/**
 * @file
 * A Backbone Model for the state of an in-place editable entity in the DOM.
 */

(function (_, $, Backbone, Drupal) {
  Drupal.quickedit.EntityModel = Drupal.quickedit.BaseModel.extend(/** @lends Drupal.quickedit.EntityModel# */{

    /**
     * @type {object}
     */
    defaults: /** @lends Drupal.quickedit.EntityModel# */{

      /**
       * The DOM element that represents this entity.
       *
       * It may seem bizarre to have a DOM element in a Backbone Model, but we
       * need to be able to map entities in the DOM to EntityModels in memory.
       *
       * @type {HTMLElement}
       */
      el: null,

      /**
       * An entity ID, of the form `<entity type>/<entity ID>`
       *
       * @example
       * "node/1"
       *
       * @type {string}
       */
      entityID: null,

      /**
       * An entity instance ID.
       *
       * The first instance of a specific entity (i.e. with a given entity ID)
       * is assigned 0, the second 1, and so on.
       *
       * @type {number}
       */
      entityInstanceID: null,

      /**
       * The unique ID of this entity instance on the page, of the form
       * `<entity type>/<entity ID>[entity instance ID]`
       *
       * @example
       * "node/1[0]"
       *
       * @type {string}
       */
      id: null,

      /**
       * The label of the entity.
       *
       * @type {string}
       */
      label: null,

      /**
       * A FieldCollection for all fields of the entity.
       *
       * @type {Drupal.quickedit.FieldCollection}
       *
       * @see Drupal.quickedit.FieldCollection
       */
      fields: null,

      // The attributes below are stateful. The ones above will never change
      // during the life of a EntityModel instance.

      /**
       * Indicates whether this entity is currently being edited in-place.
       *
       * @type {bool}
       */
      isActive: false,

      /**
       * Whether one or more fields are already been stored in PrivateTempStore.
       *
       * @type {bool}
       */
      inTempStore: false,

      /**
       * Indicates whether a "Save" button is necessary or not.
       *
       * Whether one or more fields have already been stored in PrivateTempStore
       * *or* the field that's currently being edited is in the 'changed' or a
       * later state.
       *
       * @type {bool}
       */
      isDirty: false,

      /**
       * Whether the request to the server has been made to commit this entity.
       *
       * Used to prevent multiple such requests.
       *
       * @type {bool}
       */
      isCommitting: false,

      /**
       * The current processing state of an entity.
       *
       * @type {string}
       */
      state: 'closed',

      /**
       * IDs of fields whose new values have been stored in PrivateTempStore.
       *
       * We must store this on the EntityModel as well (even though it already
       * is on the FieldModel) because when a field is rerendered, its
       * FieldModel is destroyed and this allows us to transition it back to
       * the proper state.
       *
       * @type {Array.<string>}
       */
      fieldsInTempStore: [],

      /**
       * A flag the tells the application that this EntityModel must be reloaded
       * in order to restore the original values to its fields in the client.
       *
       * @type {bool}
       */
      reload: false,
    },

    /**
     * @constructs
     *
     * @augments Drupal.quickedit.BaseModel
     */
    initialize() {
      this.set('fields', new Drupal.quickedit.FieldCollection());

      // Respond to entity state changes.
      this.listenTo(this, 'change:state', this.stateChange);

      // The state of the entity is largely dependent on the state of its
      // fields.
      this.listenTo(this.get('fields'), 'change:state', this.fieldStateChange);

      // Call Drupal.quickedit.BaseModel's initialize() method.
      Drupal.quickedit.BaseModel.prototype.initialize.call(this);
    },

    /**
     * Updates FieldModels' states when an EntityModel change occurs.
     *
     * @param {Drupal.quickedit.EntityModel} entityModel
     *   The entity model
     * @param {string} state
     *   The state of the associated entity. One of
     *   {@link Drupal.quickedit.EntityModel.states}.
     * @param {object} options
     *   Options for the entity model.
     */
    stateChange(entityModel, state, options) {
      const to = state;
      switch (to) {
        case 'closed':
          this.set({
            isActive: false,
            inTempStore: false,
            isDirty: false,
          });
          break;

        case 'launching':
          break;

        case 'opening':
          // Set the fields to candidate state.
          entityModel.get('fields').each((fieldModel) => {
            fieldModel.set('state', 'candidate', options);
          });
          break;

        case 'opened':
          // The entity is now ready for editing!
          this.set('isActive', true);
          break;

        case 'committing': {
          // The user indicated they want to save the entity.
          const fields = this.get('fields');
          // For fields that are in an active state, transition them to
          // candidate.
          fields.chain()
            .filter(fieldModel => _.intersection([fieldModel.get('state')], ['active']).length)
            .each((fieldModel) => {
              fieldModel.set('state', 'candidate');
            });
          // For fields that are in a changed state, field values must first be
          // stored in PrivateTempStore.
          fields.chain()
            .filter(fieldModel => _.intersection([fieldModel.get('state')], Drupal.quickedit.app.changedFieldStates).length)
            .each((fieldModel) => {
              fieldModel.set('state', 'saving');
            });
          break;
        }

        case 'deactivating': {
          const changedFields = this.get('fields')
            .filter(fieldModel => _.intersection([fieldModel.get('state')], ['changed', 'invalid']).length);
          // If the entity contains unconfirmed or unsaved changes, return the
          // entity to an opened state and ask the user if they would like to
          // save the changes or discard the changes.
          //   1. One of the fields is in a changed state. The changed field
          //   might just be a change in the client or it might have been saved
          //   to tempstore.
          //   2. The saved flag is empty and the confirmed flag is empty. If
          //   the entity has been saved to the server, the fields changed in
          //   the client are irrelevant. If the changes are confirmed, then
          //   proceed to set the fields to candidate state.
          if ((changedFields.length || this.get('fieldsInTempStore').length) && (!options.saved && !options.confirmed)) {
            // Cancel deactivation until the user confirms save or discard.
            this.set('state', 'opened', { confirming: true });
            // An action in reaction to state change must be deferred.
            _.defer(() => {
              Drupal.quickedit.app.confirmEntityDeactivation(entityModel);
            });
          }
          else {
            const invalidFields = this.get('fields')
              .filter(fieldModel => _.intersection([fieldModel.get('state')], ['invalid']).length);
            // Indicate if this EntityModel needs to be reloaded in order to
            // restore the original values of its fields.
            entityModel.set('reload', (this.get('fieldsInTempStore').length || invalidFields.length));
            // Set all fields to the 'candidate' state. A changed field may have
            // to go through confirmation first.
            entityModel.get('fields').each((fieldModel) => {
              // If the field is already in the candidate state, trigger a
              // change event so that the entityModel can move to the next state
              // in deactivation.
              if (_.intersection([fieldModel.get('state')], ['candidate', 'highlighted']).length) {
                fieldModel.trigger('change:state', fieldModel, fieldModel.get('state'), options);
              }
              else {
                fieldModel.set('state', 'candidate', options);
              }
            });
          }
          break;
        }

        case 'closing':
          // Set all fields to the 'inactive' state.
          options.reason = 'stop';
          this.get('fields').each((fieldModel) => {
            fieldModel.set({
              inTempStore: false,
              state: 'inactive',
            }, options);
          });
          break;
      }
    },

    /**
     * Updates a Field and Entity model's "inTempStore" when appropriate.
     *
     * Helper function.
     *
     * @param {Drupal.quickedit.EntityModel} entityModel
     *   The model of the entity for which a field's state attribute has
     *   changed.
     * @param {Drupal.quickedit.FieldModel} fieldModel
     *   The model of the field whose state attribute has changed.
     *
     * @see Drupal.quickedit.EntityModel#fieldStateChange
     */
    _updateInTempStoreAttributes(entityModel, fieldModel) {
      const current = fieldModel.get('state');
      const previous = fieldModel.previous('state');
      let fieldsInTempStore = entityModel.get('fieldsInTempStore');
      // If the fieldModel changed to the 'saved' state: remember that this
      // field was saved to PrivateTempStore.
      if (current === 'saved') {
        // Mark the entity as saved in PrivateTempStore, so that we can pass the
        // proper "reset PrivateTempStore" boolean value when communicating with
        // the server.
        entityModel.set('inTempStore', true);
        // Mark the field as saved in PrivateTempStore, so that visual
        // indicators signifying just that may be rendered.
        fieldModel.set('inTempStore', true);
        // Remember that this field is in PrivateTempStore, restore when
        // rerendered.
        fieldsInTempStore.push(fieldModel.get('fieldID'));
        fieldsInTempStore = _.uniq(fieldsInTempStore);
        entityModel.set('fieldsInTempStore', fieldsInTempStore);
      }
      // If the fieldModel changed to the 'candidate' state from the
      // 'inactive' state, then this is a field for this entity that got
      // rerendered. Restore its previous 'inTempStore' attribute value.
      else if (current === 'candidate' && previous === 'inactive') {
        fieldModel.set('inTempStore', _.intersection([fieldModel.get('fieldID')], fieldsInTempStore).length > 0);
      }
    },

    /**
     * Reacts to state changes in this entity's fields.
     *
     * @param {Drupal.quickedit.FieldModel} fieldModel
     *   The model of the field whose state attribute changed.
     * @param {string} state
     *   The state of the associated field. One of
     *   {@link Drupal.quickedit.FieldModel.states}.
     */
    fieldStateChange(fieldModel, state) {
      const entityModel = this;
      const fieldState = state;
      // Switch on the entityModel state.
      // The EntityModel responds to FieldModel state changes as a function of
      // its state. For example, a field switching back to 'candidate' state
      // when its entity is in the 'opened' state has no effect on the entity.
      // But that same switch back to 'candidate' state of a field when the
      // entity is in the 'committing' state might allow the entity to proceed
      // with the commit flow.
      switch (this.get('state')) {
        case 'closed':
        case 'launching':
          // It should be impossible to reach these: fields can't change state
          // while the entity is closed or still launching.
          break;

        case 'opening':
          // We must change the entity to the 'opened' state, but it must first
          // be confirmed that all of its fieldModels have transitioned to the
          // 'candidate' state.
          // We do this here, because this is called every time a fieldModel
          // changes state, hence each time this is called, we get closer to the
          // goal of having all fieldModels in the 'candidate' state.
          // A state change in reaction to another state change must be
          // deferred.
          _.defer(() => {
            entityModel.set('state', 'opened', {
              'accept-field-states': Drupal.quickedit.app.readyFieldStates,
            });
          });
          break;

        case 'opened':
          // Set the isDirty attribute when appropriate so that it is known when
          // to display the "Save" button in the entity toolbar.
          // Note that once a field has been changed, there's no way to discard
          // that change, hence it will have to be saved into PrivateTempStore,
          // or the in-place editing of this field will have to be stopped
          // completely. In other words: once any field enters the 'changed'
          // field, then for the remainder of the in-place editing session, the
          // entity is by definition dirty.
          if (fieldState === 'changed') {
            entityModel.set('isDirty', true);
          }
          else {
            this._updateInTempStoreAttributes(entityModel, fieldModel);
          }
          break;

        case 'committing': {
          // If the field save returned a validation error, set the state of the
          // entity back to 'opened'.
          if (fieldState === 'invalid') {
            // A state change in reaction to another state change must be
            // deferred.
            _.defer(() => {
              entityModel.set('state', 'opened', { reason: 'invalid' });
            });
          }
          else {
            this._updateInTempStoreAttributes(entityModel, fieldModel);
          }

          // Attempt to save the entity. If the entity's fields are not yet all
          // in a ready state, the save will not be processed.
          const options = {
            'accept-field-states': Drupal.quickedit.app.readyFieldStates,
          };
          if (entityModel.set('isCommitting', true, options)) {
            entityModel.save({
              success() {
                entityModel.set({
                  state: 'deactivating',
                  isCommitting: false,
                }, { saved: true });
              },
              error() {
                // Reset the "isCommitting" mutex.
                entityModel.set('isCommitting', false);
                // Change the state back to "opened", to allow the user to hit
                // the "Save" button again.
                entityModel.set('state', 'opened', { reason: 'networkerror' });
                // Show a modal to inform the user of the network error.
                const message = Drupal.t('Your changes to <q>@entity-title</q> could not be saved, either due to a website problem or a network connection problem.<br>Please try again.', { '@entity-title': entityModel.get('label') });
                Drupal.quickedit.util.networkErrorModal(Drupal.t('Network problem!'), message);
              },
            });
          }
          break;
        }

        case 'deactivating':
          // When setting the entity to 'closing', require that all fieldModels
          // are in either the 'candidate' or 'highlighted' state.
          // A state change in reaction to another state change must be
          // deferred.
          _.defer(() => {
            entityModel.set('state', 'closing', {
              'accept-field-states': Drupal.quickedit.app.readyFieldStates,
            });
          });
          break;

        case 'closing':
          // When setting the entity to 'closed', require that all fieldModels
          // are in the 'inactive' state.
          // A state change in reaction to another state change must be
          // deferred.
          _.defer(() => {
            entityModel.set('state', 'closed', {
              'accept-field-states': ['inactive'],
            });
          });
          break;
      }
    },

    /**
     * Fires an AJAX request to the REST save URL for an entity.
     *
     * @param {object} options
     *   An object of options that contains:
     * @param {function} [options.success]
     *   A function to invoke if the entity is successfully saved.
     */
    save(options) {
      const entityModel = this;

      // Create a Drupal.ajax instance to save the entity.
      const entitySaverAjax = Drupal.ajax({
        url: Drupal.url(`quickedit/entity/${entityModel.get('entityID')}`),
        error() {
          // Let the Drupal.quickedit.EntityModel Backbone model's error()
          // method handle errors.
          options.error.call(entityModel);
        },
      });
      // Entity saved successfully.
      entitySaverAjax.commands.quickeditEntitySaved = function (ajax, response, status) {
        // All fields have been moved from PrivateTempStore to permanent
        // storage, update the "inTempStore" attribute on FieldModels, on the
        // EntityModel and clear EntityModel's "fieldInTempStore" attribute.
        entityModel.get('fields').each((fieldModel) => {
          fieldModel.set('inTempStore', false);
        });
        entityModel.set('inTempStore', false);
        entityModel.set('fieldsInTempStore', []);

        // Invoke the optional success callback.
        if (options.success) {
          options.success.call(entityModel);
        }
      };
      // Trigger the AJAX request, which will will return the
      // quickeditEntitySaved AJAX command to which we then react.
      entitySaverAjax.execute();
    },

    /**
     * Validate the entity model.
     *
     * @param {object} attrs
     *   The attributes changes in the save or set call.
     * @param {object} options
     *   An object with the following option:
     * @param {string} [options.reason]
     *   A string that conveys a particular reason to allow for an exceptional
     *   state change.
     * @param {Array} options.accept-field-states
     *   An array of strings that represent field states that the entities must
     *   be in to validate. For example, if `accept-field-states` is
     *   `['candidate', 'highlighted']`, then all the fields of the entity must
     *   be in either of these two states for the save or set call to
     *   validate and proceed.
     *
     * @return {string}
     *   A string to say something about the state of the entity model.
     */
    validate(attrs, options) {
      const acceptedFieldStates = options['accept-field-states'] || [];

      // Validate state change.
      const currentState = this.get('state');
      const nextState = attrs.state;
      if (currentState !== nextState) {
        // Ensure it's a valid state.
        if (_.indexOf(this.constructor.states, nextState) === -1) {
          return `"${nextState}" is an invalid state`;
        }

        // Ensure it's a state change that is allowed.
        // Check if the acceptStateChange function accepts it.
        if (!this._acceptStateChange(currentState, nextState, options)) {
          return 'state change not accepted';
        }
        // If that function accepts it, then ensure all fields are also in an
        // acceptable state.
        else if (!this._fieldsHaveAcceptableStates(acceptedFieldStates)) {
          return 'state change not accepted because fields are not in acceptable state';
        }
      }

      // Validate setting isCommitting = true.
      const currentIsCommitting = this.get('isCommitting');
      const nextIsCommitting = attrs.isCommitting;
      if (currentIsCommitting === false && nextIsCommitting === true) {
        if (!this._fieldsHaveAcceptableStates(acceptedFieldStates)) {
          return 'isCommitting change not accepted because fields are not in acceptable state';
        }
      }
      else if (currentIsCommitting === true && nextIsCommitting === true) {
        return 'isCommitting is a mutex, hence only changes are allowed';
      }
    },

    /**
     * Checks if a state change can be accepted.
     *
     * @param {string} from
     *   From state.
     * @param {string} to
     *   To state.
     * @param {object} context
     *   Context for the check.
     * @param {string} context.reason
     *   The reason for the state change.
     * @param {bool} context.confirming
     *   Whether context is confirming or not.
     *
     * @return {bool}
     *   Whether the state change is accepted or not.
     *
     * @see Drupal.quickedit.AppView#acceptEditorStateChange
     */
    _acceptStateChange(from, to, context) {
      let accept = true;

      // In general, enforce the states sequence. Disallow going back from a
      // "later" state to an "earlier" state, except in explicitly allowed
      // cases.
      if (!this.constructor.followsStateSequence(from, to)) {
        accept = false;

        // Allow: closing -> closed.
        // Necessary to stop editing an entity.
        if (from === 'closing' && to === 'closed') {
          accept = true;
        }
        // Allow: committing -> opened.
        // Necessary to be able to correct an invalid field, or to hit the
        // "Save" button again after a server/network error.
        else if (from === 'committing' && to === 'opened' && context.reason && (context.reason === 'invalid' || context.reason === 'networkerror')) {
          accept = true;
        }
        // Allow: deactivating -> opened.
        // Necessary to be able to confirm changes with the user.
        else if (from === 'deactivating' && to === 'opened' && context.confirming) {
          accept = true;
        }
        // Allow: opened -> deactivating.
        // Necessary to be able to stop editing.
        else if (from === 'opened' && to === 'deactivating' && context.confirmed) {
          accept = true;
        }
      }

      return accept;
    },

    /**
     * Checks if fields have acceptable states.
     *
     * @param {Array} acceptedFieldStates
     *   An array of acceptable field states to check for.
     *
     * @return {bool}
     *   Whether the fields have an acceptable state.
     *
     * @see Drupal.quickedit.EntityModel#validate
     */
    _fieldsHaveAcceptableStates(acceptedFieldStates) {
      let accept = true;

      // If no acceptable field states are provided, assume all field states are
      // acceptable. We want to let validation pass as a default and only
      // check validity on calls to set that explicitly request it.
      if (acceptedFieldStates.length > 0) {
        const fieldStates = this.get('fields').pluck('state') || [];
        // If not all fields are in one of the accepted field states, then we
        // still can't allow this state change.
        if (_.difference(fieldStates, acceptedFieldStates).length) {
          accept = false;
        }
      }

      return accept;
    },

    /**
     * Destroys the entity model.
     *
     * @param {object} options
     *   Options for the entity model.
     */
    destroy(options) {
      Drupal.quickedit.BaseModel.prototype.destroy.call(this, options);

      this.stopListening();

      // Destroy all fields of this entity.
      this.get('fields').reset();
    },

    /**
     * @inheritdoc
     */
    sync() {
      // We don't use REST updates to sync.

    },

  }, /** @lends Drupal.quickedit.EntityModel */{

    /**
     * Sequence of all possible states an entity can be in during quickediting.
     *
     * @type {Array.<string>}
     */
    states: [
      // Initial state, like field's 'inactive' OR the user has just finished
      // in-place editing this entity.
      // - Trigger: none (initial) or EntityModel (finished).
      // - Expected behavior: (when not initial state): tear down
      //   EntityToolbarView, in-place editors and related views.
      'closed',
      // User has activated in-place editing of this entity.
      // - Trigger: user.
      // - Expected behavior: the EntityToolbarView is gets set up, in-place
      //   editors (EditorViews) and related views for this entity's fields are
      //   set up. Upon completion of those, the state is changed to 'opening'.
      'launching',
      // Launching has finished.
      // - Trigger: application.
      // - Guarantees: in-place editors ready for use, all entity and field
      //   views have been set up, all fields are in the 'inactive' state.
      // - Expected behavior: all fields are changed to the 'candidate' state
      //   and once this is completed, the entity state will be changed to
      //   'opened'.
      'opening',
      // Opening has finished.
      // - Trigger: EntityModel.
      // - Guarantees: see 'opening', all fields are in the 'candidate' state.
      // - Expected behavior: the user is able to actually use in-place editing.
      'opened',
      // User has clicked the 'Save' button (and has thus changed at least one
      // field).
      // - Trigger: user.
      // - Guarantees: see 'opened', plus: either a changed field is in
      //   PrivateTempStore, or the user has just modified a field without
      //   activating (switching to) another field.
      // - Expected behavior: 1) if any of the fields are not yet in
      //   PrivateTempStore, save them to PrivateTempStore, 2) if then any of
      //   the fields has the 'invalid' state, then change the entity state back
      //   to 'opened', otherwise: save the entity by committing it from
      //   PrivateTempStore into permanent storage.
      'committing',
      // User has clicked the 'Close' button, or has clicked the 'Save' button
      // and that was successfully completed.
      // - Trigger: user or EntityModel.
      // - Guarantees: when having clicked 'Close' hardly any: fields may be in
      //   a variety of states; when having clicked 'Save': all fields are in
      //   the 'candidate' state.
      // - Expected behavior: transition all fields to the 'candidate' state,
      //   possibly requiring confirmation in the case of having clicked
      //   'Close'.
      'deactivating',
      // Deactivation has been completed.
      // - Trigger: EntityModel.
      // - Guarantees: all fields are in the 'candidate' state.
      // - Expected behavior: change all fields to the 'inactive' state.
      'closing',
    ],

    /**
     * Indicates whether the 'from' state comes before the 'to' state.
     *
     * @param {string} from
     *   One of {@link Drupal.quickedit.EntityModel.states}.
     * @param {string} to
     *   One of {@link Drupal.quickedit.EntityModel.states}.
     *
     * @return {bool}
     *   Whether the 'from' state comes before the 'to' state.
     */
    followsStateSequence(from, to) {
      return _.indexOf(this.states, from) < _.indexOf(this.states, to);
    },

  });

  /**
   * @constructor
   *
   * @augments Backbone.Collection
   */
  Drupal.quickedit.EntityCollection = Backbone.Collection.extend(/** @lends Drupal.quickedit.EntityCollection# */{

    /**
     * @type {Drupal.quickedit.EntityModel}
     */
    model: Drupal.quickedit.EntityModel,
  });
}(_, jQuery, Backbone, Drupal));