/**
 * @license
 * Copyright 2018 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @fileoverview Abstract class for events fired as a result of actions in
 * Blockly's editor.
 */
'use strict';

/**
 * Abstract class for events fired as a result of actions in
 * Blockly's editor.
 * @class
 */
goog.module('Blockly.Events.Abstract');

const eventUtils = goog.require('Blockly.Events.utils');
/* eslint-disable-next-line no-unused-vars */
const {Workspace} = goog.requireType('Blockly.Workspace');


/**
 * Abstract class for an event.
 * @abstract
 * @alias Blockly.Events.Abstract
 */
class Abstract {
  /**
   * @alias Blockly.Events.Abstract
   */
  constructor() {
    /**
     * Whether or not the event is blank (to be populated by fromJson).
     * @type {?boolean}
     */
    this.isBlank = null;

    /**
     * The workspace identifier for this event.
     * @type {string|undefined}
     */
    this.workspaceId = undefined;

    /**
     * The event group id for the group this event belongs to. Groups define
     * events that should be treated as an single action from the user's
     * perspective, and should be undone together.
     * @type {string}
     */
    this.group = eventUtils.getGroup();

    /**
     * Sets whether the event should be added to the undo stack.
     * @type {boolean}
     */
    this.recordUndo = eventUtils.getRecordUndo();

    /**
     * Whether or not the event is a UI event.
     * @type {boolean}
     */
    this.isUiEvent = false;

    /**
     * Type of this event.
     * @type {string|undefined}
     */
    this.type = undefined;
  }

  /**
   * Encode the event as JSON.
   * @return {!Object} JSON representation.
   */
  toJson() {
    const json = {'type': this.type};
    if (this.group) {
      json['group'] = this.group;
    }
    return json;
  }

  /**
   * Decode the JSON event.
   * @param {!Object} json JSON representation.
   */
  fromJson(json) {
    this.isBlank = false;
    this.group = json['group'];
  }

  /**
   * Does this event record any change of state?
   * @return {boolean} True if null, false if something changed.
   */
  isNull() {
    return false;
  }

  /**
   * Run an event.
   * @param {boolean} _forward True if run forward, false if run backward
   *     (undo).
   */
  run(_forward) {
    // Defined by subclasses.
  }

  /**
   * Get workspace the event belongs to.
   * @return {!Workspace} The workspace the event belongs to.
   * @throws {Error} if workspace is null.
   * @protected
   */
  getEventWorkspace_() {
    let workspace;
    if (this.workspaceId) {
      const {Workspace} = goog.module.get('Blockly.Workspace');
      workspace = Workspace.getById(this.workspaceId);
    }
    if (!workspace) {
      throw Error(
          'Workspace is null. Event must have been generated from real' +
          ' Blockly events.');
    }
    return workspace;
  }
}

exports.Abstract = Abstract;