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

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

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

      /**
       * The DOM element that represents this field. It may seem bizarre to have
       * a DOM element in a Backbone Model, but we need to be able to map fields
       * in the DOM to FieldModels in memory.
       */
      el: null,

      /**
       * A field ID, of the form
       * `<entity type>/<id>/<field name>/<language>/<view mode>`
       *
       * @example
       * "node/1/field_tags/und/full"
       */
      fieldID: null,

      /**
       * The unique ID of this field within its entity instance on the page, of
       * the form `<entity type>/<id>/<field name>/<language>/<view
       * mode>[entity instance ID]`.
       *
       * @example
       * "node/1/field_tags/und/full[0]"
       */
      id: null,

      /**
       * A {@link Drupal.quickedit.EntityModel}. Its "fields" attribute, which
       * is a FieldCollection, is automatically updated to include this
       * FieldModel.
       */
      entity: null,

      /**
       * This field's metadata as returned by the
       * QuickEditController::metadata().
       */
      metadata: null,

      /**
       * Callback function for validating changes between states. Receives the
       * previous state, new state, context, and a callback.
       */
      acceptStateChange: null,

      /**
       * A logical field ID, of the form
       * `<entity type>/<id>/<field name>/<language>`, i.e. the fieldID without
       * the view mode, to be able to identify other instances of the same
       * field on the page but rendered in a different view mode.
       *
       * @example
       * "node/1/field_tags/und".
       */
      logicalFieldID: null,

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

      /**
       * In-place editing state of this field. Defaults to the initial state.
       * Possible values: {@link Drupal.quickedit.FieldModel.states}.
       */
      state: 'inactive',

      /**
       * The field is currently in the 'changed' state or one of the following
       * states in which the field is still changed.
       */
      isChanged: false,

      /**
       * Is tracked by the EntityModel, is mirrored here solely for decorative
       * purposes: so that FieldDecorationView.renderChanged() can react to it.
       */
      inTempStore: false,

      /**
       * The full HTML representation of this field (with the element that has
       * the data-quickedit-field-id as the outer element). Used to propagate
       * changes from this field to other instances of the same field storage.
       */
      html: null,

      /**
       * An object containing the full HTML representations (values) of other
       * view modes (keys) of this field, for other instances of this field
       * displayed in a different view mode.
       */
      htmlForOtherViewModes: null,
    },

    /**
     * State of an in-place editable field in the DOM.
     *
     * @constructs
     *
     * @augments Drupal.quickedit.BaseModel
     *
     * @param {object} options
     *   Options for the field model.
     */
    initialize(options) {
      // Store the original full HTML representation of this field.
      this.set('html', options.el.outerHTML);

      // Enlist field automatically in the associated entity's field collection.
      this.get('entity').get('fields').add(this);

      // Automatically generate the logical field ID.
      this.set('logicalFieldID', this.get('fieldID').split('/').slice(0, 4).join('/'));

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

    /**
     * Destroys the field model.
     *
     * @param {object} options
     *   Options for the field model.
     */
    destroy(options) {
      if (this.get('state') !== 'inactive') {
        throw new Error('FieldModel cannot be destroyed if it is not inactive state.');
      }
      Drupal.quickedit.BaseModel.prototype.destroy.call(this, options);
    },

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

    },

    /**
     * Validate function for the field 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 field model.
     */
    validate(attrs, options) {
      const current = this.get('state');
      const next = attrs.state;
      if (current !== next) {
        // Ensure it's a valid state.
        if (_.indexOf(this.constructor.states, next) === -1) {
          return `"${next}" is an invalid state`;
        }
        // Check if the acceptStateChange callback accepts it.
        if (!this.get('acceptStateChange')(current, next, options, this)) {
          return 'state change not accepted';
        }
      }
    },

    /**
     * Extracts the entity ID from this field's ID.
     *
     * @return {string}
     *   An entity ID: a string of the format `<entity type>/<id>`.
     */
    getEntityID() {
      return this.get('fieldID').split('/').slice(0, 2).join('/');
    },

    /**
     * Extracts the view mode ID from this field's ID.
     *
     * @return {string}
     *   A view mode ID.
     */
    getViewMode() {
      return this.get('fieldID').split('/').pop();
    },

    /**
     * Find other instances of this field with different view modes.
     *
     * @return {Array}
     *   An array containing view mode IDs.
     */
    findOtherViewModes() {
      const currentField = this;
      const otherViewModes = [];
      Drupal.quickedit.collections.fields
        // Find all instances of fields that display the same logical field
        // (same entity, same field, just a different instance and maybe a
        // different view mode).
        .where({ logicalFieldID: currentField.get('logicalFieldID') })
        .forEach((field) => {
          // Ignore the current field.
          if (field === currentField) {

          }
          // Also ignore other fields with the same view mode.
          else if (field.get('fieldID') === currentField.get('fieldID')) {

          }
          else {
            otherViewModes.push(field.getViewMode());
          }
        });
      return otherViewModes;
    },

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

    /**
     * Sequence of all possible states a field can be in during quickediting.
     *
     * @type {Array.<string>}
     */
    states: [
      // The field associated with this FieldModel is linked to an EntityModel;
      // the user can choose to start in-place editing that entity (and
      // consequently this field). No in-place editor (EditorView) is associated
      // with this field, because this field is not being in-place edited.
      // This is both the initial (not yet in-place editing) and the end state
      // (finished in-place editing).
      'inactive',
      // The user is in-place editing this entity, and this field is a
      // candidate
      // for in-place editing. In-place editor should not
      // - Trigger: user.
      // - Guarantees: entity is ready, in-place editor (EditorView) is
      //   associated with the field.
      // - Expected behavior: visual indicators
      //   around the field indicate it is available for in-place editing, no
      //   in-place editor presented yet.
      'candidate',
      // User is highlighting this field.
      // - Trigger: user.
      // - Guarantees: see 'candidate'.
      // - Expected behavior: visual indicators to convey highlighting, in-place
      //   editing toolbar shows field's label.
      'highlighted',
      // User has activated the in-place editing of this field; in-place editor
      // is activating.
      // - Trigger: user.
      // - Guarantees: see 'candidate'.
      // - Expected behavior: loading indicator, in-place editor is loading
      //   remote data (e.g. retrieve form from back-end). Upon retrieval of
      //   remote data, the in-place editor transitions the field's state to
      //   'active'.
      'activating',
      // In-place editor has finished loading remote data; ready for use.
      // - Trigger: in-place editor.
      // - Guarantees: see 'candidate'.
      // - Expected behavior: in-place editor for the field is ready for use.
      'active',
      // User has modified values in the in-place editor.
      // - Trigger: user.
      // - Guarantees: see 'candidate', plus in-place editor is ready for use.
      // - Expected behavior: visual indicator of change.
      'changed',
      // User is saving changed field data in in-place editor to
      // PrivateTempStore. The save mechanism of the in-place editor is called.
      // - Trigger: user.
      // - Guarantees: see 'candidate' and 'active'.
      // - Expected behavior: saving indicator, in-place editor is saving field
      //   data into PrivateTempStore. Upon successful saving (without
      //   validation errors), the in-place editor transitions the field's state
      //   to 'saved', but to 'invalid' upon failed saving (with validation
      //   errors).
      'saving',
      // In-place editor has successfully saved the changed field.
      // - Trigger: in-place editor.
      // - Guarantees: see 'candidate' and 'active'.
      // - Expected behavior: transition back to 'candidate' state because the
      //   deed is done. Then: 1) transition to 'inactive' to allow the field
      //   to be rerendered, 2) destroy the FieldModel (which also destroys
      //   attached views like the EditorView), 3) replace the existing field
      //   HTML with the existing HTML and 4) attach behaviors again so that the
      //   field becomes available again for in-place editing.
      'saved',
      // In-place editor has failed to saved the changed field: there were
      // validation errors.
      // - Trigger: in-place editor.
      // - Guarantees: see 'candidate' and 'active'.
      // - Expected behavior: remain in 'invalid' state, let the user make more
      //   changes so that he can save it again, without validation errors.
      'invalid',
    ],

    /**
     * Indicates whether the 'from' state comes before the 'to' state.
     *
     * @param {string} from
     *   One of {@link Drupal.quickedit.FieldModel.states}.
     * @param {string} to
     *   One of {@link Drupal.quickedit.FieldModel.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.FieldCollection = Backbone.Collection.extend(/** @lends Drupal.quickedit.FieldCollection */{

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