` only.
  // Its name will be periodically randomized to break any code that depends on
  // its existence.


  rawAsap.makeRequestCallFromTimer = makeRequestCallFromTimer; // ASAP was originally a nextTick shim included in Q. This was factored out
  // into this ASAP package. It was later adapted to RSVP which made further
  // amendments. These decisions, particularly to marginalize MessageChannel and
  // to capture the MutationObserver implementation in a closure, were integrated
  // back into ASAP proper.
  // https://github.com/tildeio/rsvp.js/blob/cddf7232546a9cf858524b75cde6f9edf72620a7/lib/rsvp/asap.js

  // RawTasks are recycled to reduce GC churn.

  var freeTasks = []; // We queue errors to ensure they are thrown in right order (FIFO).
  // Array-as-queue is good enough here, since we are just dealing with exceptions.

  var pendingErrors = [];
  var requestErrorThrow = rawAsap.makeRequestCallFromTimer(throwFirstError);

  function throwFirstError() {
    if (pendingErrors.length) {
      throw pendingErrors.shift();
    }
  }
  /**
   * Calls a task as soon as possible after returning, in its own event, with priority
   * over other events like animation, reflow, and repaint. An error thrown from an
   * event will not interrupt, nor even substantially slow down the processing of
   * other events, but will be rather postponed to a lower priority event.
   * @param {{call}} task A callable object, typically a function that takes no
   * arguments.
   */


  function asap(task) {
    var rawTask;

    if (freeTasks.length) {
      rawTask = freeTasks.pop();
    } else {
      rawTask = new RawTask();
    }

    rawTask.task = task;
    rawAsap(rawTask);
  } // We wrap tasks with recyclable task objects.  A task object implements
  // `call`, just like a function.

  var RawTask =
  /** @class */
  function () {
    function RawTask() {}

    RawTask.prototype.call = function () {
      try {
        this.task.call();
      } catch (error) {
        if (asap.onerror) {
          // This hook exists purely for testing purposes.
          // Its name will be periodically randomized to break any code that
          // depends on its existence.
          asap.onerror(error);
        } else {
          // In a web browser, exceptions are not fatal. However, to avoid
          // slowing down the queue of pending tasks, we rethrow the error in a
          // lower priority turn.
          pendingErrors.push(error);
          requestErrorThrow();
        }
      } finally {
        this.task = null;
        freeTasks[freeTasks.length] = this;
      }
    };

    return RawTask;
  }();

  function _classCallCheck$1(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$1(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$1(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$1(Constructor.prototype, protoProps); if (staticProps) _defineProperties$1(Constructor, staticProps); return Constructor; }

  function _slicedToArray(arr, i) { return _arrayWithHoles(arr) || _iterableToArrayLimit(arr, i) || _nonIterableRest(); }

  function _nonIterableRest() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles(arr) { if (Array.isArray(arr)) return arr; }

  function getNextHandlerId(role) {
    var id = getNextUniqueId().toString();

    switch (role) {
      case HandlerRole.SOURCE:
        return "S".concat(id);

      case HandlerRole.TARGET:
        return "T".concat(id);

      default:
        throw new Error("Unknown Handler Role: ".concat(role));
    }
  }

  function parseRoleFromHandlerId(handlerId) {
    switch (handlerId[0]) {
      case 'S':
        return HandlerRole.SOURCE;

      case 'T':
        return HandlerRole.TARGET;

      default:
        invariant(false, "Cannot parse handler ID: ".concat(handlerId));
    }
  }

  function mapContainsValue(map, searchValue) {
    var entries = map.entries();
    var isDone = false;

    do {
      var _entries$next = entries.next(),
          done = _entries$next.done,
          _entries$next$value = _slicedToArray(_entries$next.value, 2),
          value = _entries$next$value[1];

      if (value === searchValue) {
        return true;
      }

      isDone = !!done;
    } while (!isDone);

    return false;
  }

  var HandlerRegistryImpl =
  /*#__PURE__*/
  function () {
    function HandlerRegistryImpl(store) {
      _classCallCheck$1(this, HandlerRegistryImpl);

      this.types = new Map();
      this.dragSources = new Map();
      this.dropTargets = new Map();
      this.pinnedSourceId = null;
      this.pinnedSource = null;
      this.store = store;
    }

    _createClass$1(HandlerRegistryImpl, [{
      key: "addSource",
      value: function addSource$1(type, source) {
        validateType(type);
        validateSourceContract(source);
        var sourceId = this.addHandler(HandlerRole.SOURCE, type, source);
        this.store.dispatch(addSource(sourceId));
        return sourceId;
      }
    }, {
      key: "addTarget",
      value: function addTarget$1(type, target) {
        validateType(type, true);
        validateTargetContract(target);
        var targetId = this.addHandler(HandlerRole.TARGET, type, target);
        this.store.dispatch(addTarget(targetId));
        return targetId;
      }
    }, {
      key: "containsHandler",
      value: function containsHandler(handler) {
        return mapContainsValue(this.dragSources, handler) || mapContainsValue(this.dropTargets, handler);
      }
    }, {
      key: "getSource",
      value: function getSource(sourceId) {
        var includePinned = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : false;
        invariant(this.isSourceId(sourceId), 'Expected a valid source ID.');
        var isPinned = includePinned && sourceId === this.pinnedSourceId;
        var source = isPinned ? this.pinnedSource : this.dragSources.get(sourceId);
        return source;
      }
    }, {
      key: "getTarget",
      value: function getTarget(targetId) {
        invariant(this.isTargetId(targetId), 'Expected a valid target ID.');
        return this.dropTargets.get(targetId);
      }
    }, {
      key: "getSourceType",
      value: function getSourceType(sourceId) {
        invariant(this.isSourceId(sourceId), 'Expected a valid source ID.');
        return this.types.get(sourceId);
      }
    }, {
      key: "getTargetType",
      value: function getTargetType(targetId) {
        invariant(this.isTargetId(targetId), 'Expected a valid target ID.');
        return this.types.get(targetId);
      }
    }, {
      key: "isSourceId",
      value: function isSourceId(handlerId) {
        var role = parseRoleFromHandlerId(handlerId);
        return role === HandlerRole.SOURCE;
      }
    }, {
      key: "isTargetId",
      value: function isTargetId(handlerId) {
        var role = parseRoleFromHandlerId(handlerId);
        return role === HandlerRole.TARGET;
      }
    }, {
      key: "removeSource",
      value: function removeSource$1(sourceId) {
        var _this = this;

        invariant(this.getSource(sourceId), 'Expected an existing source.');
        this.store.dispatch(removeSource(sourceId));
        asap(function () {
          _this.dragSources.delete(sourceId);

          _this.types.delete(sourceId);
        });
      }
    }, {
      key: "removeTarget",
      value: function removeTarget$1(targetId) {
        invariant(this.getTarget(targetId), 'Expected an existing target.');
        this.store.dispatch(removeTarget(targetId));
        this.dropTargets.delete(targetId);
        this.types.delete(targetId);
      }
    }, {
      key: "pinSource",
      value: function pinSource(sourceId) {
        var source = this.getSource(sourceId);
        invariant(source, 'Expected an existing source.');
        this.pinnedSourceId = sourceId;
        this.pinnedSource = source;
      }
    }, {
      key: "unpinSource",
      value: function unpinSource() {
        invariant(this.pinnedSource, 'No source is pinned at the time.');
        this.pinnedSourceId = null;
        this.pinnedSource = null;
      }
    }, {
      key: "addHandler",
      value: function addHandler(role, type, handler) {
        var id = getNextHandlerId(role);
        this.types.set(id, type);

        if (role === HandlerRole.SOURCE) {
          this.dragSources.set(id, handler);
        } else if (role === HandlerRole.TARGET) {
          this.dropTargets.set(id, handler);
        }

        return id;
      }
    }]);

    return HandlerRegistryImpl;
  }();

  function _classCallCheck$2(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$2(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$2(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$2(Constructor.prototype, protoProps); if (staticProps) _defineProperties$2(Constructor, staticProps); return Constructor; }

  function makeStoreInstance(debugMode) {
    // TODO: if we ever make a react-native version of this,
    // we'll need to consider how to pull off dev-tooling
    var reduxDevTools = typeof window !== 'undefined' && window.__REDUX_DEVTOOLS_EXTENSION__;
    return createStore(reduce, debugMode && reduxDevTools && reduxDevTools({
      name: 'dnd-core',
      instanceId: 'dnd-core'
    }));
  }

  var DragDropManagerImpl =
  /*#__PURE__*/
  function () {
    function DragDropManagerImpl() {
      var _this = this;

      var debugMode = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : false;

      _classCallCheck$2(this, DragDropManagerImpl);

      this.isSetUp = false;

      this.handleRefCountChange = function () {
        var shouldSetUp = _this.store.getState().refCount > 0;

        if (_this.backend) {
          if (shouldSetUp && !_this.isSetUp) {
            _this.backend.setup();

            _this.isSetUp = true;
          } else if (!shouldSetUp && _this.isSetUp) {
            _this.backend.teardown();

            _this.isSetUp = false;
          }
        }
      };

      var store = makeStoreInstance(debugMode);
      this.store = store;
      this.monitor = new DragDropMonitorImpl(store, new HandlerRegistryImpl(store));
      store.subscribe(this.handleRefCountChange);
    }

    _createClass$2(DragDropManagerImpl, [{
      key: "receiveBackend",
      value: function receiveBackend(backend) {
        this.backend = backend;
      }
    }, {
      key: "getMonitor",
      value: function getMonitor() {
        return this.monitor;
      }
    }, {
      key: "getBackend",
      value: function getBackend() {
        return this.backend;
      }
    }, {
      key: "getRegistry",
      value: function getRegistry() {
        return this.monitor.registry;
      }
    }, {
      key: "getActions",
      value: function getActions() {
        /* eslint-disable-next-line @typescript-eslint/no-this-alias */
        var manager = this;
        var dispatch = this.store.dispatch;

        function bindActionCreator(actionCreator) {
          return function () {
            for (var _len = arguments.length, args = new Array(_len), _key = 0; _key < _len; _key++) {
              args[_key] = arguments[_key];
            }

            var action = actionCreator.apply(manager, args);

            if (typeof action !== 'undefined') {
              dispatch(action);
            }
          };
        }

        var actions = createDragDropActions(this);
        return Object.keys(actions).reduce(function (boundActions, key) {
          var action = actions[key];
          boundActions[key] = bindActionCreator(action);
          return boundActions;
        }, {});
      }
    }, {
      key: "dispatch",
      value: function dispatch(action) {
        this.store.dispatch(action);
      }
    }]);

    return DragDropManagerImpl;
  }();

  function createDragDropManager(backendFactory, globalContext, backendOptions, debugMode) {
    var manager = new DragDropManagerImpl(debugMode);
    var backend = backendFactory(manager, globalContext, backendOptions);
    manager.receiveBackend(backend);
    return manager;
  }

  /**
   * Create the React Context
   */

  var DndContext = React.createContext({
    dragDropManager: undefined
  });
  /**
   * Creates the context object we're providing
   * @param backend
   * @param context
   */

  function createDndContext(backend, context, options, debugMode) {
    return {
      dragDropManager: createDragDropManager(backend, context, options, debugMode)
    };
  }

  function _slicedToArray$1(arr, i) { return _arrayWithHoles$1(arr) || _iterableToArrayLimit$1(arr, i) || _nonIterableRest$1(); }

  function _nonIterableRest$1() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$1(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$1(arr) { if (Array.isArray(arr)) return arr; }

  function _objectWithoutProperties(source, excluded) { if (source == null) return {}; var target = _objectWithoutPropertiesLoose(source, excluded); var key, i; if (Object.getOwnPropertySymbols) { var sourceSymbolKeys = Object.getOwnPropertySymbols(source); for (i = 0; i < sourceSymbolKeys.length; i++) { key = sourceSymbolKeys[i]; if (excluded.indexOf(key) >= 0) continue; if (!Object.prototype.propertyIsEnumerable.call(source, key)) continue; target[key] = source[key]; } } return target; }

  function _objectWithoutPropertiesLoose(source, excluded) { if (source == null) return {}; var target = {}; var sourceKeys = Object.keys(source); var key, i; for (i = 0; i < sourceKeys.length; i++) { key = sourceKeys[i]; if (excluded.indexOf(key) >= 0) continue; target[key] = source[key]; } return target; }
  var refCount$1 = 0;
  /**
   * A React component that provides the React-DnD context
   */

  var DndProvider = React.memo(function (_ref) {
    var children = _ref.children,
        props = _objectWithoutProperties(_ref, ["children"]);

    var _getDndContextValue = getDndContextValue(props),
        _getDndContextValue2 = _slicedToArray$1(_getDndContextValue, 2),
        manager = _getDndContextValue2[0],
        isGlobalInstance = _getDndContextValue2[1]; // memoized from props

    /**
     * If the global context was used to store the DND context
     * then where theres no more references to it we should
     * clean it up to avoid memory leaks
     */


    React.useEffect(function () {
      if (isGlobalInstance) {
        refCount$1++;
      }

      return function () {
        if (isGlobalInstance) {
          refCount$1--;

          if (refCount$1 === 0) {
            var context = getGlobalContext();
            context[instanceSymbol] = null;
          }
        }
      };
    }, []);
    return React.createElement(DndContext.Provider, {
      value: manager
    }, children);
  });
  DndProvider.displayName = 'DndProvider';

  function getDndContextValue(props) {
    if ('manager' in props) {
      var _manager = {
        dragDropManager: props.manager
      };
      return [_manager, false];
    }

    var manager = createSingletonDndContext(props.backend, props.context, props.options, props.debugMode);
    var isGlobalInstance = !props.context;
    return [manager, isGlobalInstance];
  }

  var instanceSymbol = Symbol.for('__REACT_DND_CONTEXT_INSTANCE__');

  function createSingletonDndContext(backend) {
    var context = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : getGlobalContext();
    var options = arguments.length > 2 ? arguments[2] : undefined;
    var debugMode = arguments.length > 3 ? arguments[3] : undefined;
    var ctx = context;

    if (!ctx[instanceSymbol]) {
      ctx[instanceSymbol] = createDndContext(backend, context, options, debugMode);
    }

    return ctx[instanceSymbol];
  }

  function getGlobalContext() {
    return typeof global !== 'undefined' ? global : window;
  }

  /*
   * A utility for rendering a drag preview image
   */

  var DragPreviewImage = React.memo(function (_ref) {
    var connect = _ref.connect,
        src = _ref.src;

    if (typeof Image !== 'undefined') {
      var img = new Image();
      img.src = src;

      img.onload = function () {
        return connect(img);
      };
    }

    return null;
  });
  DragPreviewImage.displayName = 'DragPreviewImage';

  var useIsomorphicLayoutEffect = typeof window !== 'undefined' ? React.useLayoutEffect : React.useEffect;

  function shallowEqual(objA, objB, compare, compareContext) {
    var compareResult = compare ? compare.call(compareContext, objA, objB) : void 0;

    if (compareResult !== void 0) {
      return !!compareResult;
    }

    if (objA === objB) {
      return true;
    }

    if (typeof objA !== 'object' || !objA || typeof objB !== 'object' || !objB) {
      return false;
    }

    var keysA = Object.keys(objA);
    var keysB = Object.keys(objB);

    if (keysA.length !== keysB.length) {
      return false;
    }

    var bHasOwnProperty = Object.prototype.hasOwnProperty.bind(objB); // Test for A's keys different from B.

    for (var idx = 0; idx < keysA.length; idx++) {
      var key = keysA[idx];

      if (!bHasOwnProperty(key)) {
        return false;
      }

      var valueA = objA[key];
      var valueB = objB[key];
      compareResult = compare ? compare.call(compareContext, valueA, valueB, key) : void 0;

      if (compareResult === false || compareResult === void 0 && valueA !== valueB) {
        return false;
      }
    }

    return true;
  }

  function _slicedToArray$2(arr, i) { return _arrayWithHoles$2(arr) || _iterableToArrayLimit$2(arr, i) || _nonIterableRest$2(); }

  function _nonIterableRest$2() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$2(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$2(arr) { if (Array.isArray(arr)) return arr; }
  /**
   *
   * @param monitor The monitor to collect state from
   * @param collect The collecting function
   * @param onUpdate A method to invoke when updates occur
   */

  function useCollector(monitor, collect, onUpdate) {
    var _useState = React.useState(function () {
      return collect(monitor);
    }),
        _useState2 = _slicedToArray$2(_useState, 2),
        collected = _useState2[0],
        setCollected = _useState2[1];

    var updateCollected = React.useCallback(function () {
      var nextValue = collect(monitor);

      if (!shallowEqual(collected, nextValue)) {
        setCollected(nextValue);

        if (onUpdate) {
          onUpdate();
        }
      }
    }, [collected, monitor, onUpdate]); // update the collected properties after the first render
    // and the components are attached to dnd-core

    useIsomorphicLayoutEffect(updateCollected, []);
    return [collected, updateCollected];
  }

  function _slicedToArray$3(arr, i) { return _arrayWithHoles$3(arr) || _iterableToArrayLimit$3(arr, i) || _nonIterableRest$3(); }

  function _nonIterableRest$3() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$3(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$3(arr) { if (Array.isArray(arr)) return arr; }
  function useMonitorOutput(monitor, collect, onCollect) {
    var _useCollector = useCollector(monitor, collect, onCollect),
        _useCollector2 = _slicedToArray$3(_useCollector, 2),
        collected = _useCollector2[0],
        updateCollected = _useCollector2[1];

    useIsomorphicLayoutEffect(function subscribeToMonitorStateChange() {
      var handlerId = monitor.getHandlerId();

      if (handlerId == null) {
        return undefined;
      }

      return monitor.subscribeToStateChange(updateCollected, {
        handlerIds: [handlerId]
      });
    }, [monitor, updateCollected]);
    return collected;
  }

  function registerTarget(type, target, manager) {
    var registry = manager.getRegistry();
    var targetId = registry.addTarget(type, target);
    return [targetId, function () {
      return registry.removeTarget(targetId);
    }];
  }
  function registerSource(type, source, manager) {
    var registry = manager.getRegistry();
    var sourceId = registry.addSource(type, source);
    return [sourceId, function () {
      return registry.removeSource(sourceId);
    }];
  }

  /**
   * A hook to retrieve the DragDropManager from Context
   */

  function useDragDropManager() {
    var _useContext = React.useContext(DndContext),
        dragDropManager = _useContext.dragDropManager;

    invariant(dragDropManager != null, 'Expected drag drop context');
    return dragDropManager;
  }

  function _classCallCheck$3(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$3(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$3(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$3(Constructor.prototype, protoProps); if (staticProps) _defineProperties$3(Constructor, staticProps); return Constructor; }
  var isCallingCanDrag = false;
  var isCallingIsDragging = false;
  var DragSourceMonitorImpl =
  /*#__PURE__*/
  function () {
    function DragSourceMonitorImpl(manager) {
      _classCallCheck$3(this, DragSourceMonitorImpl);

      this.sourceId = null;
      this.internalMonitor = manager.getMonitor();
    }

    _createClass$3(DragSourceMonitorImpl, [{
      key: "receiveHandlerId",
      value: function receiveHandlerId(sourceId) {
        this.sourceId = sourceId;
      }
    }, {
      key: "getHandlerId",
      value: function getHandlerId() {
        return this.sourceId;
      }
    }, {
      key: "canDrag",
      value: function canDrag() {
        invariant(!isCallingCanDrag, 'You may not call monitor.canDrag() inside your canDrag() implementation. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source-monitor');

        try {
          isCallingCanDrag = true;
          return this.internalMonitor.canDragSource(this.sourceId);
        } finally {
          isCallingCanDrag = false;
        }
      }
    }, {
      key: "isDragging",
      value: function isDragging() {
        if (!this.sourceId) {
          return false;
        }

        invariant(!isCallingIsDragging, 'You may not call monitor.isDragging() inside your isDragging() implementation. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source-monitor');

        try {
          isCallingIsDragging = true;
          return this.internalMonitor.isDraggingSource(this.sourceId);
        } finally {
          isCallingIsDragging = false;
        }
      }
    }, {
      key: "subscribeToStateChange",
      value: function subscribeToStateChange(listener, options) {
        return this.internalMonitor.subscribeToStateChange(listener, options);
      }
    }, {
      key: "isDraggingSource",
      value: function isDraggingSource(sourceId) {
        return this.internalMonitor.isDraggingSource(sourceId);
      }
    }, {
      key: "isOverTarget",
      value: function isOverTarget(targetId, options) {
        return this.internalMonitor.isOverTarget(targetId, options);
      }
    }, {
      key: "getTargetIds",
      value: function getTargetIds() {
        return this.internalMonitor.getTargetIds();
      }
    }, {
      key: "isSourcePublic",
      value: function isSourcePublic() {
        return this.internalMonitor.isSourcePublic();
      }
    }, {
      key: "getSourceId",
      value: function getSourceId() {
        return this.internalMonitor.getSourceId();
      }
    }, {
      key: "subscribeToOffsetChange",
      value: function subscribeToOffsetChange(listener) {
        return this.internalMonitor.subscribeToOffsetChange(listener);
      }
    }, {
      key: "canDragSource",
      value: function canDragSource(sourceId) {
        return this.internalMonitor.canDragSource(sourceId);
      }
    }, {
      key: "canDropOnTarget",
      value: function canDropOnTarget(targetId) {
        return this.internalMonitor.canDropOnTarget(targetId);
      }
    }, {
      key: "getItemType",
      value: function getItemType() {
        return this.internalMonitor.getItemType();
      }
    }, {
      key: "getItem",
      value: function getItem() {
        return this.internalMonitor.getItem();
      }
    }, {
      key: "getDropResult",
      value: function getDropResult() {
        return this.internalMonitor.getDropResult();
      }
    }, {
      key: "didDrop",
      value: function didDrop() {
        return this.internalMonitor.didDrop();
      }
    }, {
      key: "getInitialClientOffset",
      value: function getInitialClientOffset() {
        return this.internalMonitor.getInitialClientOffset();
      }
    }, {
      key: "getInitialSourceClientOffset",
      value: function getInitialSourceClientOffset() {
        return this.internalMonitor.getInitialSourceClientOffset();
      }
    }, {
      key: "getSourceClientOffset",
      value: function getSourceClientOffset() {
        return this.internalMonitor.getSourceClientOffset();
      }
    }, {
      key: "getClientOffset",
      value: function getClientOffset() {
        return this.internalMonitor.getClientOffset();
      }
    }, {
      key: "getDifferenceFromInitialOffset",
      value: function getDifferenceFromInitialOffset() {
        return this.internalMonitor.getDifferenceFromInitialOffset();
      }
    }]);

    return DragSourceMonitorImpl;
  }();

  function setRef(ref, node) {
    if (typeof ref === 'function') {
      ref(node);
    } else {
      ref.current = node;
    }
  }

  function cloneWithRef(element, newRef) {
    var previousRef = element.ref;
    invariant(typeof previousRef !== 'string', 'Cannot connect React DnD to an element with an existing string ref. ' + 'Please convert it to use a callback ref instead, or wrap it into a <span> or <div>. ' + 'Read more: https://facebook.github.io/react/docs/more-about-refs.html#the-ref-callback-attribute');

    if (!previousRef) {
      // When there is no ref on the element, use the new ref directly
      return React.cloneElement(element, {
        ref: newRef
      });
    } else {
      return React.cloneElement(element, {
        ref: function ref(node) {
          setRef(previousRef, node);
          setRef(newRef, node);
        }
      });
    }
  }

  function throwIfCompositeComponentElement(element) {
    // Custom components can no longer be wrapped directly in React DnD 2.0
    // so that we don't need to depend on findDOMNode() from react-dom.
    if (typeof element.type === 'string') {
      return;
    }

    var displayName = element.type.displayName || element.type.name || 'the component';
    throw new Error('Only native element nodes can now be passed to React DnD connectors.' + "You can either wrap ".concat(displayName, " into a <div>, or turn it into a ") + 'drag source or a drop target itself.');
  }

  function wrapHookToRecognizeElement(hook) {
    return function () {
      var elementOrNode = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : null;
      var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : null;

      // When passed a node, call the hook straight away.
      if (!React.isValidElement(elementOrNode)) {
        var node = elementOrNode;
        hook(node, options); // return the node so it can be chained (e.g. when within callback refs
        // <div ref={node => connectDragSource(connectDropTarget(node))}/>

        return node;
      } // If passed a ReactElement, clone it and attach this function as a ref.
      // This helps us achieve a neat API where user doesn't even know that refs
      // are being used under the hood.


      var element = elementOrNode;
      throwIfCompositeComponentElement(element); // When no options are passed, use the hook directly

      var ref = options ? function (node) {
        return hook(node, options);
      } : hook;
      return cloneWithRef(element, ref);
    };
  }

  function wrapConnectorHooks(hooks) {
    var wrappedHooks = {};
    Object.keys(hooks).forEach(function (key) {
      var hook = hooks[key]; // ref objects should be passed straight through without wrapping

      if (key.endsWith('Ref')) {
        wrappedHooks[key] = hooks[key];
      } else {
        var wrappedHook = wrapHookToRecognizeElement(hook);

        wrappedHooks[key] = function () {
          return wrappedHook;
        };
      }
    });
    return wrappedHooks;
  }

  function _typeof$2(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$2 = function _typeof(obj) { return typeof obj; }; } else { _typeof$2 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$2(obj); }

  function isRef(obj) {
    return (// eslint-disable-next-line no-prototype-builtins
      obj !== null && _typeof$2(obj) === 'object' && obj.hasOwnProperty('current')
    );
  }

  function _classCallCheck$4(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$4(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$4(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$4(Constructor.prototype, protoProps); if (staticProps) _defineProperties$4(Constructor, staticProps); return Constructor; }
  var SourceConnector =
  /*#__PURE__*/
  function () {
    function SourceConnector(backend) {
      var _this = this;

      _classCallCheck$4(this, SourceConnector);

      this.hooks = wrapConnectorHooks({
        dragSource: function dragSource(node, options) {
          _this.clearDragSource();

          _this.dragSourceOptions = options || null;

          if (isRef(node)) {
            _this.dragSourceRef = node;
          } else {
            _this.dragSourceNode = node;
          }

          _this.reconnectDragSource();
        },
        dragPreview: function dragPreview(node, options) {
          _this.clearDragPreview();

          _this.dragPreviewOptions = options || null;

          if (isRef(node)) {
            _this.dragPreviewRef = node;
          } else {
            _this.dragPreviewNode = node;
          }

          _this.reconnectDragPreview();
        }
      });
      this.handlerId = null; // The drop target may either be attached via ref or connect function

      this.dragSourceRef = null;
      this.dragSourceOptionsInternal = null; // The drag preview may either be attached via ref or connect function

      this.dragPreviewRef = null;
      this.dragPreviewOptionsInternal = null;
      this.lastConnectedHandlerId = null;
      this.lastConnectedDragSource = null;
      this.lastConnectedDragSourceOptions = null;
      this.lastConnectedDragPreview = null;
      this.lastConnectedDragPreviewOptions = null;
      this.backend = backend;
    }

    _createClass$4(SourceConnector, [{
      key: "receiveHandlerId",
      value: function receiveHandlerId(newHandlerId) {
        if (this.handlerId === newHandlerId) {
          return;
        }

        this.handlerId = newHandlerId;
        this.reconnect();
      }
    }, {
      key: "reconnect",
      value: function reconnect() {
        this.reconnectDragSource();
        this.reconnectDragPreview();
      }
    }, {
      key: "reconnectDragSource",
      value: function reconnectDragSource() {
        var dragSource = this.dragSource; // if nothing has changed then don't resubscribe

        var didChange = this.didHandlerIdChange() || this.didConnectedDragSourceChange() || this.didDragSourceOptionsChange();

        if (didChange) {
          this.disconnectDragSource();
        }

        if (!this.handlerId) {
          return;
        }

        if (!dragSource) {
          this.lastConnectedDragSource = dragSource;
          return;
        }

        if (didChange) {
          this.lastConnectedHandlerId = this.handlerId;
          this.lastConnectedDragSource = dragSource;
          this.lastConnectedDragSourceOptions = this.dragSourceOptions;
          this.dragSourceUnsubscribe = this.backend.connectDragSource(this.handlerId, dragSource, this.dragSourceOptions);
        }
      }
    }, {
      key: "reconnectDragPreview",
      value: function reconnectDragPreview() {
        var dragPreview = this.dragPreview; // if nothing has changed then don't resubscribe

        var didChange = this.didHandlerIdChange() || this.didConnectedDragPreviewChange() || this.didDragPreviewOptionsChange();

        if (!this.handlerId) {
          this.disconnectDragPreview();
        } else if (this.dragPreview && didChange) {
          this.lastConnectedHandlerId = this.handlerId;
          this.lastConnectedDragPreview = dragPreview;
          this.lastConnectedDragPreviewOptions = this.dragPreviewOptions;
          this.disconnectDragPreview();
          this.dragPreviewUnsubscribe = this.backend.connectDragPreview(this.handlerId, dragPreview, this.dragPreviewOptions);
        }
      }
    }, {
      key: "didHandlerIdChange",
      value: function didHandlerIdChange() {
        return this.lastConnectedHandlerId !== this.handlerId;
      }
    }, {
      key: "didConnectedDragSourceChange",
      value: function didConnectedDragSourceChange() {
        return this.lastConnectedDragSource !== this.dragSource;
      }
    }, {
      key: "didConnectedDragPreviewChange",
      value: function didConnectedDragPreviewChange() {
        return this.lastConnectedDragPreview !== this.dragPreview;
      }
    }, {
      key: "didDragSourceOptionsChange",
      value: function didDragSourceOptionsChange() {
        return !shallowEqual(this.lastConnectedDragSourceOptions, this.dragSourceOptions);
      }
    }, {
      key: "didDragPreviewOptionsChange",
      value: function didDragPreviewOptionsChange() {
        return !shallowEqual(this.lastConnectedDragPreviewOptions, this.dragPreviewOptions);
      }
    }, {
      key: "disconnectDragSource",
      value: function disconnectDragSource() {
        if (this.dragSourceUnsubscribe) {
          this.dragSourceUnsubscribe();
          this.dragSourceUnsubscribe = undefined;
        }
      }
    }, {
      key: "disconnectDragPreview",
      value: function disconnectDragPreview() {
        if (this.dragPreviewUnsubscribe) {
          this.dragPreviewUnsubscribe();
          this.dragPreviewUnsubscribe = undefined;
          this.dragPreviewNode = null;
          this.dragPreviewRef = null;
        }
      }
    }, {
      key: "clearDragSource",
      value: function clearDragSource() {
        this.dragSourceNode = null;
        this.dragSourceRef = null;
      }
    }, {
      key: "clearDragPreview",
      value: function clearDragPreview() {
        this.dragPreviewNode = null;
        this.dragPreviewRef = null;
      }
    }, {
      key: "connectTarget",
      get: function get() {
        return this.dragSource;
      }
    }, {
      key: "dragSourceOptions",
      get: function get() {
        return this.dragSourceOptionsInternal;
      },
      set: function set(options) {
        this.dragSourceOptionsInternal = options;
      }
    }, {
      key: "dragPreviewOptions",
      get: function get() {
        return this.dragPreviewOptionsInternal;
      },
      set: function set(options) {
        this.dragPreviewOptionsInternal = options;
      }
    }, {
      key: "dragSource",
      get: function get() {
        return this.dragSourceNode || this.dragSourceRef && this.dragSourceRef.current;
      }
    }, {
      key: "dragPreview",
      get: function get() {
        return this.dragPreviewNode || this.dragPreviewRef && this.dragPreviewRef.current;
      }
    }]);

    return SourceConnector;
  }();

  function _slicedToArray$4(arr, i) { return _arrayWithHoles$4(arr) || _iterableToArrayLimit$4(arr, i) || _nonIterableRest$4(); }

  function _nonIterableRest$4() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$4(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$4(arr) { if (Array.isArray(arr)) return arr; }

  function _typeof$3(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$3 = function _typeof(obj) { return typeof obj; }; } else { _typeof$3 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$3(obj); }
  function useDragSourceMonitor() {
    var manager = useDragDropManager();
    var monitor = React.useMemo(function () {
      return new DragSourceMonitorImpl(manager);
    }, [manager]);
    var connector = React.useMemo(function () {
      return new SourceConnector(manager.getBackend());
    }, [manager]);
    return [monitor, connector];
  }
  function useDragHandler(spec, monitor, connector) {
    var manager = useDragDropManager();
    var handler = React.useMemo(function () {
      return {
        beginDrag: function beginDrag() {
          var _spec$current = spec.current,
              begin = _spec$current.begin,
              item = _spec$current.item;

          if (begin) {
            var beginResult = begin(monitor);
            invariant(beginResult == null || _typeof$3(beginResult) === 'object', 'dragSpec.begin() must either return an object, undefined, or null');
            return beginResult || item || {};
          }

          return item || {};
        },
        canDrag: function canDrag() {
          if (typeof spec.current.canDrag === 'boolean') {
            return spec.current.canDrag;
          } else if (typeof spec.current.canDrag === 'function') {
            return spec.current.canDrag(monitor);
          } else {
            return true;
          }
        },
        isDragging: function isDragging(globalMonitor, target) {
          var isDragging = spec.current.isDragging;
          return isDragging ? isDragging(monitor) : target === globalMonitor.getSourceId();
        },
        endDrag: function endDrag() {
          var end = spec.current.end;

          if (end) {
            end(monitor.getItem(), monitor);
          }

          connector.reconnect();
        }
      };
    }, []);
    useIsomorphicLayoutEffect(function registerHandler() {
      var _registerSource = registerSource(spec.current.item.type, handler, manager),
          _registerSource2 = _slicedToArray$4(_registerSource, 2),
          handlerId = _registerSource2[0],
          unregister = _registerSource2[1];

      monitor.receiveHandlerId(handlerId);
      connector.receiveHandlerId(handlerId);
      return unregister;
    }, []);
  }

  function _slicedToArray$5(arr, i) { return _arrayWithHoles$5(arr) || _iterableToArrayLimit$5(arr, i) || _nonIterableRest$5(); }

  function _nonIterableRest$5() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$5(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$5(arr) { if (Array.isArray(arr)) return arr; }
  /**
   * useDragSource hook
   * @param sourceSpec The drag source specification *
   */

  function useDrag(spec) {
    var specRef = React.useRef(spec);
    specRef.current = spec; // TODO: wire options into createSourceConnector

    invariant(spec.item != null, 'item must be defined');
    invariant(spec.item.type != null, 'item type must be defined');

    var _useDragSourceMonitor = useDragSourceMonitor(),
        _useDragSourceMonitor2 = _slicedToArray$5(_useDragSourceMonitor, 2),
        monitor = _useDragSourceMonitor2[0],
        connector = _useDragSourceMonitor2[1];

    useDragHandler(specRef, monitor, connector);
    var result = useMonitorOutput(monitor, specRef.current.collect || function () {
      return {};
    }, function () {
      return connector.reconnect();
    });
    var connectDragSource = React.useMemo(function () {
      return connector.hooks.dragSource();
    }, [connector]);
    var connectDragPreview = React.useMemo(function () {
      return connector.hooks.dragPreview();
    }, [connector]);
    useIsomorphicLayoutEffect(function () {
      connector.dragSourceOptions = specRef.current.options || null;
      connector.reconnect();
    }, [connector]);
    useIsomorphicLayoutEffect(function () {
      connector.dragPreviewOptions = specRef.current.previewOptions || null;
      connector.reconnect();
    }, [connector]);
    return [result, connectDragSource, connectDragPreview];
  }

  function _classCallCheck$5(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$5(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$5(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$5(Constructor.prototype, protoProps); if (staticProps) _defineProperties$5(Constructor, staticProps); return Constructor; }
  var TargetConnector =
  /*#__PURE__*/
  function () {
    function TargetConnector(backend) {
      var _this = this;

      _classCallCheck$5(this, TargetConnector);

      this.hooks = wrapConnectorHooks({
        dropTarget: function dropTarget(node, options) {
          _this.clearDropTarget();

          _this.dropTargetOptions = options;

          if (isRef(node)) {
            _this.dropTargetRef = node;
          } else {
            _this.dropTargetNode = node;
          }

          _this.reconnect();
        }
      });
      this.handlerId = null; // The drop target may either be attached via ref or connect function

      this.dropTargetRef = null;
      this.dropTargetOptionsInternal = null;
      this.lastConnectedHandlerId = null;
      this.lastConnectedDropTarget = null;
      this.lastConnectedDropTargetOptions = null;
      this.backend = backend;
    }

    _createClass$5(TargetConnector, [{
      key: "reconnect",
      value: function reconnect() {
        // if nothing has changed then don't resubscribe
        var didChange = this.didHandlerIdChange() || this.didDropTargetChange() || this.didOptionsChange();

        if (didChange) {
          this.disconnectDropTarget();
        }

        var dropTarget = this.dropTarget;

        if (!this.handlerId) {
          return;
        }

        if (!dropTarget) {
          this.lastConnectedDropTarget = dropTarget;
          return;
        }

        if (didChange) {
          this.lastConnectedHandlerId = this.handlerId;
          this.lastConnectedDropTarget = dropTarget;
          this.lastConnectedDropTargetOptions = this.dropTargetOptions;
          this.unsubscribeDropTarget = this.backend.connectDropTarget(this.handlerId, dropTarget, this.dropTargetOptions);
        }
      }
    }, {
      key: "receiveHandlerId",
      value: function receiveHandlerId(newHandlerId) {
        if (newHandlerId === this.handlerId) {
          return;
        }

        this.handlerId = newHandlerId;
        this.reconnect();
      }
    }, {
      key: "didHandlerIdChange",
      value: function didHandlerIdChange() {
        return this.lastConnectedHandlerId !== this.handlerId;
      }
    }, {
      key: "didDropTargetChange",
      value: function didDropTargetChange() {
        return this.lastConnectedDropTarget !== this.dropTarget;
      }
    }, {
      key: "didOptionsChange",
      value: function didOptionsChange() {
        return !shallowEqual(this.lastConnectedDropTargetOptions, this.dropTargetOptions);
      }
    }, {
      key: "disconnectDropTarget",
      value: function disconnectDropTarget() {
        if (this.unsubscribeDropTarget) {
          this.unsubscribeDropTarget();
          this.unsubscribeDropTarget = undefined;
        }
      }
    }, {
      key: "clearDropTarget",
      value: function clearDropTarget() {
        this.dropTargetRef = null;
        this.dropTargetNode = null;
      }
    }, {
      key: "connectTarget",
      get: function get() {
        return this.dropTarget;
      }
    }, {
      key: "dropTargetOptions",
      get: function get() {
        return this.dropTargetOptionsInternal;
      },
      set: function set(options) {
        this.dropTargetOptionsInternal = options;
      }
    }, {
      key: "dropTarget",
      get: function get() {
        return this.dropTargetNode || this.dropTargetRef && this.dropTargetRef.current;
      }
    }]);

    return TargetConnector;
  }();

  function _classCallCheck$6(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$6(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$6(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$6(Constructor.prototype, protoProps); if (staticProps) _defineProperties$6(Constructor, staticProps); return Constructor; }
  var isCallingCanDrop = false;
  var DropTargetMonitorImpl =
  /*#__PURE__*/
  function () {
    function DropTargetMonitorImpl(manager) {
      _classCallCheck$6(this, DropTargetMonitorImpl);

      this.targetId = null;
      this.internalMonitor = manager.getMonitor();
    }

    _createClass$6(DropTargetMonitorImpl, [{
      key: "receiveHandlerId",
      value: function receiveHandlerId(targetId) {
        this.targetId = targetId;
      }
    }, {
      key: "getHandlerId",
      value: function getHandlerId() {
        return this.targetId;
      }
    }, {
      key: "subscribeToStateChange",
      value: function subscribeToStateChange(listener, options) {
        return this.internalMonitor.subscribeToStateChange(listener, options);
      }
    }, {
      key: "canDrop",
      value: function canDrop() {
        // Cut out early if the target id has not been set. This should prevent errors
        // where the user has an older version of dnd-core like in
        // https://github.com/react-dnd/react-dnd/issues/1310
        if (!this.targetId) {
          return false;
        }

        invariant(!isCallingCanDrop, 'You may not call monitor.canDrop() inside your canDrop() implementation. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target-monitor');

        try {
          isCallingCanDrop = true;
          return this.internalMonitor.canDropOnTarget(this.targetId);
        } finally {
          isCallingCanDrop = false;
        }
      }
    }, {
      key: "isOver",
      value: function isOver(options) {
        if (!this.targetId) {
          return false;
        }

        return this.internalMonitor.isOverTarget(this.targetId, options);
      }
    }, {
      key: "getItemType",
      value: function getItemType() {
        return this.internalMonitor.getItemType();
      }
    }, {
      key: "getItem",
      value: function getItem() {
        return this.internalMonitor.getItem();
      }
    }, {
      key: "getDropResult",
      value: function getDropResult() {
        return this.internalMonitor.getDropResult();
      }
    }, {
      key: "didDrop",
      value: function didDrop() {
        return this.internalMonitor.didDrop();
      }
    }, {
      key: "getInitialClientOffset",
      value: function getInitialClientOffset() {
        return this.internalMonitor.getInitialClientOffset();
      }
    }, {
      key: "getInitialSourceClientOffset",
      value: function getInitialSourceClientOffset() {
        return this.internalMonitor.getInitialSourceClientOffset();
      }
    }, {
      key: "getSourceClientOffset",
      value: function getSourceClientOffset() {
        return this.internalMonitor.getSourceClientOffset();
      }
    }, {
      key: "getClientOffset",
      value: function getClientOffset() {
        return this.internalMonitor.getClientOffset();
      }
    }, {
      key: "getDifferenceFromInitialOffset",
      value: function getDifferenceFromInitialOffset() {
        return this.internalMonitor.getDifferenceFromInitialOffset();
      }
    }]);

    return DropTargetMonitorImpl;
  }();

  function _slicedToArray$6(arr, i) { return _arrayWithHoles$6(arr) || _iterableToArrayLimit$6(arr, i) || _nonIterableRest$6(); }

  function _nonIterableRest$6() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$6(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$6(arr) { if (Array.isArray(arr)) return arr; }
  function useDropTargetMonitor() {
    var manager = useDragDropManager();
    var monitor = React.useMemo(function () {
      return new DropTargetMonitorImpl(manager);
    }, [manager]);
    var connector = React.useMemo(function () {
      return new TargetConnector(manager.getBackend());
    }, [manager]);
    return [monitor, connector];
  }
  function useDropHandler(spec, monitor, connector) {
    var manager = useDragDropManager();
    var handler = React.useMemo(function () {
      return {
        canDrop: function canDrop() {
          var canDrop = spec.current.canDrop;
          return canDrop ? canDrop(monitor.getItem(), monitor) : true;
        },
        hover: function hover() {
          var hover = spec.current.hover;

          if (hover) {
            hover(monitor.getItem(), monitor);
          }
        },
        drop: function drop() {
          var drop = spec.current.drop;

          if (drop) {
            return drop(monitor.getItem(), monitor);
          }
        }
      };
    }, [monitor]);
    useIsomorphicLayoutEffect(function registerHandler() {
      var _registerTarget = registerTarget(spec.current.accept, handler, manager),
          _registerTarget2 = _slicedToArray$6(_registerTarget, 2),
          handlerId = _registerTarget2[0],
          unregister = _registerTarget2[1];

      monitor.receiveHandlerId(handlerId);
      connector.receiveHandlerId(handlerId);
      return unregister;
    }, [monitor, connector]);
  }

  function _slicedToArray$7(arr, i) { return _arrayWithHoles$7(arr) || _iterableToArrayLimit$7(arr, i) || _nonIterableRest$7(); }

  function _nonIterableRest$7() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$7(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$7(arr) { if (Array.isArray(arr)) return arr; }
  /**
   * useDropTarget Hook
   * @param spec The drop target specification
   */

  function useDrop(spec) {
    var specRef = React.useRef(spec);
    specRef.current = spec;
    invariant(spec.accept != null, 'accept must be defined');

    var _useDropTargetMonitor = useDropTargetMonitor(),
        _useDropTargetMonitor2 = _slicedToArray$7(_useDropTargetMonitor, 2),
        monitor = _useDropTargetMonitor2[0],
        connector = _useDropTargetMonitor2[1];

    useDropHandler(specRef, monitor, connector);
    var result = useMonitorOutput(monitor, specRef.current.collect || function () {
      return {};
    }, function () {
      return connector.reconnect();
    });
    var connectDropTarget = React.useMemo(function () {
      return connector.hooks.dropTarget();
    }, [connector]);
    useIsomorphicLayoutEffect(function () {
      connector.dropTargetOptions = spec.options || null;
      connector.reconnect();
    }, [spec.options]);
    return [result, connectDropTarget];
  }

  function _slicedToArray$8(arr, i) { return _arrayWithHoles$8(arr) || _iterableToArrayLimit$8(arr, i) || _nonIterableRest$8(); }

  function _nonIterableRest$8() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$8(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$8(arr) { if (Array.isArray(arr)) return arr; }
  /**
   * useDragLayer Hook
   * @param collector The property collector
   */

  function useDragLayer(collect) {
    var dragDropManager = useDragDropManager();
    var monitor = dragDropManager.getMonitor();

    var _useCollector = useCollector(monitor, collect),
        _useCollector2 = _slicedToArray$8(_useCollector, 2),
        collected = _useCollector2[0],
        updateCollected = _useCollector2[1];

    React.useEffect(function () {
      return monitor.subscribeToOffsetChange(updateCollected);
    });
    React.useEffect(function () {
      return monitor.subscribeToStateChange(updateCollected);
    });
    return collected;
  }

  function _typeof$4(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$4 = function _typeof(obj) { return typeof obj; }; } else { _typeof$4 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$4(obj); }

  // cheap lodash replacements
  function isFunction(input) {
    return typeof input === 'function';
  }
  function noop() {// noop
  }

  function isObjectLike(input) {
    return _typeof$4(input) === 'object' && input !== null;
  }

  function isPlainObject$1(input) {
    if (!isObjectLike(input)) {
      return false;
    }

    if (Object.getPrototypeOf(input) === null) {
      return true;
    }

    var proto = input;

    while (Object.getPrototypeOf(proto) !== null) {
      proto = Object.getPrototypeOf(proto);
    }

    return Object.getPrototypeOf(input) === proto;
  }

  function getDecoratedComponent(instanceRef) {
    var currentRef = instanceRef.current;

    if (currentRef == null) {
      return null;
    } else if (currentRef.decoratedRef) {
      // go through the private field in decorateHandler to avoid the invariant hit
      return currentRef.decoratedRef.current;
    } else {
      return currentRef;
    }
  }
  function isClassComponent(Component) {
    return Component && Component.prototype && typeof Component.prototype.render === 'function';
  }
  function isRefForwardingComponent(C) {
    return C && C.$$typeof && C.$$typeof.toString() === 'Symbol(react.forward_ref)';
  }
  function isRefable(C) {
    return isClassComponent(C) || isRefForwardingComponent(C);
  }
  function checkDecoratorArguments(functionName, signature) {
    if ("development" !== 'production') {
      for (var i = 0; i < (arguments.length <= 2 ? 0 : arguments.length - 2); i++) {
        var arg = i + 2 < 2 || arguments.length <= i + 2 ? undefined : arguments[i + 2];

        if (arg && arg.prototype && arg.prototype.render) {
          // eslint-disable-next-line no-console
          console.error('You seem to be applying the arguments in the wrong order. ' + "It should be ".concat(functionName, "(").concat(signature, ")(Component), not the other way around. ") + 'Read more: http://react-dnd.github.io/react-dnd/docs/troubleshooting#you-seem-to-be-applying-the-arguments-in-the-wrong-order');
          return;
        }
      }
    }
  }

  function unwrapExports (x) {
  	return x && x.__esModule && Object.prototype.hasOwnProperty.call(x, 'default') ? x['default'] : x;
  }

  function createCommonjsModule(fn, module) {
  	return module = { exports: {} }, fn(module, module.exports), module.exports;
  }

  var reactIs_production_min = createCommonjsModule(function (module, exports) {
  Object.defineProperty(exports,"__esModule",{value:!0});
  var b="function"===typeof Symbol&&Symbol.for,c=b?Symbol.for("react.element"):60103,d=b?Symbol.for("react.portal"):60106,e=b?Symbol.for("react.fragment"):60107,f=b?Symbol.for("react.strict_mode"):60108,g=b?Symbol.for("react.profiler"):60114,h=b?Symbol.for("react.provider"):60109,k=b?Symbol.for("react.context"):60110,l=b?Symbol.for("react.async_mode"):60111,m=b?Symbol.for("react.concurrent_mode"):60111,n=b?Symbol.for("react.forward_ref"):60112,p=b?Symbol.for("react.suspense"):60113,q=b?Symbol.for("react.suspense_list"):
  60120,r=b?Symbol.for("react.memo"):60115,t=b?Symbol.for("react.lazy"):60116,v=b?Symbol.for("react.fundamental"):60117,w=b?Symbol.for("react.responder"):60118,x=b?Symbol.for("react.scope"):60119;function y(a){if("object"===typeof a&&null!==a){var u=a.$$typeof;switch(u){case c:switch(a=a.type,a){case l:case m:case e:case g:case f:case p:return a;default:switch(a=a&&a.$$typeof,a){case k:case n:case t:case r:case h:return a;default:return u}}case d:return u}}}function z(a){return y(a)===m}
  exports.typeOf=y;exports.AsyncMode=l;exports.ConcurrentMode=m;exports.ContextConsumer=k;exports.ContextProvider=h;exports.Element=c;exports.ForwardRef=n;exports.Fragment=e;exports.Lazy=t;exports.Memo=r;exports.Portal=d;exports.Profiler=g;exports.StrictMode=f;exports.Suspense=p;
  exports.isValidElementType=function(a){return "string"===typeof a||"function"===typeof a||a===e||a===m||a===g||a===f||a===p||a===q||"object"===typeof a&&null!==a&&(a.$$typeof===t||a.$$typeof===r||a.$$typeof===h||a.$$typeof===k||a.$$typeof===n||a.$$typeof===v||a.$$typeof===w||a.$$typeof===x)};exports.isAsyncMode=function(a){return z(a)||y(a)===l};exports.isConcurrentMode=z;exports.isContextConsumer=function(a){return y(a)===k};exports.isContextProvider=function(a){return y(a)===h};
  exports.isElement=function(a){return "object"===typeof a&&null!==a&&a.$$typeof===c};exports.isForwardRef=function(a){return y(a)===n};exports.isFragment=function(a){return y(a)===e};exports.isLazy=function(a){return y(a)===t};exports.isMemo=function(a){return y(a)===r};exports.isPortal=function(a){return y(a)===d};exports.isProfiler=function(a){return y(a)===g};exports.isStrictMode=function(a){return y(a)===f};exports.isSuspense=function(a){return y(a)===p};
  });

  unwrapExports(reactIs_production_min);
  var reactIs_production_min_1 = reactIs_production_min.typeOf;
  var reactIs_production_min_2 = reactIs_production_min.AsyncMode;
  var reactIs_production_min_3 = reactIs_production_min.ConcurrentMode;
  var reactIs_production_min_4 = reactIs_production_min.ContextConsumer;
  var reactIs_production_min_5 = reactIs_production_min.ContextProvider;
  var reactIs_production_min_6 = reactIs_production_min.Element;
  var reactIs_production_min_7 = reactIs_production_min.ForwardRef;
  var reactIs_production_min_8 = reactIs_production_min.Fragment;
  var reactIs_production_min_9 = reactIs_production_min.Lazy;
  var reactIs_production_min_10 = reactIs_production_min.Memo;
  var reactIs_production_min_11 = reactIs_production_min.Portal;
  var reactIs_production_min_12 = reactIs_production_min.Profiler;
  var reactIs_production_min_13 = reactIs_production_min.StrictMode;
  var reactIs_production_min_14 = reactIs_production_min.Suspense;
  var reactIs_production_min_15 = reactIs_production_min.isValidElementType;
  var reactIs_production_min_16 = reactIs_production_min.isAsyncMode;
  var reactIs_production_min_17 = reactIs_production_min.isConcurrentMode;
  var reactIs_production_min_18 = reactIs_production_min.isContextConsumer;
  var reactIs_production_min_19 = reactIs_production_min.isContextProvider;
  var reactIs_production_min_20 = reactIs_production_min.isElement;
  var reactIs_production_min_21 = reactIs_production_min.isForwardRef;
  var reactIs_production_min_22 = reactIs_production_min.isFragment;
  var reactIs_production_min_23 = reactIs_production_min.isLazy;
  var reactIs_production_min_24 = reactIs_production_min.isMemo;
  var reactIs_production_min_25 = reactIs_production_min.isPortal;
  var reactIs_production_min_26 = reactIs_production_min.isProfiler;
  var reactIs_production_min_27 = reactIs_production_min.isStrictMode;
  var reactIs_production_min_28 = reactIs_production_min.isSuspense;

  var reactIs_development = createCommonjsModule(function (module, exports) {



  if ("development" !== "production") {
    (function() {

  Object.defineProperty(exports, '__esModule', { value: true });

  // The Symbol used to tag the ReactElement-like types. If there is no native Symbol
  // nor polyfill, then a plain number is used for performance.
  var hasSymbol = typeof Symbol === 'function' && Symbol.for;
  var REACT_ELEMENT_TYPE = hasSymbol ? Symbol.for('react.element') : 0xeac7;
  var REACT_PORTAL_TYPE = hasSymbol ? Symbol.for('react.portal') : 0xeaca;
  var REACT_FRAGMENT_TYPE = hasSymbol ? Symbol.for('react.fragment') : 0xeacb;
  var REACT_STRICT_MODE_TYPE = hasSymbol ? Symbol.for('react.strict_mode') : 0xeacc;
  var REACT_PROFILER_TYPE = hasSymbol ? Symbol.for('react.profiler') : 0xead2;
  var REACT_PROVIDER_TYPE = hasSymbol ? Symbol.for('react.provider') : 0xeacd;
  var REACT_CONTEXT_TYPE = hasSymbol ? Symbol.for('react.context') : 0xeace; // TODO: We don't use AsyncMode or ConcurrentMode anymore. They were temporary
  // (unstable) APIs that have been removed. Can we remove the symbols?

  var REACT_ASYNC_MODE_TYPE = hasSymbol ? Symbol.for('react.async_mode') : 0xeacf;
  var REACT_CONCURRENT_MODE_TYPE = hasSymbol ? Symbol.for('react.concurrent_mode') : 0xeacf;
  var REACT_FORWARD_REF_TYPE = hasSymbol ? Symbol.for('react.forward_ref') : 0xead0;
  var REACT_SUSPENSE_TYPE = hasSymbol ? Symbol.for('react.suspense') : 0xead1;
  var REACT_SUSPENSE_LIST_TYPE = hasSymbol ? Symbol.for('react.suspense_list') : 0xead8;
  var REACT_MEMO_TYPE = hasSymbol ? Symbol.for('react.memo') : 0xead3;
  var REACT_LAZY_TYPE = hasSymbol ? Symbol.for('react.lazy') : 0xead4;
  var REACT_FUNDAMENTAL_TYPE = hasSymbol ? Symbol.for('react.fundamental') : 0xead5;
  var REACT_RESPONDER_TYPE = hasSymbol ? Symbol.for('react.responder') : 0xead6;
  var REACT_SCOPE_TYPE = hasSymbol ? Symbol.for('react.scope') : 0xead7;

  function isValidElementType(type) {
    return typeof type === 'string' || typeof type === 'function' || // Note: its typeof might be other than 'symbol' or 'number' if it's a polyfill.
    type === REACT_FRAGMENT_TYPE || type === REACT_CONCURRENT_MODE_TYPE || type === REACT_PROFILER_TYPE || type === REACT_STRICT_MODE_TYPE || type === REACT_SUSPENSE_TYPE || type === REACT_SUSPENSE_LIST_TYPE || typeof type === 'object' && type !== null && (type.$$typeof === REACT_LAZY_TYPE || type.$$typeof === REACT_MEMO_TYPE || type.$$typeof === REACT_PROVIDER_TYPE || type.$$typeof === REACT_CONTEXT_TYPE || type.$$typeof === REACT_FORWARD_REF_TYPE || type.$$typeof === REACT_FUNDAMENTAL_TYPE || type.$$typeof === REACT_RESPONDER_TYPE || type.$$typeof === REACT_SCOPE_TYPE);
  }

  /**
   * Forked from fbjs/warning:
   * https://github.com/facebook/fbjs/blob/e66ba20ad5be433eb54423f2b097d829324d9de6/packages/fbjs/src/__forks__/warning.js
   *
   * Only change is we use console.warn instead of console.error,
   * and do nothing when 'console' is not supported.
   * This really simplifies the code.
   * ---
   * Similar to invariant but only logs a warning if the condition is not met.
   * This can be used to log issues in development environments in critical
   * paths. Removing the logging code for production environments will keep the
   * same logic and follow the same code paths.
   */
  var lowPriorityWarningWithoutStack = function () {};

  {
    var printWarning = function (format) {
      for (var _len = arguments.length, args = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
        args[_key - 1] = arguments[_key];
      }

      var argIndex = 0;
      var message = 'Warning: ' + format.replace(/%s/g, function () {
        return args[argIndex++];
      });

      if (typeof console !== 'undefined') {
        console.warn(message);
      }

      try {
        // --- Welcome to debugging React ---
        // This error was thrown as a convenience so that you can use this stack
        // to find the callsite that caused this warning to fire.
        throw new Error(message);
      } catch (x) {}
    };

    lowPriorityWarningWithoutStack = function (condition, format) {
      if (format === undefined) {
        throw new Error('`lowPriorityWarningWithoutStack(condition, format, ...args)` requires a warning ' + 'message argument');
      }

      if (!condition) {
        for (var _len2 = arguments.length, args = new Array(_len2 > 2 ? _len2 - 2 : 0), _key2 = 2; _key2 < _len2; _key2++) {
          args[_key2 - 2] = arguments[_key2];
        }

        printWarning.apply(void 0, [format].concat(args));
      }
    };
  }

  var lowPriorityWarningWithoutStack$1 = lowPriorityWarningWithoutStack;

  function typeOf(object) {
    if (typeof object === 'object' && object !== null) {
      var $$typeof = object.$$typeof;

      switch ($$typeof) {
        case REACT_ELEMENT_TYPE:
          var type = object.type;

          switch (type) {
            case REACT_ASYNC_MODE_TYPE:
            case REACT_CONCURRENT_MODE_TYPE:
            case REACT_FRAGMENT_TYPE:
            case REACT_PROFILER_TYPE:
            case REACT_STRICT_MODE_TYPE:
            case REACT_SUSPENSE_TYPE:
              return type;

            default:
              var $$typeofType = type && type.$$typeof;

              switch ($$typeofType) {
                case REACT_CONTEXT_TYPE:
                case REACT_FORWARD_REF_TYPE:
                case REACT_LAZY_TYPE:
                case REACT_MEMO_TYPE:
                case REACT_PROVIDER_TYPE:
                  return $$typeofType;

                default:
                  return $$typeof;
              }

          }

        case REACT_PORTAL_TYPE:
          return $$typeof;
      }
    }

    return undefined;
  } // AsyncMode is deprecated along with isAsyncMode

  var AsyncMode = REACT_ASYNC_MODE_TYPE;
  var ConcurrentMode = REACT_CONCURRENT_MODE_TYPE;
  var ContextConsumer = REACT_CONTEXT_TYPE;
  var ContextProvider = REACT_PROVIDER_TYPE;
  var Element = REACT_ELEMENT_TYPE;
  var ForwardRef = REACT_FORWARD_REF_TYPE;
  var Fragment = REACT_FRAGMENT_TYPE;
  var Lazy = REACT_LAZY_TYPE;
  var Memo = REACT_MEMO_TYPE;
  var Portal = REACT_PORTAL_TYPE;
  var Profiler = REACT_PROFILER_TYPE;
  var StrictMode = REACT_STRICT_MODE_TYPE;
  var Suspense = REACT_SUSPENSE_TYPE;
  var hasWarnedAboutDeprecatedIsAsyncMode = false; // AsyncMode should be deprecated

  function isAsyncMode(object) {
    {
      if (!hasWarnedAboutDeprecatedIsAsyncMode) {
        hasWarnedAboutDeprecatedIsAsyncMode = true;
        lowPriorityWarningWithoutStack$1(false, 'The ReactIs.isAsyncMode() alias has been deprecated, ' + 'and will be removed in React 17+. Update your code to use ' + 'ReactIs.isConcurrentMode() instead. It has the exact same API.');
      }
    }

    return isConcurrentMode(object) || typeOf(object) === REACT_ASYNC_MODE_TYPE;
  }
  function isConcurrentMode(object) {
    return typeOf(object) === REACT_CONCURRENT_MODE_TYPE;
  }
  function isContextConsumer(object) {
    return typeOf(object) === REACT_CONTEXT_TYPE;
  }
  function isContextProvider(object) {
    return typeOf(object) === REACT_PROVIDER_TYPE;
  }
  function isElement(object) {
    return typeof object === 'object' && object !== null && object.$$typeof === REACT_ELEMENT_TYPE;
  }
  function isForwardRef(object) {
    return typeOf(object) === REACT_FORWARD_REF_TYPE;
  }
  function isFragment(object) {
    return typeOf(object) === REACT_FRAGMENT_TYPE;
  }
  function isLazy(object) {
    return typeOf(object) === REACT_LAZY_TYPE;
  }
  function isMemo(object) {
    return typeOf(object) === REACT_MEMO_TYPE;
  }
  function isPortal(object) {
    return typeOf(object) === REACT_PORTAL_TYPE;
  }
  function isProfiler(object) {
    return typeOf(object) === REACT_PROFILER_TYPE;
  }
  function isStrictMode(object) {
    return typeOf(object) === REACT_STRICT_MODE_TYPE;
  }
  function isSuspense(object) {
    return typeOf(object) === REACT_SUSPENSE_TYPE;
  }

  exports.typeOf = typeOf;
  exports.AsyncMode = AsyncMode;
  exports.ConcurrentMode = ConcurrentMode;
  exports.ContextConsumer = ContextConsumer;
  exports.ContextProvider = ContextProvider;
  exports.Element = Element;
  exports.ForwardRef = ForwardRef;
  exports.Fragment = Fragment;
  exports.Lazy = Lazy;
  exports.Memo = Memo;
  exports.Portal = Portal;
  exports.Profiler = Profiler;
  exports.StrictMode = StrictMode;
  exports.Suspense = Suspense;
  exports.isValidElementType = isValidElementType;
  exports.isAsyncMode = isAsyncMode;
  exports.isConcurrentMode = isConcurrentMode;
  exports.isContextConsumer = isContextConsumer;
  exports.isContextProvider = isContextProvider;
  exports.isElement = isElement;
  exports.isForwardRef = isForwardRef;
  exports.isFragment = isFragment;
  exports.isLazy = isLazy;
  exports.isMemo = isMemo;
  exports.isPortal = isPortal;
  exports.isProfiler = isProfiler;
  exports.isStrictMode = isStrictMode;
  exports.isSuspense = isSuspense;
    })();
  }
  });

  unwrapExports(reactIs_development);
  var reactIs_development_1 = reactIs_development.typeOf;
  var reactIs_development_2 = reactIs_development.AsyncMode;
  var reactIs_development_3 = reactIs_development.ConcurrentMode;
  var reactIs_development_4 = reactIs_development.ContextConsumer;
  var reactIs_development_5 = reactIs_development.ContextProvider;
  var reactIs_development_6 = reactIs_development.Element;
  var reactIs_development_7 = reactIs_development.ForwardRef;
  var reactIs_development_8 = reactIs_development.Fragment;
  var reactIs_development_9 = reactIs_development.Lazy;
  var reactIs_development_10 = reactIs_development.Memo;
  var reactIs_development_11 = reactIs_development.Portal;
  var reactIs_development_12 = reactIs_development.Profiler;
  var reactIs_development_13 = reactIs_development.StrictMode;
  var reactIs_development_14 = reactIs_development.Suspense;
  var reactIs_development_15 = reactIs_development.isValidElementType;
  var reactIs_development_16 = reactIs_development.isAsyncMode;
  var reactIs_development_17 = reactIs_development.isConcurrentMode;
  var reactIs_development_18 = reactIs_development.isContextConsumer;
  var reactIs_development_19 = reactIs_development.isContextProvider;
  var reactIs_development_20 = reactIs_development.isElement;
  var reactIs_development_21 = reactIs_development.isForwardRef;
  var reactIs_development_22 = reactIs_development.isFragment;
  var reactIs_development_23 = reactIs_development.isLazy;
  var reactIs_development_24 = reactIs_development.isMemo;
  var reactIs_development_25 = reactIs_development.isPortal;
  var reactIs_development_26 = reactIs_development.isProfiler;
  var reactIs_development_27 = reactIs_development.isStrictMode;
  var reactIs_development_28 = reactIs_development.isSuspense;

  var reactIs = createCommonjsModule(function (module) {

  if ("development" === 'production') {
    module.exports = reactIs_production_min;
  } else {
    module.exports = reactIs_development;
  }
  });

  /**
   * Copyright 2015, Yahoo! Inc.
   * Copyrights licensed under the New BSD License. See the accompanying LICENSE file for terms.
   */
  var REACT_STATICS = {
    childContextTypes: true,
    contextType: true,
    contextTypes: true,
    defaultProps: true,
    displayName: true,
    getDefaultProps: true,
    getDerivedStateFromError: true,
    getDerivedStateFromProps: true,
    mixins: true,
    propTypes: true,
    type: true
  };
  var KNOWN_STATICS = {
    name: true,
    length: true,
    prototype: true,
    caller: true,
    callee: true,
    arguments: true,
    arity: true
  };
  var FORWARD_REF_STATICS = {
    '$$typeof': true,
    render: true,
    defaultProps: true,
    displayName: true,
    propTypes: true
  };
  var MEMO_STATICS = {
    '$$typeof': true,
    compare: true,
    defaultProps: true,
    displayName: true,
    propTypes: true,
    type: true
  };
  var TYPE_STATICS = {};
  TYPE_STATICS[reactIs.ForwardRef] = FORWARD_REF_STATICS;

  function getStatics(component) {
    if (reactIs.isMemo(component)) {
      return MEMO_STATICS;
    }

    return TYPE_STATICS[component['$$typeof']] || REACT_STATICS;
  }

  var defineProperty = Object.defineProperty;
  var getOwnPropertyNames = Object.getOwnPropertyNames;
  var getOwnPropertySymbols = Object.getOwnPropertySymbols;
  var getOwnPropertyDescriptor = Object.getOwnPropertyDescriptor;
  var getPrototypeOf = Object.getPrototypeOf;
  var objectPrototype = Object.prototype;
  function hoistNonReactStatics(targetComponent, sourceComponent, blacklist) {
    if (typeof sourceComponent !== 'string') {
      // don't hoist over string (html) components
      if (objectPrototype) {
        var inheritedComponent = getPrototypeOf(sourceComponent);

        if (inheritedComponent && inheritedComponent !== objectPrototype) {
          hoistNonReactStatics(targetComponent, inheritedComponent, blacklist);
        }
      }

      var keys = getOwnPropertyNames(sourceComponent);

      if (getOwnPropertySymbols) {
        keys = keys.concat(getOwnPropertySymbols(sourceComponent));
      }

      var targetStatics = getStatics(targetComponent);
      var sourceStatics = getStatics(sourceComponent);

      for (var i = 0; i < keys.length; ++i) {
        var key = keys[i];

        if (!KNOWN_STATICS[key] && !(blacklist && blacklist[key]) && !(sourceStatics && sourceStatics[key]) && !(targetStatics && targetStatics[key])) {
          var descriptor = getOwnPropertyDescriptor(sourceComponent, key);

          try {
            // Avoid failures from read-only properties
            defineProperty(targetComponent, key, descriptor);
          } catch (e) {}
        }
      }
    }

    return targetComponent;
  }

  var hoistNonReactStatics_cjs = hoistNonReactStatics;

  function _classCallCheck$7(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$7(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$7(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$7(Constructor.prototype, protoProps); if (staticProps) _defineProperties$7(Constructor, staticProps); return Constructor; }
  /**
   * Provides a set of static methods for creating Disposables.
   * @param {Function} action Action to run during the first call to dispose.
   * The action is guaranteed to be run at most once.
   */

  var Disposable =
  /*#__PURE__*/
  function () {
    function Disposable(action) {
      _classCallCheck$7(this, Disposable);

      this.isDisposed = false;
      this.action = isFunction(action) ? action : noop;
    }
    /**
     * Validates whether the given object is a disposable
     * @param {Object} Object to test whether it has a dispose method
     * @returns {Boolean} true if a disposable object, else false.
     */


    _createClass$7(Disposable, [{
      key: "dispose",

      /** Performs the task of cleaning up resources. */
      value: function dispose() {
        if (!this.isDisposed) {
          this.action();
          this.isDisposed = true;
        }
      }
    }], [{
      key: "isDisposable",
      value: function isDisposable(d) {
        return d && isFunction(d.dispose);
      }
    }, {
      key: "_fixup",
      value: function _fixup(result) {
        return Disposable.isDisposable(result) ? result : Disposable.empty;
      }
      /**
       * Creates a disposable object that invokes the specified action when disposed.
       * @param {Function} dispose Action to run during the first call to dispose.
       * The action is guaranteed to be run at most once.
       * @return {Disposable} The disposable object that runs the given action upon disposal.
       */

    }, {
      key: "create",
      value: function create(action) {
        return new Disposable(action);
      }
    }]);

    return Disposable;
  }();
  /**
   * Gets the disposable that does nothing when disposed.
   */

  Disposable.empty = {
    dispose: noop
  };
  /**
   * Represents a group of disposable resources that are disposed together.
   * @constructor
   */

  var CompositeDisposable =
  /*#__PURE__*/
  function () {
    function CompositeDisposable() {
      _classCallCheck$7(this, CompositeDisposable);

      this.isDisposed = false;

      for (var _len = arguments.length, disposables = new Array(_len), _key = 0; _key < _len; _key++) {
        disposables[_key] = arguments[_key];
      }

      this.disposables = disposables;
    }
    /**
     * Adds a disposable to the CompositeDisposable or disposes the disposable if the CompositeDisposable is disposed.
     * @param {Any} item Disposable to add.
     */


    _createClass$7(CompositeDisposable, [{
      key: "add",
      value: function add(item) {
        if (this.isDisposed) {
          item.dispose();
        } else {
          this.disposables.push(item);
        }
      }
      /**
       * Removes and disposes the first occurrence of a disposable from the CompositeDisposable.
       * @param {Any} item Disposable to remove.
       * @returns {Boolean} true if found; false otherwise.
       */

    }, {
      key: "remove",
      value: function remove(item) {
        var shouldDispose = false;

        if (!this.isDisposed) {
          var idx = this.disposables.indexOf(item);

          if (idx !== -1) {
            shouldDispose = true;
            this.disposables.splice(idx, 1);
            item.dispose();
          }
        }

        return shouldDispose;
      }
      /**
       *  Disposes all disposables in the group and removes them from the group but
       *  does not dispose the CompositeDisposable.
       */

    }, {
      key: "clear",
      value: function clear() {
        if (!this.isDisposed) {
          var len = this.disposables.length;
          var currentDisposables = new Array(len);

          for (var i = 0; i < len; i++) {
            currentDisposables[i] = this.disposables[i];
          }

          this.disposables = [];

          for (var _i = 0; _i < len; _i++) {
            currentDisposables[_i].dispose();
          }
        }
      }
      /**
       *  Disposes all disposables in the group and removes them from the group.
       */

    }, {
      key: "dispose",
      value: function dispose() {
        if (!this.isDisposed) {
          this.isDisposed = true;
          var len = this.disposables.length;
          var currentDisposables = new Array(len);

          for (var i = 0; i < len; i++) {
            currentDisposables[i] = this.disposables[i];
          }

          this.disposables = [];

          for (var _i2 = 0; _i2 < len; _i2++) {
            currentDisposables[_i2].dispose();
          }
        }
      }
    }]);

    return CompositeDisposable;
  }();
  /**
   * Represents a disposable resource whose underlying disposable resource can
   * be replaced by another disposable resource, causing automatic disposal of
   * the previous underlying disposable resource.
   */

  var SerialDisposable =
  /*#__PURE__*/
  function () {
    function SerialDisposable() {
      _classCallCheck$7(this, SerialDisposable);

      this.isDisposed = false;
    }
    /**
     * Gets the underlying disposable.
     * @returns {Any} the underlying disposable.
     */


    _createClass$7(SerialDisposable, [{
      key: "getDisposable",
      value: function getDisposable() {
        return this.current;
      }
    }, {
      key: "setDisposable",
      value: function setDisposable(value) {
        var shouldDispose = this.isDisposed;

        if (!shouldDispose) {
          var old = this.current;
          this.current = value;

          if (old) {
            old.dispose();
          }
        }

        if (shouldDispose && value) {
          value.dispose();
        }
      }
      /** Performs the task of cleaning up resources. */

    }, {
      key: "dispose",
      value: function dispose() {
        if (!this.isDisposed) {
          this.isDisposed = true;
          var old = this.current;
          this.current = undefined;

          if (old) {
            old.dispose();
          }
        }
      }
    }]);

    return SerialDisposable;
  }();

  function _typeof$5(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$5 = function _typeof(obj) { return typeof obj; }; } else { _typeof$5 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$5(obj); }

  function _slicedToArray$9(arr, i) { return _arrayWithHoles$9(arr) || _iterableToArrayLimit$9(arr, i) || _nonIterableRest$9(); }

  function _nonIterableRest$9() { throw new TypeError("Invalid attempt to destructure non-iterable instance"); }

  function _iterableToArrayLimit$9(arr, i) { if (!(Symbol.iterator in Object(arr) || Object.prototype.toString.call(arr) === "[object Arguments]")) { return; } var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arr[Symbol.iterator](), _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i["return"] != null) _i["return"](); } finally { if (_d) throw _e; } } return _arr; }

  function _arrayWithHoles$9(arr) { if (Array.isArray(arr)) return arr; }

  function _classCallCheck$8(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$8(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$8(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$8(Constructor.prototype, protoProps); if (staticProps) _defineProperties$8(Constructor, staticProps); return Constructor; }

  function _possibleConstructorReturn(self, call) { if (call && (_typeof$5(call) === "object" || typeof call === "function")) { return call; } return _assertThisInitialized(self); }

  function _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }

  function _getPrototypeOf(o) { _getPrototypeOf = Object.setPrototypeOf ? Object.getPrototypeOf : function _getPrototypeOf(o) { return o.__proto__ || Object.getPrototypeOf(o); }; return _getPrototypeOf(o); }

  function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, writable: true, configurable: true } }); if (superClass) _setPrototypeOf(subClass, superClass); }

  function _setPrototypeOf(o, p) { _setPrototypeOf = Object.setPrototypeOf || function _setPrototypeOf(o, p) { o.__proto__ = p; return o; }; return _setPrototypeOf(o, p); }
  function decorateHandler(_ref) {
    var DecoratedComponent = _ref.DecoratedComponent,
        createHandler = _ref.createHandler,
        createMonitor = _ref.createMonitor,
        createConnector = _ref.createConnector,
        registerHandler = _ref.registerHandler,
        containerDisplayName = _ref.containerDisplayName,
        getType = _ref.getType,
        collect = _ref.collect,
        options = _ref.options;
    var _options$arePropsEqua = options.arePropsEqual,
        arePropsEqual = _options$arePropsEqua === void 0 ? shallowEqual : _options$arePropsEqua;
    var Decorated = DecoratedComponent;
    var displayName = DecoratedComponent.displayName || DecoratedComponent.name || 'Component';

    var DragDropContainer =
    /*#__PURE__*/
    function (_React$Component) {
      _inherits(DragDropContainer, _React$Component);

      function DragDropContainer(props) {
        var _this;

        _classCallCheck$8(this, DragDropContainer);

        _this = _possibleConstructorReturn(this, _getPrototypeOf(DragDropContainer).call(this, props));
        _this.decoratedRef = React.createRef();

        _this.handleChange = function () {
          var nextState = _this.getCurrentState();

          if (!shallowEqual(nextState, _this.state)) {
            _this.setState(nextState);
          }
        };

        _this.disposable = new SerialDisposable();

        _this.receiveProps(props);

        _this.dispose();

        return _this;
      }

      _createClass$8(DragDropContainer, [{
        key: "getHandlerId",
        value: function getHandlerId() {
          return this.handlerId;
        }
      }, {
        key: "getDecoratedComponentInstance",
        value: function getDecoratedComponentInstance() {
          invariant(this.decoratedRef.current, 'In order to access an instance of the decorated component, it must either be a class component or use React.forwardRef()');
          return this.decoratedRef.current;
        }
      }, {
        key: "shouldComponentUpdate",
        value: function shouldComponentUpdate(nextProps, nextState) {
          return !arePropsEqual(nextProps, this.props) || !shallowEqual(nextState, this.state);
        }
      }, {
        key: "componentDidMount",
        value: function componentDidMount() {
          this.disposable = new SerialDisposable();
          this.currentType = undefined;
          this.receiveProps(this.props);
          this.handleChange();
        }
      }, {
        key: "componentDidUpdate",
        value: function componentDidUpdate(prevProps) {
          if (!arePropsEqual(this.props, prevProps)) {
            this.receiveProps(this.props);
            this.handleChange();
          }
        }
      }, {
        key: "componentWillUnmount",
        value: function componentWillUnmount() {
          this.dispose();
        }
      }, {
        key: "receiveProps",
        value: function receiveProps(props) {
          if (!this.handler) {
            return;
          }

          this.handler.receiveProps(props);
          this.receiveType(getType(props));
        }
      }, {
        key: "receiveType",
        value: function receiveType(type) {
          if (!this.handlerMonitor || !this.manager || !this.handlerConnector) {
            return;
          }

          if (type === this.currentType) {
            return;
          }

          this.currentType = type;

          var _registerHandler = registerHandler(type, this.handler, this.manager),
              _registerHandler2 = _slicedToArray$9(_registerHandler, 2),
              handlerId = _registerHandler2[0],
              unregister = _registerHandler2[1];

          this.handlerId = handlerId;
          this.handlerMonitor.receiveHandlerId(handlerId);
          this.handlerConnector.receiveHandlerId(handlerId);
          var globalMonitor = this.manager.getMonitor();
          var unsubscribe = globalMonitor.subscribeToStateChange(this.handleChange, {
            handlerIds: [handlerId]
          });
          this.disposable.setDisposable(new CompositeDisposable(new Disposable(unsubscribe), new Disposable(unregister)));
        }
      }, {
        key: "dispose",
        value: function dispose() {
          this.disposable.dispose();

          if (this.handlerConnector) {
            this.handlerConnector.receiveHandlerId(null);
          }
        }
      }, {
        key: "getCurrentState",
        value: function getCurrentState() {
          if (!this.handlerConnector) {
            return {};
          }

          var nextState = collect(this.handlerConnector.hooks, this.handlerMonitor, this.props);

          if ("development" !== 'production') {
            invariant(isPlainObject$1(nextState), 'Expected `collect` specified as the second argument to ' + '%s for %s to return a plain object of props to inject. ' + 'Instead, received %s.', containerDisplayName, displayName, nextState);
          }

          return nextState;
        }
      }, {
        key: "render",
        value: function render() {
          var _this2 = this;

          return React.createElement(DndContext.Consumer, null, function (_ref2) {
            var dragDropManager = _ref2.dragDropManager;

            _this2.receiveDragDropManager(dragDropManager);

            if (typeof requestAnimationFrame !== 'undefined') {
              requestAnimationFrame(function () {
                return _this2.handlerConnector.reconnect();
              });
            }

            return React.createElement(Decorated, Object.assign({}, _this2.props, _this2.getCurrentState(), {
              // NOTE: if Decorated is a Function Component, decoratedRef will not be populated unless it's a refforwarding component.
              ref: isRefable(Decorated) ? _this2.decoratedRef : null
            }));
          });
        }
      }, {
        key: "receiveDragDropManager",
        value: function receiveDragDropManager(dragDropManager) {
          if (this.manager !== undefined) {
            return;
          }

          invariant(dragDropManager !== undefined, 'Could not find the drag and drop manager in the context of %s. ' + 'Make sure to render a DndProvider component in your top-level component. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/troubleshooting#could-not-find-the-drag-and-drop-manager-in-the-context', displayName, displayName);

          if (dragDropManager === undefined) {
            return;
          }

          this.manager = dragDropManager;
          this.handlerMonitor = createMonitor(dragDropManager);
          this.handlerConnector = createConnector(dragDropManager.getBackend());
          this.handler = createHandler(this.handlerMonitor, this.decoratedRef);
        }
      }]);

      return DragDropContainer;
    }(React.Component);

    DragDropContainer.DecoratedComponent = DecoratedComponent;
    DragDropContainer.displayName = "".concat(containerDisplayName, "(").concat(displayName, ")");
    return hoistNonReactStatics_cjs(DragDropContainer, DecoratedComponent);
  }

  function _typeof$6(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$6 = function _typeof(obj) { return typeof obj; }; } else { _typeof$6 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$6(obj); }

  function isValidType(type, allowArray) {
    return typeof type === 'string' || _typeof$6(type) === 'symbol' || !!allowArray && Array.isArray(type) && type.every(function (t) {
      return isValidType(t, false);
    });
  }

  function _classCallCheck$9(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$9(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$9(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$9(Constructor.prototype, protoProps); if (staticProps) _defineProperties$9(Constructor, staticProps); return Constructor; }
  var ALLOWED_SPEC_METHODS = ['canDrag', 'beginDrag', 'isDragging', 'endDrag'];
  var REQUIRED_SPEC_METHODS = ['beginDrag'];

  var SourceImpl =
  /*#__PURE__*/
  function () {
    function SourceImpl(spec, monitor, ref) {
      var _this = this;

      _classCallCheck$9(this, SourceImpl);

      this.props = null;

      this.beginDrag = function () {
        if (!_this.props) {
          return;
        }

        var item = _this.spec.beginDrag(_this.props, _this.monitor, _this.ref.current);

        if ("development" !== 'production') {
          invariant(isPlainObject$1(item), 'beginDrag() must return a plain object that represents the dragged item. ' + 'Instead received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', item);
        }

        return item;
      };

      this.spec = spec;
      this.monitor = monitor;
      this.ref = ref;
    }

    _createClass$9(SourceImpl, [{
      key: "receiveProps",
      value: function receiveProps(props) {
        this.props = props;
      }
    }, {
      key: "canDrag",
      value: function canDrag() {
        if (!this.props) {
          return false;
        }

        if (!this.spec.canDrag) {
          return true;
        }

        return this.spec.canDrag(this.props, this.monitor);
      }
    }, {
      key: "isDragging",
      value: function isDragging(globalMonitor, sourceId) {
        if (!this.props) {
          return false;
        }

        if (!this.spec.isDragging) {
          return sourceId === globalMonitor.getSourceId();
        }

        return this.spec.isDragging(this.props, this.monitor);
      }
    }, {
      key: "endDrag",
      value: function endDrag() {
        if (!this.props) {
          return;
        }

        if (!this.spec.endDrag) {
          return;
        }

        this.spec.endDrag(this.props, this.monitor, getDecoratedComponent(this.ref));
      }
    }]);

    return SourceImpl;
  }();

  function createSourceFactory(spec) {
    Object.keys(spec).forEach(function (key) {
      invariant(ALLOWED_SPEC_METHODS.indexOf(key) > -1, 'Expected the drag source specification to only have ' + 'some of the following keys: %s. ' + 'Instead received a specification with an unexpected "%s" key. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', ALLOWED_SPEC_METHODS.join(', '), key);
      invariant(typeof spec[key] === 'function', 'Expected %s in the drag source specification to be a function. ' + 'Instead received a specification with %s: %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', key, key, spec[key]);
    });
    REQUIRED_SPEC_METHODS.forEach(function (key) {
      invariant(typeof spec[key] === 'function', 'Expected %s in the drag source specification to be a function. ' + 'Instead received a specification with %s: %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', key, key, spec[key]);
    });
    return function createSource(monitor, ref) {
      return new SourceImpl(spec, monitor, ref);
    };
  }

  /**
   * Decorates a component as a dragsource
   * @param type The dragsource type
   * @param spec The drag source specification
   * @param collect The props collector function
   * @param options DnD options
   */

  function DragSource(type, spec, collect) {
    var options = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : {};
    checkDecoratorArguments('DragSource', 'type, spec, collect[, options]', type, spec, collect, options);
    var getType = type;

    if (typeof type !== 'function') {
      invariant(isValidType(type), 'Expected "type" provided as the first argument to DragSource to be ' + 'a string, or a function that returns a string given the current props. ' + 'Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', type);

      getType = function getType() {
        return type;
      };
    }

    invariant(isPlainObject$1(spec), 'Expected "spec" provided as the second argument to DragSource to be ' + 'a plain object. Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', spec);
    var createSource = createSourceFactory(spec);
    invariant(typeof collect === 'function', 'Expected "collect" provided as the third argument to DragSource to be ' + 'a function that returns a plain object of props to inject. ' + 'Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', collect);
    invariant(isPlainObject$1(options), 'Expected "options" provided as the fourth argument to DragSource to be ' + 'a plain object when specified. ' + 'Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-source', collect);
    return function decorateSource(DecoratedComponent) {
      return decorateHandler({
        containerDisplayName: 'DragSource',
        createHandler: createSource,
        registerHandler: registerSource,
        createConnector: function createConnector(backend) {
          return new SourceConnector(backend);
        },
        createMonitor: function createMonitor(manager) {
          return new DragSourceMonitorImpl(manager);
        },
        DecoratedComponent: DecoratedComponent,
        getType: getType,
        collect: collect,
        options: options
      });
    };
  }

  function _classCallCheck$a(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$a(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$a(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$a(Constructor.prototype, protoProps); if (staticProps) _defineProperties$a(Constructor, staticProps); return Constructor; }
  var ALLOWED_SPEC_METHODS$1 = ['canDrop', 'hover', 'drop'];

  var TargetImpl =
  /*#__PURE__*/
  function () {
    function TargetImpl(spec, monitor, ref) {
      _classCallCheck$a(this, TargetImpl);

      this.props = null;
      this.spec = spec;
      this.monitor = monitor;
      this.ref = ref;
    }

    _createClass$a(TargetImpl, [{
      key: "receiveProps",
      value: function receiveProps(props) {
        this.props = props;
      }
    }, {
      key: "receiveMonitor",
      value: function receiveMonitor(monitor) {
        this.monitor = monitor;
      }
    }, {
      key: "canDrop",
      value: function canDrop() {
        if (!this.spec.canDrop) {
          return true;
        }

        return this.spec.canDrop(this.props, this.monitor);
      }
    }, {
      key: "hover",
      value: function hover() {
        if (!this.spec.hover) {
          return;
        }

        this.spec.hover(this.props, this.monitor, getDecoratedComponent(this.ref));
      }
    }, {
      key: "drop",
      value: function drop() {
        if (!this.spec.drop) {
          return undefined;
        }

        var dropResult = this.spec.drop(this.props, this.monitor, this.ref.current);

        if ("development" !== 'production') {
          invariant(typeof dropResult === 'undefined' || isPlainObject$1(dropResult), 'drop() must either return undefined, or an object that represents the drop result. ' + 'Instead received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', dropResult);
        }

        return dropResult;
      }
    }]);

    return TargetImpl;
  }();

  function createTargetFactory(spec) {
    Object.keys(spec).forEach(function (key) {
      invariant(ALLOWED_SPEC_METHODS$1.indexOf(key) > -1, 'Expected the drop target specification to only have ' + 'some of the following keys: %s. ' + 'Instead received a specification with an unexpected "%s" key. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', ALLOWED_SPEC_METHODS$1.join(', '), key);
      invariant(typeof spec[key] === 'function', 'Expected %s in the drop target specification to be a function. ' + 'Instead received a specification with %s: %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', key, key, spec[key]);
    });
    return function createTarget(monitor, ref) {
      return new TargetImpl(spec, monitor, ref);
    };
  }

  function DropTarget(type, spec, collect) {
    var options = arguments.length > 3 && arguments[3] !== undefined ? arguments[3] : {};
    checkDecoratorArguments('DropTarget', 'type, spec, collect[, options]', type, spec, collect, options);
    var getType = type;

    if (typeof type !== 'function') {
      invariant(isValidType(type, true), 'Expected "type" provided as the first argument to DropTarget to be ' + 'a string, an array of strings, or a function that returns either given ' + 'the current props. Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', type);

      getType = function getType() {
        return type;
      };
    }

    invariant(isPlainObject$1(spec), 'Expected "spec" provided as the second argument to DropTarget to be ' + 'a plain object. Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', spec);
    var createTarget = createTargetFactory(spec);
    invariant(typeof collect === 'function', 'Expected "collect" provided as the third argument to DropTarget to be ' + 'a function that returns a plain object of props to inject. ' + 'Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', collect);
    invariant(isPlainObject$1(options), 'Expected "options" provided as the fourth argument to DropTarget to be ' + 'a plain object when specified. ' + 'Instead, received %s. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/api/drop-target', collect);
    return function decorateTarget(DecoratedComponent) {
      return decorateHandler({
        containerDisplayName: 'DropTarget',
        createHandler: createTarget,
        registerHandler: registerTarget,
        createMonitor: function createMonitor(manager) {
          return new DropTargetMonitorImpl(manager);
        },
        createConnector: function createConnector(backend) {
          return new TargetConnector(backend);
        },
        DecoratedComponent: DecoratedComponent,
        getType: getType,
        collect: collect,
        options: options
      });
    };
  }

  function _typeof$7(obj) { if (typeof Symbol === "function" && typeof Symbol.iterator === "symbol") { _typeof$7 = function _typeof(obj) { return typeof obj; }; } else { _typeof$7 = function _typeof(obj) { return obj && typeof Symbol === "function" && obj.constructor === Symbol && obj !== Symbol.prototype ? "symbol" : typeof obj; }; } return _typeof$7(obj); }

  function _classCallCheck$b(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

  function _defineProperties$b(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }

  function _createClass$b(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties$b(Constructor.prototype, protoProps); if (staticProps) _defineProperties$b(Constructor, staticProps); return Constructor; }

  function _possibleConstructorReturn$1(self, call) { if (call && (_typeof$7(call) === "object" || typeof call === "function")) { return call; } return _assertThisInitialized$1(self); }

  function _assertThisInitialized$1(self) { if (self === void 0) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return self; }

  function _getPrototypeOf$1(o) { _getPrototypeOf$1 = Object.setPrototypeOf ? Object.getPrototypeOf : function _getPrototypeOf(o) { return o.__proto__ || Object.getPrototypeOf(o); }; return _getPrototypeOf$1(o); }

  function _inherits$1(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, writable: true, configurable: true } }); if (superClass) _setPrototypeOf$1(subClass, superClass); }

  function _setPrototypeOf$1(o, p) { _setPrototypeOf$1 = Object.setPrototypeOf || function _setPrototypeOf(o, p) { o.__proto__ = p; return o; }; return _setPrototypeOf$1(o, p); }
  function DragLayer(collect) {
    var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
    checkDecoratorArguments('DragLayer', 'collect[, options]', collect, options);
    invariant(typeof collect === 'function', 'Expected "collect" provided as the first argument to DragLayer to be a function that collects props to inject into the component. ', 'Instead, received %s. Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-layer', collect);
    invariant(isPlainObject$1(options), 'Expected "options" provided as the second argument to DragLayer to be a plain object when specified. ' + 'Instead, received %s. Read more: http://react-dnd.github.io/react-dnd/docs/api/drag-layer', options);
    return function decorateLayer(DecoratedComponent) {
      var Decorated = DecoratedComponent;
      var _options$arePropsEqua = options.arePropsEqual,
          arePropsEqual = _options$arePropsEqua === void 0 ? shallowEqual : _options$arePropsEqua;
      var displayName = Decorated.displayName || Decorated.name || 'Component';

      var DragLayerContainer =
      /*#__PURE__*/
      function (_React$Component) {
        _inherits$1(DragLayerContainer, _React$Component);

        function DragLayerContainer() {
          var _this;

          _classCallCheck$b(this, DragLayerContainer);

          _this = _possibleConstructorReturn$1(this, _getPrototypeOf$1(DragLayerContainer).apply(this, arguments));
          _this.isCurrentlyMounted = false;
          _this.ref = React.createRef();

          _this.handleChange = function () {
            if (!_this.isCurrentlyMounted) {
              return;
            }

            var nextState = _this.getCurrentState();

            if (!shallowEqual(nextState, _this.state)) {
              _this.setState(nextState);
            }
          };

          return _this;
        }

        _createClass$b(DragLayerContainer, [{
          key: "getDecoratedComponentInstance",
          value: function getDecoratedComponentInstance() {
            invariant(this.ref.current, 'In order to access an instance of the decorated component, it must either be a class component or use React.forwardRef()');
            return this.ref.current;
          }
        }, {
          key: "shouldComponentUpdate",
          value: function shouldComponentUpdate(nextProps, nextState) {
            return !arePropsEqual(nextProps, this.props) || !shallowEqual(nextState, this.state);
          }
        }, {
          key: "componentDidMount",
          value: function componentDidMount() {
            this.isCurrentlyMounted = true;
            this.handleChange();
          }
        }, {
          key: "componentWillUnmount",
          value: function componentWillUnmount() {
            this.isCurrentlyMounted = false;

            if (this.unsubscribeFromOffsetChange) {
              this.unsubscribeFromOffsetChange();
              this.unsubscribeFromOffsetChange = undefined;
            }

            if (this.unsubscribeFromStateChange) {
              this.unsubscribeFromStateChange();
              this.unsubscribeFromStateChange = undefined;
            }
          }
        }, {
          key: "render",
          value: function render() {
            var _this2 = this;

            return React.createElement(DndContext.Consumer, null, function (_ref) {
              var dragDropManager = _ref.dragDropManager;

              if (dragDropManager === undefined) {
                return null;
              }

              _this2.receiveDragDropManager(dragDropManager); // Let componentDidMount fire to initialize the collected state


              if (!_this2.isCurrentlyMounted) {
                return null;
              }

              return React.createElement(Decorated, Object.assign({}, _this2.props, _this2.state, {
                ref: isRefable(Decorated) ? _this2.ref : null
              }));
            });
          }
        }, {
          key: "receiveDragDropManager",
          value: function receiveDragDropManager(dragDropManager) {
            if (this.manager !== undefined) {
              return;
            }

            this.manager = dragDropManager;
            invariant(_typeof$7(dragDropManager) === 'object', 'Could not find the drag and drop manager in the context of %s. ' + 'Make sure to render a DndProvider component in your top-level component. ' + 'Read more: http://react-dnd.github.io/react-dnd/docs/troubleshooting#could-not-find-the-drag-and-drop-manager-in-the-context', displayName, displayName);
            var monitor = this.manager.getMonitor();
            this.unsubscribeFromOffsetChange = monitor.subscribeToOffsetChange(this.handleChange);
            this.unsubscribeFromStateChange = monitor.subscribeToStateChange(this.handleChange);
          }
        }, {
          key: "getCurrentState",
          value: function getCurrentState() {
            if (!this.manager) {
              return {};
            }

            var monitor = this.manager.getMonitor();
            return collect(monitor, this.props);
          }
        }]);

        return DragLayerContainer;
      }(React.Component);

      DragLayerContainer.displayName = "DragLayer(".concat(displayName, ")");
      DragLayerContainer.DecoratedComponent = DecoratedComponent;
      return hoistNonReactStatics_cjs(DragLayerContainer, DecoratedComponent);
    };
  }

  exports.DndContext = DndContext;
  exports.DndProvider = DndProvider;
  exports.DragLayer = DragLayer;
  exports.DragPreviewImage = DragPreviewImage;
  exports.DragSource = DragSource;
  exports.DropTarget = DropTarget;
  exports.createDndContext = createDndContext;
  exports.useDrag = useDrag;
  exports.useDragLayer = useDragLayer;
  exports.useDrop = useDrop;

  Object.defineProperty(exports, '__esModule', { value: true });

})));