/********************************************************************************
 * Copyright (C) 2019 TypeFox 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 { FrontendApplicationContribution } from '@gedit/application-common/lib/browser';
import { ApplicationShell } from './application-shell';
import { inject, injectable } from 'inversify';
import { Disposable, DisposableCollection } from '@gedit/utils';
import { Emitter, Event } from '@gedit/utils';
import { FocusTracker, PanelLayout, SplitPanel } from '@phosphor/widgets';
import { addEventListener, Widget } from '../widgets';

/**
 * Contribution that tracks `mouseup` and `mousedown` events.
 *
 * This is required to be able to track the `TabBar`, `DockPanel`, and `SidePanel` resizing and drag and drop events correctly
 * all over the application. By default, when the mouse is over an `iframe` we lose the mouse tracking ability, so whenever
 * we click (`mousedown`), we overlay a transparent `div` over the `iframe` in the Mini Browser, then we set the `display` of
 * the transparent `div` to `none` on `mouseup` events.
 */
@injectable()
export class ApplicationShellMouseTracker implements FrontendApplicationContribution {

  @inject(ApplicationShell)
  protected readonly applicationShell: ApplicationShell;

  protected readonly toDispose = new DisposableCollection();
  protected readonly toDisposeOnActiveChange = new DisposableCollection();

  protected readonly mouseupEmitter = new Emitter<MouseEvent>();
  protected readonly mousedownEmitter = new Emitter<MouseEvent>();

  get onMouseup(): Event<MouseEvent> {
    return this.mouseupEmitter.event;
  }

  get onMousedown(): Event<MouseEvent> {
    return this.mousedownEmitter.event;
  }

  onStart(): void {
    // Here we need to attach a `mousedown` listener to the `TabBar`s, `DockPanel`s and the `SidePanel`s. Otherwise, Phosphor handles the event and stops the propagation.
    // Track the `mousedown` on the `TabBar` for the currently active widget.
    this.applicationShell.activeChanged.connect((shell: ApplicationShell, args: FocusTracker.IChangedArgs<Widget>) => {
      this.toDisposeOnActiveChange.dispose();
      if (args.newValue) {
        const tabBar = shell.getTabBarFor(args.newValue);
        if (tabBar) {
          this.toDisposeOnActiveChange.push(addEventListener(tabBar.node, 'mousedown', this.mousedownListener, true));
        }
      }
    });

    // Track the `mousedown` events for the `SplitPanel`s, if any.
    const {layout} = this.applicationShell;
    if (layout instanceof PanelLayout) {
      this.toDispose.pushAll(
        layout.widgets.filter(ApplicationShellMouseTracker.isSplitPanel).map(splitPanel => addEventListener(splitPanel.node, 'mousedown', this.mousedownListener, true))
      );
    }
    // Track the `mousedown` on each `DockPanel`.
    const {mainPanel, bottomPanel, leftPanelHandler, rightPanelHandler} = this.applicationShell;
    this.toDispose.pushAll([mainPanel, bottomPanel, leftPanelHandler.dockPanel, rightPanelHandler.dockPanel]
      .map(panel => addEventListener(panel.node, 'mousedown', this.mousedownListener, true)));

    // The `mouseup` event has to be tracked on the `document`. Phosphor attaches to there.
    document.addEventListener('mouseup', this.mouseupListener, true);

    // Make sure it is disposed in the end.
    this.toDispose.pushAll([
      this.mousedownEmitter,
      this.mouseupEmitter,
      Disposable.create(() => document.removeEventListener('mouseup', this.mouseupListener, true))
    ]);
  }

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

  protected readonly mouseupListener: (e: MouseEvent) => void = e => this.mouseupEmitter.fire(e);

  protected readonly mousedownListener: (e: MouseEvent) => void = e => this.mousedownEmitter.fire(e);

}

export namespace ApplicationShellMouseTracker {

  export function isSplitPanel(arg: Widget): arg is SplitPanel {
    return arg instanceof SplitPanel;
  }

}