/********************************************************************************
 * 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 { injectable } from 'inversify';
import { CancellationToken } from '@gedit/utils';
import { ProgressClient } from '@gedit/connection';
import { ProgressMessage, ProgressUpdate } from '@gedit/connection';
import { PromiseDeferred } from '@gedit/utils';
import { Emitter, Event } from '@gedit/utils';

export interface LocationProgress {
  show: boolean;
}

@injectable()
export class ProgressLocationService implements ProgressClient {

  protected emitters = new Map<string, Emitter<LocationProgress>[]>();
  protected lastEvents = new Map<string, LocationProgress>();
  protected readonly progressByLocation = new Map<string, Set<string>>();

  getProgress(locationId: string): LocationProgress | undefined {
    return this.lastEvents.get(locationId);
  }

  onProgress(locationId: string): Event<LocationProgress> {
    const emitter = this.addEmitter(locationId);
    return emitter.event;
  }

  async showProgress(progressId: string, message: ProgressMessage, cancellationToken: CancellationToken): Promise<string | undefined> {
    const locationId = this.getLocationId(message);
    const result = new PromiseDeferred<string | undefined>();
    cancellationToken.onCancellationRequested(() => {
      this.processEvent(progressId, locationId, 'done');
      result.resolve(ProgressMessage.Cancel);
    });
    this.processEvent(progressId, locationId, 'start');
    return result.promise;
  }

  async reportProgress(progressId: string, update: ProgressUpdate, message: ProgressMessage, cancellationToken: CancellationToken): Promise<void> {
    /* NOOP */
  }

  protected addEmitter(locationId: string): Emitter<LocationProgress> {
    const emitter = new Emitter<LocationProgress>();
    const list = this.emitters.get(locationId) || [];
    list.push(emitter);
    this.emitters.set(locationId, list);
    return emitter;
  }

  protected processEvent(progressId: string, locationId: string, event: 'start' | 'done'): void {
    const progressSet = this.progressByLocation.get(locationId) || new Set<string>();
    if (event === 'start') {
      progressSet.add(progressId);
    } else {
      progressSet.delete(progressId);
    }
    this.progressByLocation.set(locationId, progressSet);
    const show = !!progressSet.size;
    this.fireEvent(locationId, show);
  }

  protected fireEvent(locationId: string, show: boolean): void {
    const lastEvent = this.lastEvents.get(locationId);
    const shouldFire = !lastEvent || lastEvent.show !== show;
    if (shouldFire) {
      this.lastEvents.set(locationId, {show});
      this.getOrCreateEmitters(locationId).forEach(e => e.fire({show}));
    }
  }

  protected getOrCreateEmitters(locationId: string): Emitter<LocationProgress>[] {
    let emitters = this.emitters.get(locationId);
    if (!emitters) {
      emitters = [this.addEmitter(locationId)];
    }
    return emitters;
  }

  protected getLocationId(message: ProgressMessage): string {
    return message.options && message.options.location || 'unknownLocation';
  }

}