// *****************************************************************************
// 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 } from 'inversify';
import { Event, Emitter, ContributionProvider } from '../../common';
import { WidgetDecoration } from '../widget-decoration';
import { FrontendApplicationContribution } from '../frontend-application';

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 FrontendApplicationContribution {

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

    readonly onDidChangeDecorations = this.onDidChangeDecorationsEmitter.event;

    @inject(ContributionProvider) @named(TabBarDecorator)
    protected readonly contributions: ContributionProvider<TabBarDecorator>;

    initialize(): void {
        this.contributions.getContributions().map(decorator => decorator.onDidChangeDecorations(this.fireDidChangeDecorations));
    }

    fireDidChangeDecorations = debounce(() => this.onDidChangeDecorationsEmitter.fire(undefined), 150);

    /**
     * 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;
    }
}