// *****************************************************************************
// Copyright (C) 2024 STMicroelectronics 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 { Disposable, Emitter, Event } from '@theia/core';

const CHECK_INACTIVITY_LIMIT = 30;
const CHECK_INACTIVITY_INTERVAL = 1000;

const eventListenerOptions: AddEventListenerOptions = {
    passive: true,
    capture: true
};
export class WindowActivityTracker implements Disposable {

    private inactivityCounter = 0; // number of times inactivity was checked since last reset
    private readonly inactivityLimit = CHECK_INACTIVITY_LIMIT; // number of inactivity checks done before sending inactive signal
    private readonly checkInactivityInterval = CHECK_INACTIVITY_INTERVAL; // check interval in milliseconds
    private interval: NodeJS.Timeout | undefined;

    protected readonly onDidChangeActiveStateEmitter = new Emitter<boolean>();
    private _activeState: boolean = true;

    constructor(readonly win: Window) {
        this.initializeListeners(this.win);
    }

    get onDidChangeActiveState(): Event<boolean> {
        return this.onDidChangeActiveStateEmitter.event;
    }

    private set activeState(newState: boolean) {
        if (this._activeState !== newState) {
            this._activeState = newState;
            this.onDidChangeActiveStateEmitter.fire(this._activeState);
        }
    }

    private initializeListeners(win: Window): void {
        // currently assumes activity based on key/mouse/touch pressed, not on mouse move or scrolling.
        win.addEventListener('mousedown', this.resetInactivity, eventListenerOptions);
        win.addEventListener('keydown', this.resetInactivity, eventListenerOptions);
        win.addEventListener('touchstart', this.resetInactivity, eventListenerOptions);
    }

    dispose(): void {
        this.stopTracking();
        this.win.removeEventListener('mousedown', this.resetInactivity);
        this.win.removeEventListener('keydown', this.resetInactivity);
        this.win.removeEventListener('touchstart', this.resetInactivity);

    }

    // Reset inactivity time
    private resetInactivity = (): void => {
        this.inactivityCounter = 0;
        if (!this.interval) {
            // it was not active. Set as active and restart tracking inactivity
            this.activeState = true;
            this.startTracking();
        }
    };

    // Check inactivity status
    private checkInactivity = (): void => {
        this.inactivityCounter++;
        if (this.inactivityCounter >= this.inactivityLimit) {
            this.activeState = false;
            this.stopTracking();
        }
    };

    public startTracking(): void {
        this.stopTracking();
        this.interval = setInterval(this.checkInactivity, this.checkInactivityInterval);
    }

    public stopTracking(): void {
        if (this.interval) {
            clearInterval(this.interval);
            this.interval = undefined;
        }
    }
}