class AlienTimer {

	constructor(aliens) {
		this.aliens = aliens;
		this.activatedAlienIndex = 0;

		let posX = this.aliens[0].x;
		let posY = this.aliens[0].y - AlienTimer.MOVE_UP_AMOUNT_PX;
		this.timerText = game.add.text(posX, posY, "30", AlienTimer.DEFAULT_TEXT_FONT);
		this.timerText.anchor.set(0.5);

		var grd = this.timerText.context.createLinearGradient(0, 0, 0, this.timerText.height);
		grd.addColorStop(0, '#FFD68E');
		grd.addColorStop(1, '#B34C00');
		this.timerText.fill = grd;
		// this.setShadow(3, 3, 'rgba(0, 0, 0, 0.5)', 2);
		this.timerText.stroke = '#000';
		this.timerText.strokeThickness = 5;

		this.timerEvent = null;
		this.timeInterval = AlienTimer.DEFAULT_TIME_GAP_SEC;
		this.timeLeft = this.timeInterval;
	}

	start() {
		this.enableTimerOn(this.getActivatedAlien());
		// this.getActivatedAlien().setActive(true);
		this.timerText.text = this.timeLeft.toString();
		if(this.timerEvent === null)
			this.timerEvent = game.time.events.loop(Phaser.Timer.SECOND, this.updateTimer, this);
	}

	pause() {
	}

	stop() {
		if(this.timerEvent)
			this.removeTimer();
		this.timerText.text = "";

		for(let i = 0; i < this.aliens.length; i++)
			this.aliens[i].stop();
	}

	next() {
		this.timeLeft = this.timeInterval;
		this.timerText.text = this.timeLeft.toString();

		this.activatedAlienIndex++;
		if(this.activatedAlienIndex >= this.aliens.length) {
			this.timerText.text = "";
			this.removeTimer();
			return null;
		}

		this.enableTimerOn(this.getActivatedAlien());
	}

	getActivatedAlien() {
		return this.aliens[this.activatedAlienIndex];
	}

	enableTimerOn(alien) {
		alien.setActive(true);
		this.timerText.x = alien.x;
	}

	disableTimerOn(alien) {
		alien.setActive(false);
		this.timerText.text = "";
	}

	updateTimer() {
		this.timeLeft--;
		if(this.timeLeft == 0) {
			this.timeLeft = this.timeInterval;

			this.getActivatedAlien().goOnstage();
		} else {
			this.timerText.text = this.timeLeft.toString();
		}
	}

	removeTimer() {
		game.time.events.remove(this.timerEvent);
		this.timerEvent = null;
	}

}

AlienTimer.DEFAULT_TEXT_FONT		= {
	font: "bold 30px Arial",
	boundsAlignH: "center",		// left, center. right
	boundsAlignV: "middle", 	// top, middle, bottom
	fill: "#fff"
};

AlienTimer.DEFAULT_TIME_GAP_SEC		= 10;
AlienTimer.MOVE_UP_AMOUNT_PX		= 60;