/********************************************************************************
 * Copyright (C) 2019 Ericsson and others.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the Eclipse
 * Public License v. 2.0 are satisfied: GNU General Public License, version 2
 * with the GNU Classpath Exception which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 ********************************************************************************/

import debounce = require('lodash.debounce');
import { Title, Widget } from '@phosphor/widgets';
import { inject, injectable, named, postConstruct } from 'inversify';
import { ContributionProvider, Disposable, DisposableCollection, Emitter, Event } from '@gedit/utils';
import { WidgetDecoration } from './widget-decoration';

export const TabBarDecorator = Symbol('TabBarDecorator');

export interface TabBarDecorator {

  /**
   * The unique identifier of the tab bar decorator.
   */
  readonly id: string;

  /**
   * Event that is fired when any of the available tab bar decorators has changes.
   */
  readonly onDidChangeDecorations: Event<void>;

  /**
   * Decorate title.
   * @param {Title<Widget>} title the title
   * @returns decoration data.
   */
  decorate(title: Title<Widget>): WidgetDecoration.Data[];
}

@injectable()
export class TabBarDecoratorService implements Disposable {

  protected readonly onDidChangeDecorationsEmitter = new Emitter<void>();

  readonly onDidChangeDecorations = this.onDidChangeDecorationsEmitter.event;

  protected readonly toDispose = new DisposableCollection();

  @inject(ContributionProvider) @named(TabBarDecorator)
  protected readonly contributions: ContributionProvider<TabBarDecorator>;
  protected fireDidChangeDecorations = debounce(() => this.onDidChangeDecorationsEmitter.fire(undefined), 150);

  dispose(): void {
    this.toDispose.dispose();
  }

  /**
   * Assign tabs the decorators provided by all the contributions.
   * @param {Title<Widget>} title the title
   * @returns an array of its decoration data.
   */
  getDecorations(title: Title<Widget>): WidgetDecoration.Data[] {
    const decorators = this.contributions.getContributions();
    let all: WidgetDecoration.Data[] = [];
    for (const decorator of decorators) {
      const decorations = decorator.decorate(title);
      all = all.concat(decorations);
    }
    return all;
  }

  @postConstruct()
  protected init(): void {
    const decorators = this.contributions.getContributions();
    this.toDispose.pushAll(decorators.map(decorator =>
      decorator.onDidChangeDecorations(this.fireDidChangeDecorations)
    ));
  }
}