react-dom-unstable-native-dependencies.development.js

/** @license React v16.4.2
 * react-dom-unstable-native-dependencies.development.js
 *
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

'use strict';



if (process.env.NODE_ENV !== "production") {
  (function() {
'use strict';

var ReactDOM = require('react-dom');
var invariant = require('fbjs/lib/invariant');
var warning = require('fbjs/lib/warning');
var _assign = require('object-assign');
var emptyFunction = require('fbjs/lib/emptyFunction');

// Relying on the `invariant()` implementation lets us
// have preserve the format and params in the www builds.

{
  // In DEV mode, we swap out invokeGuardedCallback for a special version
  // that plays more nicely with the browser's DevTools. The idea is to preserve
  // "Pause on exceptions" behavior. Because React wraps all user-provided
  // functions in invokeGuardedCallback, and the production version of
  // invokeGuardedCallback uses a try-catch, all user exceptions are treated
  // like caught exceptions, and the DevTools won't pause unless the developer
  // takes the extra step of enabling pause on caught exceptions. This is
  // untintuitive, though, because even though React has caught the error, from
  // the developer's perspective, the error is uncaught.
  //
  // To preserve the expected "Pause on exceptions" behavior, we don't use a
  // try-catch in DEV. Instead, we synchronously dispatch a fake event to a fake
  // DOM node, and call the user-provided callback from inside an event handler
  // for that fake event. If the callback throws, the error is "captured" using
  // a global event handler. But because the error happens in a different
  // event loop context, it does not interrupt the normal program flow.
  // Effectively, this gives us try-catch behavior without actually using
  // try-catch. Neat!

  // Check that the browser supports the APIs we need to implement our special
  // DEV version of invokeGuardedCallback
  if (typeof window !== 'undefined' && typeof window.dispatchEvent === 'function' && typeof document !== 'undefined' && typeof document.createEvent === 'function') {
    var fakeNode = document.createElement('react');

    
  }
}

var getFiberCurrentPropsFromNode = null;
var getInstanceFromNode = null;
var getNodeFromInstance = null;

var injection = {
  injectComponentTree: function (Injected) {
    getFiberCurrentPropsFromNode = Injected.getFiberCurrentPropsFromNode;
    getInstanceFromNode = Injected.getInstanceFromNode;
    getNodeFromInstance = Injected.getNodeFromInstance;

    {
      !(getNodeFromInstance && getInstanceFromNode) ? warning(false, 'EventPluginUtils.injection.injectComponentTree(...): Injected ' + 'module is missing getNodeFromInstance or getInstanceFromNode.') : void 0;
    }
  }
};

var validateEventDispatches = void 0;
{
  validateEventDispatches = function (event) {
    var dispatchListeners = event._dispatchListeners;
    var dispatchInstances = event._dispatchInstances;

    var listenersIsArr = Array.isArray(dispatchListeners);
    var listenersLen = listenersIsArr ? dispatchListeners.length : dispatchListeners ? 1 : 0;

    var instancesIsArr = Array.isArray(dispatchInstances);
    var instancesLen = instancesIsArr ? dispatchInstances.length : dispatchInstances ? 1 : 0;

    !(instancesIsArr === listenersIsArr && instancesLen === listenersLen) ? warning(false, 'EventPluginUtils: Invalid `event`.') : void 0;
  };
}

/**
 * Standard/simple iteration through an event's collected dispatches.
 */


/**
 * Standard/simple iteration through an event's collected dispatches, but stops
 * at the first dispatch execution returning true, and returns that id.
 *
 * @return {?string} id of the first dispatch execution who's listener returns
 * true, or null if no listener returned true.
 */
function executeDispatchesInOrderStopAtTrueImpl(event) {
  var dispatchListeners = event._dispatchListeners;
  var dispatchInstances = event._dispatchInstances;
  {
    validateEventDispatches(event);
  }
  if (Array.isArray(dispatchListeners)) {
    for (var i = 0; i < dispatchListeners.length; i++) {
      if (event.isPropagationStopped()) {
        break;
      }
      // Listeners and Instances are two parallel arrays that are always in sync.
      if (dispatchListeners[i](event, dispatchInstances[i])) {
        return dispatchInstances[i];
      }
    }
  } else if (dispatchListeners) {
    if (dispatchListeners(event, dispatchInstances)) {
      return dispatchInstances;
    }
  }
  return null;
}

/**
 * @see executeDispatchesInOrderStopAtTrueImpl
 */
function executeDispatchesInOrderStopAtTrue(event) {
  var ret = executeDispatchesInOrderStopAtTrueImpl(event);
  event._dispatchInstances = null;
  event._dispatchListeners = null;
  return ret;
}

/**
 * Execution of a "direct" dispatch - there must be at most one dispatch
 * accumulated on the event or it is considered an error. It doesn't really make
 * sense for an event with multiple dispatches (bubbled) to keep track of the
 * return values at each dispatch execution, but it does tend to make sense when
 * dealing with "direct" dispatches.
 *
 * @return {*} The return value of executing the single dispatch.
 */
function executeDirectDispatch(event) {
  {
    validateEventDispatches(event);
  }
  var dispatchListener = event._dispatchListeners;
  var dispatchInstance = event._dispatchInstances;
  !!Array.isArray(dispatchListener) ? invariant(false, 'executeDirectDispatch(...): Invalid `event`.') : void 0;
  event.currentTarget = dispatchListener ? getNodeFromInstance(dispatchInstance) : null;
  var res = dispatchListener ? dispatchListener(event) : null;
  event.currentTarget = null;
  event._dispatchListeners = null;
  event._dispatchInstances = null;
  return res;
}

/**
 * @param {SyntheticEvent} event
 * @return {boolean} True iff number of dispatches accumulated is greater than 0.
 */
function hasDispatches(event) {
  return !!event._dispatchListeners;
}

// Before we know whether it is functional or class


 // Root of a host tree. Could be nested inside another node.
 // A subtree. Could be an entry point to a different renderer.
var HostComponent = 5;

function getParent(inst) {
  do {
    inst = inst.return;
    // TODO: If this is a HostRoot we might want to bail out.
    // That is depending on if we want nested subtrees (layers) to bubble
    // events to their parent. We could also go through parentNode on the
    // host node but that wouldn't work for React Native and doesn't let us
    // do the portal feature.
  } while (inst && inst.tag !== HostComponent);
  if (inst) {
    return inst;
  }
  return null;
}

/**
 * Return the lowest common ancestor of A and B, or null if they are in
 * different trees.
 */
function getLowestCommonAncestor(instA, instB) {
  var depthA = 0;
  for (var tempA = instA; tempA; tempA = getParent(tempA)) {
    depthA++;
  }
  var depthB = 0;
  for (var tempB = instB; tempB; tempB = getParent(tempB)) {
    depthB++;
  }

  // If A is deeper, crawl up.
  while (depthA - depthB > 0) {
    instA = getParent(instA);
    depthA--;
  }

  // If B is deeper, crawl up.
  while (depthB - depthA > 0) {
    instB = getParent(instB);
    depthB--;
  }

  // Walk in lockstep until we find a match.
  var depth = depthA;
  while (depth--) {
    if (instA === instB || instA === instB.alternate) {
      return instA;
    }
    instA = getParent(instA);
    instB = getParent(instB);
  }
  return null;
}

/**
 * Return if A is an ancestor of B.
 */
function isAncestor(instA, instB) {
  while (instB) {
    if (instA === instB || instA === instB.alternate) {
      return true;
    }
    instB = getParent(instB);
  }
  return false;
}

/**
 * Return the parent instance of the passed-in instance.
 */
function getParentInstance(inst) {
  return getParent(inst);
}

/**
 * Simulates the traversal of a two-phase, capture/bubble event dispatch.
 */
function traverseTwoPhase(inst, fn, arg) {
  var path = [];
  while (inst) {
    path.push(inst);
    inst = getParent(inst);
  }
  var i = void 0;
  for (i = path.length; i-- > 0;) {
    fn(path[i], 'captured', arg);
  }
  for (i = 0; i < path.length; i++) {
    fn(path[i], 'bubbled', arg);
  }
}

/**
 * Traverses the ID hierarchy and invokes the supplied `cb` on any IDs that
 * should would receive a `mouseEnter` or `mouseLeave` event.
 *
 * Does not invoke the callback on the nearest common ancestor because nothing
 * "entered" or "left" that element.
 */

/**
 * Registers plugins so that they can extract and dispatch events.
 *
 * @see {EventPluginHub}
 */

/**
 * Ordered list of injected plugins.
 */


/**
 * Mapping from event name to dispatch config
 */


/**
 * Mapping from registration name to plugin module
 */


/**
 * Mapping from registration name to event name
 */


/**
 * Mapping from lowercase registration names to the properly cased version,
 * used to warn in the case of missing event handlers. Available
 * only in true.
 * @type {Object}
 */

// Trust the developer to only use possibleRegistrationNames in true

/**
 * Injects an ordering of plugins (by plugin name). This allows the ordering
 * to be decoupled from injection of the actual plugins so that ordering is
 * always deterministic regardless of packaging, on-the-fly injection, etc.
 *
 * @param {array} InjectedEventPluginOrder
 * @internal
 * @see {EventPluginHub.injection.injectEventPluginOrder}
 */


/**
 * Injects plugins to be used by `EventPluginHub`. The plugin names must be
 * in the ordering injected by `injectEventPluginOrder`.
 *
 * Plugins can be injected as part of page initialization or on-the-fly.
 *
 * @param {object} injectedNamesToPlugins Map from names to plugin modules.
 * @internal
 * @see {EventPluginHub.injection.injectEventPluginsByName}
 */

/**
 * Accumulates items that must not be null or undefined into the first one. This
 * is used to conserve memory by avoiding array allocations, and thus sacrifices
 * API cleanness. Since `current` can be null before being passed in and not
 * null after this function, make sure to assign it back to `current`:
 *
 * `a = accumulateInto(a, b);`
 *
 * This API should be sparingly used. Try `accumulate` for something cleaner.
 *
 * @return {*|array<*>} An accumulation of items.
 */

function accumulateInto(current, next) {
  !(next != null) ? invariant(false, 'accumulateInto(...): Accumulated items must not be null or undefined.') : void 0;

  if (current == null) {
    return next;
  }

  // Both are not empty. Warning: Never call x.concat(y) when you are not
  // certain that x is an Array (x could be a string with concat method).
  if (Array.isArray(current)) {
    if (Array.isArray(next)) {
      current.push.apply(current, next);
      return current;
    }
    current.push(next);
    return current;
  }

  if (Array.isArray(next)) {
    // A bit too dangerous to mutate `next`.
    return [current].concat(next);
  }

  return [current, next];
}

/**
 * @param {array} arr an "accumulation" of items which is either an Array or
 * a single item. Useful when paired with the `accumulate` module. This is a
 * simple utility that allows us to reason about a collection of items, but
 * handling the case when there is exactly one item (and we do not need to
 * allocate an array).
 * @param {function} cb Callback invoked with each element or a collection.
 * @param {?} [scope] Scope used as `this` in a callback.
 */
function forEachAccumulated(arr, cb, scope) {
  if (Array.isArray(arr)) {
    arr.forEach(cb, scope);
  } else if (arr) {
    cb.call(scope, arr);
  }
}

function isInteractive(tag) {
  return tag === 'button' || tag === 'input' || tag === 'select' || tag === 'textarea';
}

function shouldPreventMouseEvent(name, type, props) {
  switch (name) {
    case 'onClick':
    case 'onClickCapture':
    case 'onDoubleClick':
    case 'onDoubleClickCapture':
    case 'onMouseDown':
    case 'onMouseDownCapture':
    case 'onMouseMove':
    case 'onMouseMoveCapture':
    case 'onMouseUp':
    case 'onMouseUpCapture':
      return !!(props.disabled && isInteractive(type));
    default:
      return false;
  }
}

/**
 * This is a unified interface for event plugins to be installed and configured.
 *
 * Event plugins can implement the following properties:
 *
 *   `extractEvents` {function(string, DOMEventTarget, string, object): *}
 *     Required. When a top-level event is fired, this method is expected to
 *     extract synthetic events that will in turn be queued and dispatched.
 *
 *   `eventTypes` {object}
 *     Optional, plugins that fire events must publish a mapping of registration
 *     names that are used to register listeners. Values of this mapping must
 *     be objects that contain `registrationName` or `phasedRegistrationNames`.
 *
 *   `executeDispatch` {function(object, function, string)}
 *     Optional, allows plugins to override how an event gets dispatched. By
 *     default, the listener is simply invoked.
 *
 * Each plugin that is injected into `EventsPluginHub` is immediately operable.
 *
 * @public
 */

/**
 * Methods for injecting dependencies.
 */


/**
 * @param {object} inst The instance, which is the source of events.
 * @param {string} registrationName Name of listener (e.g. `onClick`).
 * @return {?function} The stored callback.
 */
function getListener(inst, registrationName) {
  var listener = void 0;

  // TODO: shouldPreventMouseEvent is DOM-specific and definitely should not
  // live here; needs to be moved to a better place soon
  var stateNode = inst.stateNode;
  if (!stateNode) {
    // Work in progress (ex: onload events in incremental mode).
    return null;
  }
  var props = getFiberCurrentPropsFromNode(stateNode);
  if (!props) {
    // Work in progress.
    return null;
  }
  listener = props[registrationName];
  if (shouldPreventMouseEvent(registrationName, inst.type, props)) {
    return null;
  }
  !(!listener || typeof listener === 'function') ? invariant(false, 'Expected `%s` listener to be a function, instead got a value of `%s` type.', registrationName, typeof listener) : void 0;
  return listener;
}

/**
 * Some event types have a notion of different registration names for different
 * "phases" of propagation. This finds listeners by a given phase.
 */
function listenerAtPhase(inst, event, propagationPhase) {
  var registrationName = event.dispatchConfig.phasedRegistrationNames[propagationPhase];
  return getListener(inst, registrationName);
}

/**
 * A small set of propagation patterns, each of which will accept a small amount
 * of information, and generate a set of "dispatch ready event objects" - which
 * are sets of events that have already been annotated with a set of dispatched
 * listener functions/ids. The API is designed this way to discourage these
 * propagation strategies from actually executing the dispatches, since we
 * always want to collect the entire set of dispatches before executing even a
 * single one.
 */

/**
 * Tags a `SyntheticEvent` with dispatched listeners. Creating this function
 * here, allows us to not have to bind or create functions for each event.
 * Mutating the event's members allows us to not have to create a wrapping
 * "dispatch" object that pairs the event with the listener.
 */
function accumulateDirectionalDispatches(inst, phase, event) {
  {
    !inst ? warning(false, 'Dispatching inst must not be null') : void 0;
  }
  var listener = listenerAtPhase(inst, event, phase);
  if (listener) {
    event._dispatchListeners = accumulateInto(event._dispatchListeners, listener);
    event._dispatchInstances = accumulateInto(event._dispatchInstances, inst);
  }
}

/**
 * Collect dispatches (must be entirely collected before dispatching - see unit
 * tests). Lazily allocate the array to conserve memory.  We must loop through
 * each event and perform the traversal for each one. We cannot perform a
 * single traversal for the entire collection of events because each event may
 * have a different target.
 */
function accumulateTwoPhaseDispatchesSingle(event) {
  if (event && event.dispatchConfig.phasedRegistrationNames) {
    traverseTwoPhase(event._targetInst, accumulateDirectionalDispatches, event);
  }
}

/**
 * Same as `accumulateTwoPhaseDispatchesSingle`, but skips over the targetID.
 */
function accumulateTwoPhaseDispatchesSingleSkipTarget(event) {
  if (event && event.dispatchConfig.phasedRegistrationNames) {
    var targetInst = event._targetInst;
    var parentInst = targetInst ? getParentInstance(targetInst) : null;
    traverseTwoPhase(parentInst, accumulateDirectionalDispatches, event);
  }
}

/**
 * Accumulates without regard to direction, does not look for phased
 * registration names. Same as `accumulateDirectDispatchesSingle` but without
 * requiring that the `dispatchMarker` be the same as the dispatched ID.
 */
function accumulateDispatches(inst, ignoredDirection, event) {
  if (inst && event && event.dispatchConfig.registrationName) {
    var registrationName = event.dispatchConfig.registrationName;
    var listener = getListener(inst, registrationName);
    if (listener) {
      event._dispatchListeners = accumulateInto(event._dispatchListeners, listener);
      event._dispatchInstances = accumulateInto(event._dispatchInstances, inst);
    }
  }
}

/**
 * Accumulates dispatches on an `SyntheticEvent`, but only for the
 * `dispatchMarker`.
 * @param {SyntheticEvent} event
 */
function accumulateDirectDispatchesSingle(event) {
  if (event && event.dispatchConfig.registrationName) {
    accumulateDispatches(event._targetInst, null, event);
  }
}

function accumulateTwoPhaseDispatches(events) {
  forEachAccumulated(events, accumulateTwoPhaseDispatchesSingle);
}

function accumulateTwoPhaseDispatchesSkipTarget(events) {
  forEachAccumulated(events, accumulateTwoPhaseDispatchesSingleSkipTarget);
}



function accumulateDirectDispatches(events) {
  forEachAccumulated(events, accumulateDirectDispatchesSingle);
}

/* eslint valid-typeof: 0 */

var didWarnForAddedNewProperty = false;
var EVENT_POOL_SIZE = 10;

var shouldBeReleasedProperties = ['dispatchConfig', '_targetInst', 'nativeEvent', 'isDefaultPrevented', 'isPropagationStopped', '_dispatchListeners', '_dispatchInstances'];

/**
 * @interface Event
 * @see http://www.w3.org/TR/DOM-Level-3-Events/
 */
var EventInterface = {
  type: null,
  target: null,
  // currentTarget is set when dispatching; no use in copying it here
  currentTarget: emptyFunction.thatReturnsNull,
  eventPhase: null,
  bubbles: null,
  cancelable: null,
  timeStamp: function (event) {
    return event.timeStamp || Date.now();
  },
  defaultPrevented: null,
  isTrusted: null
};

/**
 * Synthetic events are dispatched by event plugins, typically in response to a
 * top-level event delegation handler.
 *
 * These systems should generally use pooling to reduce the frequency of garbage
 * collection. The system should check `isPersistent` to determine whether the
 * event should be released into the pool after being dispatched. Users that
 * need a persisted event should invoke `persist`.
 *
 * Synthetic events (and subclasses) implement the DOM Level 3 Events API by
 * normalizing browser quirks. Subclasses do not necessarily have to implement a
 * DOM interface; custom application-specific events can also subclass this.
 *
 * @param {object} dispatchConfig Configuration used to dispatch this event.
 * @param {*} targetInst Marker identifying the event target.
 * @param {object} nativeEvent Native browser event.
 * @param {DOMEventTarget} nativeEventTarget Target node.
 */
function SyntheticEvent(dispatchConfig, targetInst, nativeEvent, nativeEventTarget) {
  {
    // these have a getter/setter for warnings
    delete this.nativeEvent;
    delete this.preventDefault;
    delete this.stopPropagation;
  }

  this.dispatchConfig = dispatchConfig;
  this._targetInst = targetInst;
  this.nativeEvent = nativeEvent;

  var Interface = this.constructor.Interface;
  for (var propName in Interface) {
    if (!Interface.hasOwnProperty(propName)) {
      continue;
    }
    {
      delete this[propName]; // this has a getter/setter for warnings
    }
    var normalize = Interface[propName];
    if (normalize) {
      this[propName] = normalize(nativeEvent);
    } else {
      if (propName === 'target') {
        this.target = nativeEventTarget;
      } else {
        this[propName] = nativeEvent[propName];
      }
    }
  }

  var defaultPrevented = nativeEvent.defaultPrevented != null ? nativeEvent.defaultPrevented : nativeEvent.returnValue === false;
  if (defaultPrevented) {
    this.isDefaultPrevented = emptyFunction.thatReturnsTrue;
  } else {
    this.isDefaultPrevented = emptyFunction.thatReturnsFalse;
  }
  this.isPropagationStopped = emptyFunction.thatReturnsFalse;
  return this;
}

_assign(SyntheticEvent.prototype, {
  preventDefault: function () {
    this.defaultPrevented = true;
    var event = this.nativeEvent;
    if (!event) {
      return;
    }

    if (event.preventDefault) {
      event.preventDefault();
    } else if (typeof event.returnValue !== 'unknown') {
      event.returnValue = false;
    }
    this.isDefaultPrevented = emptyFunction.thatReturnsTrue;
  },

  stopPropagation: function () {
    var event = this.nativeEvent;
    if (!event) {
      return;
    }

    if (event.stopPropagation) {
      event.stopPropagation();
    } else if (typeof event.cancelBubble !== 'unknown') {
      // The ChangeEventPlugin registers a "propertychange" event for
      // IE. This event does not support bubbling or cancelling, and
      // any references to cancelBubble throw "Member not found".  A
      // typeof check of "unknown" circumvents this issue (and is also
      // IE specific).
      event.cancelBubble = true;
    }

    this.isPropagationStopped = emptyFunction.thatReturnsTrue;
  },

  /**
   * We release all dispatched `SyntheticEvent`s after each event loop, adding
   * them back into the pool. This allows a way to hold onto a reference that
   * won't be added back into the pool.
   */
  persist: function () {
    this.isPersistent = emptyFunction.thatReturnsTrue;
  },

  /**
   * Checks if this event should be released back into the pool.
   *
   * @return {boolean} True if this should not be released, false otherwise.
   */
  isPersistent: emptyFunction.thatReturnsFalse,

  /**
   * `PooledClass` looks for `destructor` on each instance it releases.
   */
  destructor: function () {
    var Interface = this.constructor.Interface;
    for (var propName in Interface) {
      {
        Object.defineProperty(this, propName, getPooledWarningPropertyDefinition(propName, Interface[propName]));
      }
    }
    for (var i = 0; i < shouldBeReleasedProperties.length; i++) {
      this[shouldBeReleasedProperties[i]] = null;
    }
    {
      Object.defineProperty(this, 'nativeEvent', getPooledWarningPropertyDefinition('nativeEvent', null));
      Object.defineProperty(this, 'preventDefault', getPooledWarningPropertyDefinition('preventDefault', emptyFunction));
      Object.defineProperty(this, 'stopPropagation', getPooledWarningPropertyDefinition('stopPropagation', emptyFunction));
    }
  }
});

SyntheticEvent.Interface = EventInterface;

/**
 * Helper to reduce boilerplate when creating subclasses.
 */
SyntheticEvent.extend = function (Interface) {
  var Super = this;

  var E = function () {};
  E.prototype = Super.prototype;
  var prototype = new E();

  function Class() {
    return Super.apply(this, arguments);
  }
  _assign(prototype, Class.prototype);
  Class.prototype = prototype;
  Class.prototype.constructor = Class;

  Class.Interface = _assign({}, Super.Interface, Interface);
  Class.extend = Super.extend;
  addEventPoolingTo(Class);

  return Class;
};

/** Proxying after everything set on SyntheticEvent
 * to resolve Proxy issue on some WebKit browsers
 * in which some Event properties are set to undefined (GH#10010)
 */
{
  var isProxySupported = typeof Proxy === 'function' &&
  // https://github.com/facebook/react/issues/12011
  !Object.isSealed(new Proxy({}, {}));

  if (isProxySupported) {
    /*eslint-disable no-func-assign */
    SyntheticEvent = new Proxy(SyntheticEvent, {
      construct: function (target, args) {
        return this.apply(target, Object.create(target.prototype), args);
      },
      apply: function (constructor, that, args) {
        return new Proxy(constructor.apply(that, args), {
          set: function (target, prop, value) {
            if (prop !== 'isPersistent' && !target.constructor.Interface.hasOwnProperty(prop) && shouldBeReleasedProperties.indexOf(prop) === -1) {
              !(didWarnForAddedNewProperty || target.isPersistent()) ? warning(false, "This synthetic event is reused for performance reasons. If you're " + "seeing this, you're adding a new property in the synthetic event object. " + 'The property is never released. See ' + 'https://fb.me/react-event-pooling for more information.') : void 0;
              didWarnForAddedNewProperty = true;
            }
            target[prop] = value;
            return true;
          }
        });
      }
    });
    /*eslint-enable no-func-assign */
  }
}

addEventPoolingTo(SyntheticEvent);

/**
 * Helper to nullify syntheticEvent instance properties when destructing
 *
 * @param {String} propName
 * @param {?object} getVal
 * @return {object} defineProperty object
 */
function getPooledWarningPropertyDefinition(propName, getVal) {
  var isFunction = typeof getVal === 'function';
  return {
    configurable: true,
    set: set,
    get: get
  };

  function set(val) {
    var action = isFunction ? 'setting the method' : 'setting the property';
    warn(action, 'This is effectively a no-op');
    return val;
  }

  function get() {
    var action = isFunction ? 'accessing the method' : 'accessing the property';
    var result = isFunction ? 'This is a no-op function' : 'This is set to null';
    warn(action, result);
    return getVal;
  }

  function warn(action, result) {
    var warningCondition = false;
    !warningCondition ? warning(false, "This synthetic event is reused for performance reasons. If you're seeing this, " + "you're %s `%s` on a released/nullified synthetic event. %s. " + 'If you must keep the original synthetic event around, use event.persist(). ' + 'See https://fb.me/react-event-pooling for more information.', action, propName, result) : void 0;
  }
}

function getPooledEvent(dispatchConfig, targetInst, nativeEvent, nativeInst) {
  var EventConstructor = this;
  if (EventConstructor.eventPool.length) {
    var instance = EventConstructor.eventPool.pop();
    EventConstructor.call(instance, dispatchConfig, targetInst, nativeEvent, nativeInst);
    return instance;
  }
  return new EventConstructor(dispatchConfig, targetInst, nativeEvent, nativeInst);
}

function releasePooledEvent(event) {
  var EventConstructor = this;
  !(event instanceof EventConstructor) ? invariant(false, 'Trying to release an event instance  into a pool of a different type.') : void 0;
  event.destructor();
  if (EventConstructor.eventPool.length < EVENT_POOL_SIZE) {
    EventConstructor.eventPool.push(event);
  }
}

function addEventPoolingTo(EventConstructor) {
  EventConstructor.eventPool = [];
  EventConstructor.getPooled = getPooledEvent;
  EventConstructor.release = releasePooledEvent;
}

var SyntheticEvent$1 = SyntheticEvent;

/**
 * `touchHistory` isn't actually on the native event, but putting it in the
 * interface will ensure that it is cleaned up when pooled/destroyed. The
 * `ResponderEventPlugin` will populate it appropriately.
 */
var ResponderSyntheticEvent = SyntheticEvent$1.extend({
  touchHistory: function (nativeEvent) {
    return null; // Actually doesn't even look at the native event.
  }
});

// Note: ideally these would be imported from DOMTopLevelEventTypes,
// but our build system currently doesn't let us do that from a fork.

var TOP_TOUCH_START = 'touchstart';
var TOP_TOUCH_MOVE = 'touchmove';
var TOP_TOUCH_END = 'touchend';
var TOP_TOUCH_CANCEL = 'touchcancel';
var TOP_SCROLL = 'scroll';
var TOP_SELECTION_CHANGE = 'selectionchange';
var TOP_MOUSE_DOWN = 'mousedown';
var TOP_MOUSE_MOVE = 'mousemove';
var TOP_MOUSE_UP = 'mouseup';

function isStartish(topLevelType) {
  return topLevelType === TOP_TOUCH_START || topLevelType === TOP_MOUSE_DOWN;
}

function isMoveish(topLevelType) {
  return topLevelType === TOP_TOUCH_MOVE || topLevelType === TOP_MOUSE_MOVE;
}

function isEndish(topLevelType) {
  return topLevelType === TOP_TOUCH_END || topLevelType === TOP_TOUCH_CANCEL || topLevelType === TOP_MOUSE_UP;
}

var startDependencies = [TOP_TOUCH_START, TOP_MOUSE_DOWN];
var moveDependencies = [TOP_TOUCH_MOVE, TOP_MOUSE_MOVE];
var endDependencies = [TOP_TOUCH_CANCEL, TOP_TOUCH_END, TOP_MOUSE_UP];

/**
 * Tracks the position and time of each active touch by `touch.identifier`. We
 * should typically only see IDs in the range of 1-20 because IDs get recycled
 * when touches end and start again.
 */


var MAX_TOUCH_BANK = 20;
var touchBank = [];
var touchHistory = {
  touchBank: touchBank,
  numberActiveTouches: 0,
  // If there is only one active touch, we remember its location. This prevents
  // us having to loop through all of the touches all the time in the most
  // common case.
  indexOfSingleActiveTouch: -1,
  mostRecentTimeStamp: 0
};

function timestampForTouch(touch) {
  // The legacy internal implementation provides "timeStamp", which has been
  // renamed to "timestamp". Let both work for now while we iron it out
  // TODO (evv): rename timeStamp to timestamp in internal code
  return touch.timeStamp || touch.timestamp;
}

/**
 * TODO: Instead of making gestures recompute filtered velocity, we could
 * include a built in velocity computation that can be reused globally.
 */
function createTouchRecord(touch) {
  return {
    touchActive: true,
    startPageX: touch.pageX,
    startPageY: touch.pageY,
    startTimeStamp: timestampForTouch(touch),
    currentPageX: touch.pageX,
    currentPageY: touch.pageY,
    currentTimeStamp: timestampForTouch(touch),
    previousPageX: touch.pageX,
    previousPageY: touch.pageY,
    previousTimeStamp: timestampForTouch(touch)
  };
}

function resetTouchRecord(touchRecord, touch) {
  touchRecord.touchActive = true;
  touchRecord.startPageX = touch.pageX;
  touchRecord.startPageY = touch.pageY;
  touchRecord.startTimeStamp = timestampForTouch(touch);
  touchRecord.currentPageX = touch.pageX;
  touchRecord.currentPageY = touch.pageY;
  touchRecord.currentTimeStamp = timestampForTouch(touch);
  touchRecord.previousPageX = touch.pageX;
  touchRecord.previousPageY = touch.pageY;
  touchRecord.previousTimeStamp = timestampForTouch(touch);
}

function getTouchIdentifier(_ref) {
  var identifier = _ref.identifier;

  !(identifier != null) ? invariant(false, 'Touch object is missing identifier.') : void 0;
  {
    !(identifier <= MAX_TOUCH_BANK) ? warning(false, 'Touch identifier %s is greater than maximum supported %s which causes ' + 'performance issues backfilling array locations for all of the indices.', identifier, MAX_TOUCH_BANK) : void 0;
  }
  return identifier;
}

function recordTouchStart(touch) {
  var identifier = getTouchIdentifier(touch);
  var touchRecord = touchBank[identifier];
  if (touchRecord) {
    resetTouchRecord(touchRecord, touch);
  } else {
    touchBank[identifier] = createTouchRecord(touch);
  }
  touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
}

function recordTouchMove(touch) {
  var touchRecord = touchBank[getTouchIdentifier(touch)];
  if (touchRecord) {
    touchRecord.touchActive = true;
    touchRecord.previousPageX = touchRecord.currentPageX;
    touchRecord.previousPageY = touchRecord.currentPageY;
    touchRecord.previousTimeStamp = touchRecord.currentTimeStamp;
    touchRecord.currentPageX = touch.pageX;
    touchRecord.currentPageY = touch.pageY;
    touchRecord.currentTimeStamp = timestampForTouch(touch);
    touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
  } else {
    console.error('Cannot record touch move without a touch start.\n' + 'Touch Move: %s\n', 'Touch Bank: %s', printTouch(touch), printTouchBank());
  }
}

function recordTouchEnd(touch) {
  var touchRecord = touchBank[getTouchIdentifier(touch)];
  if (touchRecord) {
    touchRecord.touchActive = false;
    touchRecord.previousPageX = touchRecord.currentPageX;
    touchRecord.previousPageY = touchRecord.currentPageY;
    touchRecord.previousTimeStamp = touchRecord.currentTimeStamp;
    touchRecord.currentPageX = touch.pageX;
    touchRecord.currentPageY = touch.pageY;
    touchRecord.currentTimeStamp = timestampForTouch(touch);
    touchHistory.mostRecentTimeStamp = timestampForTouch(touch);
  } else {
    console.error('Cannot record touch end without a touch start.\n' + 'Touch End: %s\n', 'Touch Bank: %s', printTouch(touch), printTouchBank());
  }
}

function printTouch(touch) {
  return JSON.stringify({
    identifier: touch.identifier,
    pageX: touch.pageX,
    pageY: touch.pageY,
    timestamp: timestampForTouch(touch)
  });
}

function printTouchBank() {
  var printed = JSON.stringify(touchBank.slice(0, MAX_TOUCH_BANK));
  if (touchBank.length > MAX_TOUCH_BANK) {
    printed += ' (original size: ' + touchBank.length + ')';
  }
  return printed;
}

var ResponderTouchHistoryStore = {
  recordTouchTrack: function (topLevelType, nativeEvent) {
    if (isMoveish(topLevelType)) {
      nativeEvent.changedTouches.forEach(recordTouchMove);
    } else if (isStartish(topLevelType)) {
      nativeEvent.changedTouches.forEach(recordTouchStart);
      touchHistory.numberActiveTouches = nativeEvent.touches.length;
      if (touchHistory.numberActiveTouches === 1) {
        touchHistory.indexOfSingleActiveTouch = nativeEvent.touches[0].identifier;
      }
    } else if (isEndish(topLevelType)) {
      nativeEvent.changedTouches.forEach(recordTouchEnd);
      touchHistory.numberActiveTouches = nativeEvent.touches.length;
      if (touchHistory.numberActiveTouches === 1) {
        for (var i = 0; i < touchBank.length; i++) {
          var touchTrackToCheck = touchBank[i];
          if (touchTrackToCheck != null && touchTrackToCheck.touchActive) {
            touchHistory.indexOfSingleActiveTouch = i;
            break;
          }
        }
        {
          var activeRecord = touchBank[touchHistory.indexOfSingleActiveTouch];
          !(activeRecord != null && activeRecord.touchActive) ? warning(false, 'Cannot find single active touch.') : void 0;
        }
      }
    }
  },


  touchHistory: touchHistory
};

/**
 * Accumulates items that must not be null or undefined.
 *
 * This is used to conserve memory by avoiding array allocations.
 *
 * @return {*|array<*>} An accumulation of items.
 */
function accumulate(current, next) {
  !(next != null) ? invariant(false, 'accumulate(...): Accumulated items must be not be null or undefined.') : void 0;

  if (current == null) {
    return next;
  }

  // Both are not empty. Warning: Never call x.concat(y) when you are not
  // certain that x is an Array (x could be a string with concat method).
  if (Array.isArray(current)) {
    return current.concat(next);
  }

  if (Array.isArray(next)) {
    return [current].concat(next);
  }

  return [current, next];
}

/**
 * Instance of element that should respond to touch/move types of interactions,
 * as indicated explicitly by relevant callbacks.
 */
var responderInst = null;

/**
 * Count of current touches. A textInput should become responder iff the
 * selection changes while there is a touch on the screen.
 */
var trackedTouchCount = 0;

var changeResponder = function (nextResponderInst, blockHostResponder) {
  var oldResponderInst = responderInst;
  responderInst = nextResponderInst;
  if (ResponderEventPlugin.GlobalResponderHandler !== null) {
    ResponderEventPlugin.GlobalResponderHandler.onChange(oldResponderInst, nextResponderInst, blockHostResponder);
  }
};

var eventTypes = {
  /**
   * On a `touchStart`/`mouseDown`, is it desired that this element become the
   * responder?
   */
  startShouldSetResponder: {
    phasedRegistrationNames: {
      bubbled: 'onStartShouldSetResponder',
      captured: 'onStartShouldSetResponderCapture'
    },
    dependencies: startDependencies
  },

  /**
   * On a `scroll`, is it desired that this element become the responder? This
   * is usually not needed, but should be used to retroactively infer that a
   * `touchStart` had occurred during momentum scroll. During a momentum scroll,
   * a touch start will be immediately followed by a scroll event if the view is
   * currently scrolling.
   *
   * TODO: This shouldn't bubble.
   */
  scrollShouldSetResponder: {
    phasedRegistrationNames: {
      bubbled: 'onScrollShouldSetResponder',
      captured: 'onScrollShouldSetResponderCapture'
    },
    dependencies: [TOP_SCROLL]
  },

  /**
   * On text selection change, should this element become the responder? This
   * is needed for text inputs or other views with native selection, so the
   * JS view can claim the responder.
   *
   * TODO: This shouldn't bubble.
   */
  selectionChangeShouldSetResponder: {
    phasedRegistrationNames: {
      bubbled: 'onSelectionChangeShouldSetResponder',
      captured: 'onSelectionChangeShouldSetResponderCapture'
    },
    dependencies: [TOP_SELECTION_CHANGE]
  },

  /**
   * On a `touchMove`/`mouseMove`, is it desired that this element become the
   * responder?
   */
  moveShouldSetResponder: {
    phasedRegistrationNames: {
      bubbled: 'onMoveShouldSetResponder',
      captured: 'onMoveShouldSetResponderCapture'
    },
    dependencies: moveDependencies
  },

  /**
   * Direct responder events dispatched directly to responder. Do not bubble.
   */
  responderStart: {
    registrationName: 'onResponderStart',
    dependencies: startDependencies
  },
  responderMove: {
    registrationName: 'onResponderMove',
    dependencies: moveDependencies
  },
  responderEnd: {
    registrationName: 'onResponderEnd',
    dependencies: endDependencies
  },
  responderRelease: {
    registrationName: 'onResponderRelease',
    dependencies: endDependencies
  },
  responderTerminationRequest: {
    registrationName: 'onResponderTerminationRequest',
    dependencies: []
  },
  responderGrant: {
    registrationName: 'onResponderGrant',
    dependencies: []
  },
  responderReject: {
    registrationName: 'onResponderReject',
    dependencies: []
  },
  responderTerminate: {
    registrationName: 'onResponderTerminate',
    dependencies: []
  }
};

/**
 *
 * Responder System:
 * ----------------
 *
 * - A global, solitary "interaction lock" on a view.
 * - If a node becomes the responder, it should convey visual feedback
 *   immediately to indicate so, either by highlighting or moving accordingly.
 * - To be the responder means, that touches are exclusively important to that
 *   responder view, and no other view.
 * - While touches are still occurring, the responder lock can be transferred to
 *   a new view, but only to increasingly "higher" views (meaning ancestors of
 *   the current responder).
 *
 * Responder being granted:
 * ------------------------
 *
 * - Touch starts, moves, and scrolls can cause an ID to become the responder.
 * - We capture/bubble `startShouldSetResponder`/`moveShouldSetResponder` to
 *   the "appropriate place".
 * - If nothing is currently the responder, the "appropriate place" is the
 *   initiating event's `targetID`.
 * - If something *is* already the responder, the "appropriate place" is the
 *   first common ancestor of the event target and the current `responderInst`.
 * - Some negotiation happens: See the timing diagram below.
 * - Scrolled views automatically become responder. The reasoning is that a
 *   platform scroll view that isn't built on top of the responder system has
 *   began scrolling, and the active responder must now be notified that the
 *   interaction is no longer locked to it - the system has taken over.
 *
 * - Responder being released:
 *   As soon as no more touches that *started* inside of descendants of the
 *   *current* responderInst, an `onResponderRelease` event is dispatched to the
 *   current responder, and the responder lock is released.
 *
 * TODO:
 * - on "end", a callback hook for `onResponderEndShouldRemainResponder` that
 *   determines if the responder lock should remain.
 * - If a view shouldn't "remain" the responder, any active touches should by
 *   default be considered "dead" and do not influence future negotiations or
 *   bubble paths. It should be as if those touches do not exist.
 * -- For multitouch: Usually a translate-z will choose to "remain" responder
 *  after one out of many touches ended. For translate-y, usually the view
 *  doesn't wish to "remain" responder after one of many touches end.
 * - Consider building this on top of a `stopPropagation` model similar to
 *   `W3C` events.
 * - Ensure that `onResponderTerminate` is called on touch cancels, whether or
 *   not `onResponderTerminationRequest` returns `true` or `false`.
 *
 */

/*                                             Negotiation Performed
                                             +-----------------------+
                                            /                         \
Process low level events to    +     Current Responder      +   wantsResponderID
determine who to perform negot-|   (if any exists at all)   |
iation/transition              | Otherwise just pass through|
-------------------------------+----------------------------+------------------+
Bubble to find first ID        |                            |
to return true:wantsResponderID|                            |
                               |                            |
     +-------------+           |                            |
     | onTouchStart|           |                            |
     +------+------+     none  |                            |
            |            return|                            |
+-----------v-------------+true| +------------------------+ |
|onStartShouldSetResponder|----->|onResponderStart (cur)  |<-----------+
+-----------+-------------+    | +------------------------+ |          |
            |                  |                            | +--------+-------+
            | returned true for|       false:REJECT +-------->|onResponderReject
            | wantsResponderID |                    |       | +----------------+
            | (now attempt     | +------------------+-----+ |
            |  handoff)        | |   onResponder          | |
            +------------------->|      TerminationRequest| |
                               | +------------------+-----+ |
                               |                    |       | +----------------+
                               |         true:GRANT +-------->|onResponderGrant|
                               |                            | +--------+-------+
                               | +------------------------+ |          |
                               | |   onResponderTerminate |<-----------+
                               | +------------------+-----+ |
                               |                    |       | +----------------+
                               |                    +-------->|onResponderStart|
                               |                            | +----------------+
Bubble to find first ID        |                            |
to return true:wantsResponderID|                            |
                               |                            |
     +-------------+           |                            |
     | onTouchMove |           |                            |
     +------+------+     none  |                            |
            |            return|                            |
+-----------v-------------+true| +------------------------+ |
|onMoveShouldSetResponder |----->|onResponderMove (cur)   |<-----------+
+-----------+-------------+    | +------------------------+ |          |
            |                  |                            | +--------+-------+
            | returned true for|       false:REJECT +-------->|onResponderRejec|
            | wantsResponderID |                    |       | +----------------+
            | (now attempt     | +------------------+-----+ |
            |  handoff)        | |   onResponder          | |
            +------------------->|      TerminationRequest| |
                               | +------------------+-----+ |
                               |                    |       | +----------------+
                               |         true:GRANT +-------->|onResponderGrant|
                               |                            | +--------+-------+
                               | +------------------------+ |          |
                               | |   onResponderTerminate |<-----------+
                               | +------------------+-----+ |
                               |                    |       | +----------------+
                               |                    +-------->|onResponderMove |
                               |                            | +----------------+
                               |                            |
                               |                            |
      Some active touch started|                            |
      inside current responder | +------------------------+ |
      +------------------------->|      onResponderEnd    | |
      |                        | +------------------------+ |
  +---+---------+              |                            |
  | onTouchEnd  |              |                            |
  +---+---------+              |                            |
      |                        | +------------------------+ |
      +------------------------->|     onResponderEnd     | |
      No active touches started| +-----------+------------+ |
      inside current responder |             |              |
                               |             v              |
                               | +------------------------+ |
                               | |    onResponderRelease  | |
                               | +------------------------+ |
                               |                            |
                               +                            + */

/**
 * A note about event ordering in the `EventPluginHub`.
 *
 * Suppose plugins are injected in the following order:
 *
 * `[R, S, C]`
 *
 * To help illustrate the example, assume `S` is `SimpleEventPlugin` (for
 * `onClick` etc) and `R` is `ResponderEventPlugin`.
 *
 * "Deferred-Dispatched Events":
 *
 * - The current event plugin system will traverse the list of injected plugins,
 *   in order, and extract events by collecting the plugin's return value of
 *   `extractEvents()`.
 * - These events that are returned from `extractEvents` are "deferred
 *   dispatched events".
 * - When returned from `extractEvents`, deferred-dispatched events contain an
 *   "accumulation" of deferred dispatches.
 * - These deferred dispatches are accumulated/collected before they are
 *   returned, but processed at a later time by the `EventPluginHub` (hence the
 *   name deferred).
 *
 * In the process of returning their deferred-dispatched events, event plugins
 * themselves can dispatch events on-demand without returning them from
 * `extractEvents`. Plugins might want to do this, so that they can use event
 * dispatching as a tool that helps them decide which events should be extracted
 * in the first place.
 *
 * "On-Demand-Dispatched Events":
 *
 * - On-demand-dispatched events are not returned from `extractEvents`.
 * - On-demand-dispatched events are dispatched during the process of returning
 *   the deferred-dispatched events.
 * - They should not have side effects.
 * - They should be avoided, and/or eventually be replaced with another
 *   abstraction that allows event plugins to perform multiple "rounds" of event
 *   extraction.
 *
 * Therefore, the sequence of event dispatches becomes:
 *
 * - `R`s on-demand events (if any)   (dispatched by `R` on-demand)
 * - `S`s on-demand events (if any)   (dispatched by `S` on-demand)
 * - `C`s on-demand events (if any)   (dispatched by `C` on-demand)
 * - `R`s extracted events (if any)   (dispatched by `EventPluginHub`)
 * - `S`s extracted events (if any)   (dispatched by `EventPluginHub`)
 * - `C`s extracted events (if any)   (dispatched by `EventPluginHub`)
 *
 * In the case of `ResponderEventPlugin`: If the `startShouldSetResponder`
 * on-demand dispatch returns `true` (and some other details are satisfied) the
 * `onResponderGrant` deferred dispatched event is returned from
 * `extractEvents`. The sequence of dispatch executions in this case
 * will appear as follows:
 *
 * - `startShouldSetResponder` (`ResponderEventPlugin` dispatches on-demand)
 * - `touchStartCapture`       (`EventPluginHub` dispatches as usual)
 * - `touchStart`              (`EventPluginHub` dispatches as usual)
 * - `responderGrant/Reject`   (`EventPluginHub` dispatches as usual)
 */

function setResponderAndExtractTransfer(topLevelType, targetInst, nativeEvent, nativeEventTarget) {
  var shouldSetEventType = isStartish(topLevelType) ? eventTypes.startShouldSetResponder : isMoveish(topLevelType) ? eventTypes.moveShouldSetResponder : topLevelType === TOP_SELECTION_CHANGE ? eventTypes.selectionChangeShouldSetResponder : eventTypes.scrollShouldSetResponder;

  // TODO: stop one short of the current responder.
  var bubbleShouldSetFrom = !responderInst ? targetInst : getLowestCommonAncestor(responderInst, targetInst);

  // When capturing/bubbling the "shouldSet" event, we want to skip the target
  // (deepest ID) if it happens to be the current responder. The reasoning:
  // It's strange to get an `onMoveShouldSetResponder` when you're *already*
  // the responder.
  var skipOverBubbleShouldSetFrom = bubbleShouldSetFrom === responderInst;
  var shouldSetEvent = ResponderSyntheticEvent.getPooled(shouldSetEventType, bubbleShouldSetFrom, nativeEvent, nativeEventTarget);
  shouldSetEvent.touchHistory = ResponderTouchHistoryStore.touchHistory;
  if (skipOverBubbleShouldSetFrom) {
    accumulateTwoPhaseDispatchesSkipTarget(shouldSetEvent);
  } else {
    accumulateTwoPhaseDispatches(shouldSetEvent);
  }
  var wantsResponderInst = executeDispatchesInOrderStopAtTrue(shouldSetEvent);
  if (!shouldSetEvent.isPersistent()) {
    shouldSetEvent.constructor.release(shouldSetEvent);
  }

  if (!wantsResponderInst || wantsResponderInst === responderInst) {
    return null;
  }
  var extracted = void 0;
  var grantEvent = ResponderSyntheticEvent.getPooled(eventTypes.responderGrant, wantsResponderInst, nativeEvent, nativeEventTarget);
  grantEvent.touchHistory = ResponderTouchHistoryStore.touchHistory;

  accumulateDirectDispatches(grantEvent);
  var blockHostResponder = executeDirectDispatch(grantEvent) === true;
  if (responderInst) {
    var terminationRequestEvent = ResponderSyntheticEvent.getPooled(eventTypes.responderTerminationRequest, responderInst, nativeEvent, nativeEventTarget);
    terminationRequestEvent.touchHistory = ResponderTouchHistoryStore.touchHistory;
    accumulateDirectDispatches(terminationRequestEvent);
    var shouldSwitch = !hasDispatches(terminationRequestEvent) || executeDirectDispatch(terminationRequestEvent);
    if (!terminationRequestEvent.isPersistent()) {
      terminationRequestEvent.constructor.release(terminationRequestEvent);
    }

    if (shouldSwitch) {
      var terminateEvent = ResponderSyntheticEvent.getPooled(eventTypes.responderTerminate, responderInst, nativeEvent, nativeEventTarget);
      terminateEvent.touchHistory = ResponderTouchHistoryStore.touchHistory;
      accumulateDirectDispatches(terminateEvent);
      extracted = accumulate(extracted, [grantEvent, terminateEvent]);
      changeResponder(wantsResponderInst, blockHostResponder);
    } else {
      var rejectEvent = ResponderSyntheticEvent.getPooled(eventTypes.responderReject, wantsResponderInst, nativeEvent, nativeEventTarget);
      rejectEvent.touchHistory = ResponderTouchHistoryStore.touchHistory;
      accumulateDirectDispatches(rejectEvent);
      extracted = accumulate(extracted, rejectEvent);
    }
  } else {
    extracted = accumulate(extracted, grantEvent);
    changeResponder(wantsResponderInst, blockHostResponder);
  }
  return extracted;
}

/**
 * A transfer is a negotiation between a currently set responder and the next
 * element to claim responder status. Any start event could trigger a transfer
 * of responderInst. Any move event could trigger a transfer.
 *
 * @param {string} topLevelType Record from `BrowserEventConstants`.
 * @return {boolean} True if a transfer of responder could possibly occur.
 */
function canTriggerTransfer(topLevelType, topLevelInst, nativeEvent) {
  return topLevelInst && (
  // responderIgnoreScroll: We are trying to migrate away from specifically
  // tracking native scroll events here and responderIgnoreScroll indicates we
  // will send topTouchCancel to handle canceling touch events instead
  topLevelType === TOP_SCROLL && !nativeEvent.responderIgnoreScroll || trackedTouchCount > 0 && topLevelType === TOP_SELECTION_CHANGE || isStartish(topLevelType) || isMoveish(topLevelType));
}

/**
 * Returns whether or not this touch end event makes it such that there are no
 * longer any touches that started inside of the current `responderInst`.
 *
 * @param {NativeEvent} nativeEvent Native touch end event.
 * @return {boolean} Whether or not this touch end event ends the responder.
 */
function noResponderTouches(nativeEvent) {
  var touches = nativeEvent.touches;
  if (!touches || touches.length === 0) {
    return true;
  }
  for (var i = 0; i < touches.length; i++) {
    var activeTouch = touches[i];
    var target = activeTouch.target;
    if (target !== null && target !== undefined && target !== 0) {
      // Is the original touch location inside of the current responder?
      var targetInst = getInstanceFromNode(target);
      if (isAncestor(responderInst, targetInst)) {
        return false;
      }
    }
  }
  return true;
}

var ResponderEventPlugin = {
  /* For unit testing only */
  _getResponder: function () {
    return responderInst;
  },

  eventTypes: eventTypes,

  /**
   * We must be resilient to `targetInst` being `null` on `touchMove` or
   * `touchEnd`. On certain platforms, this means that a native scroll has
   * assumed control and the original touch targets are destroyed.
   */
  extractEvents: function (topLevelType, targetInst, nativeEvent, nativeEventTarget) {
    if (isStartish(topLevelType)) {
      trackedTouchCount += 1;
    } else if (isEndish(topLevelType)) {
      if (trackedTouchCount >= 0) {
        trackedTouchCount -= 1;
      } else {
        console.error('Ended a touch event which was not counted in `trackedTouchCount`.');
        return null;
      }
    }

    ResponderTouchHistoryStore.recordTouchTrack(topLevelType, nativeEvent);

    var extracted = canTriggerTransfer(topLevelType, targetInst, nativeEvent) ? setResponderAndExtractTransfer(topLevelType, targetInst, nativeEvent, nativeEventTarget) : null;
    // Responder may or may not have transferred on a new touch start/move.
    // Regardless, whoever is the responder after any potential transfer, we
    // direct all touch start/move/ends to them in the form of
    // `onResponderMove/Start/End`. These will be called for *every* additional
    // finger that move/start/end, dispatched directly to whoever is the
    // current responder at that moment, until the responder is "released".
    //
    // These multiple individual change touch events are are always bookended
    // by `onResponderGrant`, and one of
    // (`onResponderRelease/onResponderTerminate`).
    var isResponderTouchStart = responderInst && isStartish(topLevelType);
    var isResponderTouchMove = responderInst && isMoveish(topLevelType);
    var isResponderTouchEnd = responderInst && isEndish(topLevelType);
    var incrementalTouch = isResponderTouchStart ? eventTypes.responderStart : isResponderTouchMove ? eventTypes.responderMove : isResponderTouchEnd ? eventTypes.responderEnd : null;

    if (incrementalTouch) {
      var gesture = ResponderSyntheticEvent.getPooled(incrementalTouch, responderInst, nativeEvent, nativeEventTarget);
      gesture.touchHistory = ResponderTouchHistoryStore.touchHistory;
      accumulateDirectDispatches(gesture);
      extracted = accumulate(extracted, gesture);
    }

    var isResponderTerminate = responderInst && topLevelType === TOP_TOUCH_CANCEL;
    var isResponderRelease = responderInst && !isResponderTerminate && isEndish(topLevelType) && noResponderTouches(nativeEvent);
    var finalTouch = isResponderTerminate ? eventTypes.responderTerminate : isResponderRelease ? eventTypes.responderRelease : null;
    if (finalTouch) {
      var finalEvent = ResponderSyntheticEvent.getPooled(finalTouch, responderInst, nativeEvent, nativeEventTarget);
      finalEvent.touchHistory = ResponderTouchHistoryStore.touchHistory;
      accumulateDirectDispatches(finalEvent);
      extracted = accumulate(extracted, finalEvent);
      changeResponder(null);
    }

    return extracted;
  },

  GlobalResponderHandler: null,

  injection: {
    /**
     * @param {{onChange: (ReactID, ReactID) => void} GlobalResponderHandler
     * Object that handles any change in responder. Use this to inject
     * integration with an existing touch handling system etc.
     */
    injectGlobalResponderHandler: function (GlobalResponderHandler) {
      ResponderEventPlugin.GlobalResponderHandler = GlobalResponderHandler;
    }
  }
};

// This is used by react-native-web.
var injectComponentTree = injection.injectComponentTree;
// Inject react-dom's ComponentTree into this module.
var ReactDOMComponentTree = ReactDOM.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED.ReactDOMComponentTree;

injectComponentTree(ReactDOMComponentTree);

var ReactDOMUnstableNativeDependencies = Object.freeze({
	injectComponentTree: injectComponentTree,
	ResponderEventPlugin: ResponderEventPlugin,
	ResponderTouchHistoryStore: ResponderTouchHistoryStore
});

var unstableNativeDependencies = ReactDOMUnstableNativeDependencies;

module.exports = unstableNativeDependencies;
  })();
}