// *****************************************************************************
// Copyright (C) 2018 Red Hat, Inc. 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-only WITH Classpath-exception-2.0
// *****************************************************************************

import { injectable, inject, postConstruct } from '@theia/core/shared/inversify';
import { Disposable } from '@theia/core/lib/common/disposable';
import { ProcessTaskRunner } from './process/process-task-runner';
import { TaskRunner } from './task-runner-protocol';
export { TaskRunner };

export const TaskRunnerContribution = Symbol('TaskRunnerContribution');

/** The {@link TaskRunnerContribution} can be used to contribute custom {@link TaskRunner}s. */
export interface TaskRunnerContribution {
    /**
     * Register custom runners using the given {@link TaskRunnerRegistry}.
     * @param runners the common task runner registry.
     */
    registerRunner(runners: TaskRunnerRegistry): void;
}

/**
 * The {@link TaskRunnerRegistry} is the common component for the registration and provisioning of
 * {@link TaskRunner}s. Theia will collect all {@link TaskRunner}s and invoke {@link TaskRunnerContribution#registerRunner}
 * for each contribution. The `TaskServer` will use the runners provided by this registry to execute `TaskConfiguration`s that
 * have been triggered by the user.
 */
@injectable()
export class TaskRunnerRegistry {

    protected runners: Map<string, TaskRunner>;
    /** A Task Runner that will be used for executing a Task without an associated Runner. */
    protected defaultRunner: TaskRunner;

    @inject(ProcessTaskRunner)
    protected readonly processTaskRunner: ProcessTaskRunner;

    @postConstruct()
    protected init(): void {
        this.runners = new Map();
        this.defaultRunner = this.processTaskRunner;
    }
    /**
     * Registers the given {@link TaskRunner} to execute Tasks of the specified type.
     * If there is already a {@link TaskRunner} registered for the specified type the registration will
     * be overwritten with the new value.
     * @param type the task type for which the given runner should be registered.
     * @param runner the task runner that should be registered.
     *
     * @returns a `Disposable` that can be invoked to unregister the given runner.
     */
    registerRunner(type: string, runner: TaskRunner): Disposable {
        this.runners.set(type, runner);
        return {
            dispose: () => this.runners.delete(type)
        };
    }

    /**
     * Looks for a registered {@link TaskRunner} for each of the task types in sequence and returns the first that is found
     * If no task runner is registered for any of the types, the default runner is returned.
     * @param types the task types.
     *
     * @returns the registered {@link TaskRunner} or a default runner if none is registered for the specified types.
     */
    getRunner(...types: string[]): TaskRunner {
        for (const type of types) {
            const runner = this.runners.get(type);
            if (runner) {
                return runner;
            }
        }
        return this.defaultRunner;
    }

    /**
     * Derives all task types for which a {@link TaskRunner} is registered.
     *
     * @returns all derived task types.
     */
    getRunnerTypes(): string[] {
        return [...this.runners.keys()];
    }
}