const Lang = imports.lang;
const GLib = imports.gi.GLib;

const Self = imports.misc.extensionUtils.getCurrentExtension();
const Prefs = Self.imports.settings;
const LoggerModule = Self.imports.logger;

let _afTimerInstance = null;

// Singleton implementation of _AFTimer
var AFTimer = function() {
    if (!_afTimerInstance) {
        _afTimerInstance = new _AFTimer();
    }
    return _afTimerInstance;
};

/**
 * Timer for the auto fetch feature.
 *
 * @type {Lang}
 */
var _AFTimer = new Lang.Class({
    Name: 'AFTimer',
	logger: null,

    _timeout: null,
    _timoutEndCallback: null,
    _minutes: 30,

    _init: function() {
		this.logger = new LoggerModule.Logger('RWG3', 'Timer');

        this._settings = new Prefs.Settings();
    },

    isActive: function () {
        return this._settings.get('auto-fetch', 'boolean');
    },

    remainingMinutes: function() {
        let minutesElapsed = this._minutesElapsed();
		let remainder = minutesElapsed % this._minutes;
		return Math.max(this._minutes - remainder, 0);
    },

    registerCallback: function(callback) {
        this._timoutEndCallback = callback;
    },

	/**
     * Sets the minutes of the timer.
     *
	 * @param minutes
	 */
	setMinutes: function(minutes) {
		this._minutes = minutes;
	},

    /**
     * Start the timer.
     *
     * @return void
     */
    start: function() {
		this.cleanup();

        let last = this._settings.get('timer-last-trigger', 'int64');
        if (last === 0) {
            this.reset();
        }

		let millisRemaining = this.remainingMinutes() * 60 * 1000;

		// set new wallpaper if the interval was surpassed and set the timestamp to when it should have been updated
		if (this._surpassedInterval()) {
			if (this._timoutEndCallback) {
				this._timoutEndCallback();
			}
			let millisOverdue = (this._minutes * 60 * 1000) - millisRemaining;
			this._settings.set('timer-last-trigger', 'int64', Date.now() - millisOverdue);
		}

		// actual timer function
		this._timeout = GLib.timeout_add(GLib.PRIORITY_DEFAULT, millisRemaining, () => {
            if (this._timoutEndCallback) {
                this._timoutEndCallback();
            }

            this.start(); // restart timer
        });
    },

    /**
     * Stop the timer.
     *
     * @return void
     */
    stop: function() {
        this._settings.set('timer-last-trigger', 'int64', 0);
        this.cleanup();
    },

    /**
     * Cleanup the timeout callback if it exists.
     *
     * @return void
     */
    cleanup: function() {
        if (this._timeout) { // only remove if a timeout is active
            GLib.source_remove(this._timeout);
            this._timeout = null;
        }
    },

    /**
     * Reset the timer.
     *
     * @return void
     */
    reset: function() {
        this._settings.set('timer-last-trigger', 'int64', new Date().getTime());
        this.cleanup();
    },

    _minutesElapsed: function() {
        let now = Date.now();
        let last = this._settings.get('timer-last-trigger', 'int64');

        if (last === 0) {
            return 0;
        }

        let elapsed = Math.max(now - last, 0);
        return Math.floor(elapsed / (60 * 1000));
    },

	_surpassedInterval: function() {
		let now = Date.now();
		let last = this._settings.get('timer-last-trigger', 'int64');
		let diff = now - last;
		let intervalLength = this._minutes * 60 * 1000;

		if (diff > intervalLength) {
			return true;
		}

    	return false;
	}


});