/**
 * Copyright 2013 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @providesModule EventPluginRegistry
 * @typechecks static-only
 */

"use strict";

var invariant = require('invariant');

/**
 * Injectable ordering of event plugins.
 */
var EventPluginOrder = null;

/**
 * Injectable mapping from names to event plugin modules.
 */
var namesToPlugins = {};

/**
 * Recomputes the plugin list using the injected plugins and plugin ordering.
 *
 * @private
 */
function recomputePluginOrdering() {
  if (!EventPluginOrder) {
    // Wait until an `EventPluginOrder` is injected.
    return;
  }
  for (var pluginName in namesToPlugins) {
    var PluginModule = namesToPlugins[pluginName];
    var pluginIndex = EventPluginOrder.indexOf(pluginName);
    invariant(
      pluginIndex > -1,
      'EventPluginRegistry: Cannot inject event plugins that do not exist in ' +
      'the plugin ordering, `%s`.',
      pluginName
    );
    if (EventPluginRegistry.plugins[pluginIndex]) {
      continue;
    }
    invariant(
      PluginModule.extractEvents,
      'EventPluginRegistry: Event plugins must implement an `extractEvents` ' +
      'method, but `%s` does not.',
      pluginName
    );
    EventPluginRegistry.plugins[pluginIndex] = PluginModule;
    var publishedEvents = PluginModule.eventTypes;
    for (var eventName in publishedEvents) {
      invariant(
        publishEventForPlugin(publishedEvents[eventName], PluginModule, eventName),
        'EventPluginRegistry: Failed to publish event `%s` for plugin `%s`.',
        eventName,
        pluginName
      );
    }
  }
}

/**
 * Publishes an event so that it can be dispatched by the supplied plugin.
 *
 * @param {object} dispatchConfig Dispatch configuration for the event.
 * @param {object} PluginModule Plugin publishing the event.
 * @return {boolean} True if the event was successfully published.
 * @private
 */
function publishEventForPlugin(dispatchConfig, PluginModule, eventName) {
  var phasedRegistrationNames = dispatchConfig.phasedRegistrationNames;
  if (phasedRegistrationNames) {
    for (var phaseName in phasedRegistrationNames) {
      if (phasedRegistrationNames.hasOwnProperty(phaseName)) {
        var phasedRegistrationName = phasedRegistrationNames[phaseName];
        publishRegistrationName(phasedRegistrationName, PluginModule, eventName);
      }
    }
    return true;
  } else if (dispatchConfig.registrationName) {
    publishRegistrationName(dispatchConfig.registrationName, PluginModule, eventName);
    return true;
  }
  return false;
}

/**
 * Publishes a registration name that is used to identify dispatched events and
 * can be used with `EventPluginHub.putListener` to register listeners.
 *
 * @param {string} registrationName Registration name to add.
 * @param {object} PluginModule Plugin publishing the event.
 * @private
 */
function publishRegistrationName(registrationName, PluginModule, eventName) {
  invariant(
    !EventPluginRegistry.registrationNameModules[registrationName],
    'EventPluginHub: More than one plugin attempted to publish the same ' +
    'registration name, `%s`.',
    registrationName
  );
  EventPluginRegistry.registrationNameModules[registrationName] = PluginModule;
  EventPluginRegistry.registrationNameDependencies[registrationName] =
    PluginModule.eventTypes[eventName].dependencies;
}

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

  /**
   * Ordered list of injected plugins.
   */
  plugins: [],

  /**
   * Mapping from registration names to plugin modules.
   */
  registrationNameModules: {},

  /**
   * Mapping from registration name to event name
   */
  registrationNameDependencies: {},

  /**
   * 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}
   */
  injectEventPluginOrder: function(InjectedEventPluginOrder) {
    invariant(
      !EventPluginOrder,
      'EventPluginRegistry: Cannot inject event plugin ordering more than once.'
    );
    // Clone the ordering so it cannot be dynamically mutated.
    EventPluginOrder = Array.prototype.slice.call(InjectedEventPluginOrder);
    recomputePluginOrdering();
  },

  /**
   * 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}
   */
  injectEventPluginsByName: function(injectedNamesToPlugins) {
    var isOrderingDirty = false;
    for (var pluginName in injectedNamesToPlugins) {
      if (!injectedNamesToPlugins.hasOwnProperty(pluginName)) {
        continue;
      }
      var PluginModule = injectedNamesToPlugins[pluginName];
      if (namesToPlugins[pluginName] !== PluginModule) {
        invariant(
          !namesToPlugins[pluginName],
          'EventPluginRegistry: Cannot inject two different event plugins ' +
          'using the same name, `%s`.',
          pluginName
        );
        namesToPlugins[pluginName] = PluginModule;
        isOrderingDirty = true;
      }
    }
    if (isOrderingDirty) {
      recomputePluginOrdering();
    }
  },

  /**
   * Looks up the plugin for the supplied event.
   *
   * @param {object} event A synthetic event.
   * @return {?object} The plugin that created the supplied event.
   * @internal
   */
  getPluginModuleForEvent: function(event) {
    var dispatchConfig = event.dispatchConfig;
    if (dispatchConfig.registrationName) {
      return EventPluginRegistry.registrationNameModules[
        dispatchConfig.registrationName
      ] || null;
    }
    for (var phase in dispatchConfig.phasedRegistrationNames) {
      if (!dispatchConfig.phasedRegistrationNames.hasOwnProperty(phase)) {
        continue;
      }
      var PluginModule = EventPluginRegistry.registrationNameModules[
        dispatchConfig.phasedRegistrationNames[phase]
      ];
      if (PluginModule) {
        return PluginModule;
      }
    }
    return null;
  },

  /**
   * Exposed for unit testing.
   * @private
   */
  _resetEventPlugins: function() {
    EventPluginOrder = null;
    for (var pluginName in namesToPlugins) {
      if (namesToPlugins.hasOwnProperty(pluginName)) {
        delete namesToPlugins[pluginName];
      }
    }
    EventPluginRegistry.plugins.length = 0;
    var registrationNameModules = EventPluginRegistry.registrationNameModules;
    for (var registrationName in registrationNameModules) {
      if (registrationNameModules.hasOwnProperty(registrationName)) {
        delete registrationNameModules[registrationName];
      }
    }
  }

};

module.exports = EventPluginRegistry;
