/********************************************************************************
* Copyright (c) 2021 STMicroelectronics and others.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 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
*******************************************************************************/

/* eslint-disable @typescript-eslint/no-explicit-any */

import { inject, injectable } from 'inversify';
import { Measurement, MeasurementOptions } from './measurement';
import { Stopwatch } from './stopwatch';

export const BackendStopwatch = Symbol('BackendStopwatch');

/** API path of the stopwatch service that exposes the back-end stopwatch to clients. */
export const stopwatchPath = '/services/stopwatch';

/** Token representing a remote measurement in the {@link BackendStopwatch} protocol. */
export type RemoteMeasurement = number;

export const BackendStopwatchOptions = Symbol('BackendStopwatchOptions');

/**
 * A service that exposes the back-end's {@link Stopwatch} to clients
 * via the remote API. If you do not need this service then bind or re-bind
 * the {@link NullBackendStopwatch} implementation to this service interface.
 */
export interface BackendStopwatch {

    /**
     * Create a {@link Measurement} that will compute the time that elapsed on the back-end when logged.
     *
     * @param name the {@link Measurement.name measurement name}
     * @param options optional configuration of the new measurement
     * @returns a token identifying an unique self-timing measurement relative to the back-end's timeline
     */
    start(name: string, options?: MeasurementOptions): Promise<RemoteMeasurement>;

    /**
     * Stop a measurement previously {@link start started} and log in the back-end a measurement of
     * its duration relative to the back-end's timeline.
     *
     * @param measurement token identifying a measurement previously {@link start started}
     * @param message a message to log
     * @param messageArgs optional arguments to the `message`
     */
    stop(measurement: RemoteMeasurement, message: string, messageArgs: any[]): Promise<void>;

}

/**
 * Default implementation of the (remote) back-end stopwatch service.
 */
@injectable()
export class DefaultBackendStopwatch {

    readonly measurements = new Map<number, Measurement>();

    protected idSequence: number = 0;

    @inject(Stopwatch)
    protected readonly stopwatch: Stopwatch;

    start(name: string, options?: MeasurementOptions): RemoteMeasurement {
        const result = ++this.idSequence;
        this.measurements.set(result, this.stopwatch.start(name, options));
        return result;
    }

    stop(measurementToken: RemoteMeasurement, message: string, messageArgs: any[]): void {
        const measurement = this.measurements.get(measurementToken);
        if (measurement) {
            this.measurements.delete(measurementToken);
            measurement.log(message, ...messageArgs);
        }
    }

}

/**
 * No-op implementation of the (remote) back-end stopwatch service.
 */
@injectable()
export class NullBackendStopwatch implements BackendStopwatch {

    start(): Promise<RemoteMeasurement> {
        return Promise.resolve(0);
    }

    stop(): Promise<void> {
        return Promise.resolve();
    }

}