class ScoreManager {

	constructor() {
		this.score = 0;
		this.highScore = 0;

		this.onChangeScoreListeners = [];
		this.onChangeHighScoreListeners = [];
	}

	callListener(functionArray) {
		if(functionArray.length > 0) {
			for(let i = 0; i < functionArray.length; i++) {
				functionArray[i](this.score);
			}
		}
	}

	addOnChangeScoreListener(onChangeFunction) {
		this.onChangeScoreListeners.push(onChangeFunction);
	}

	removeOnChangeScoreListener(onChangeFunction) {
		let itemIndex = this.onChangeScoreListeners.indexOf(onChangeFunction);
		if(itemIndex > -1)
			this.onChangeScoreListeners.splice(itemIndex, 1);
	}

	addOnChangeHighScoreListener(onChangeHighScoreFunction) {
		this.onChangeHighScoreListeners.push(onChangeHighScoreFunction);
	}

	removeOnChangeHighScoreListener(onChangeHighScoreFunction) {
		let itemIndex = this.onChangeHighScoreListeners.indexOf(onChangeHighScoreFunction);
		if(itemIndex > -1)
			this.onChangeHighScoreListeners.splice(itemIndex, 1);
	}

	removeAllListeners() {
		this.onChangeScoreListeners = [];
		this.onChangeHighScoreListeners = [];
	}


	getScore() {
		return this.score;
	}

	getHighScore() {
		return this.highScore;
	}


	plusScore(amount) {
		this.setScore(this.score + amount);
	}

	minusScore(amount) {
		this.plusScore(-1 * amount);
	}

	setScore(value) {
		let beforeScore = this.score;
		this.score = value;

		// update score
		if(beforeScore !== this.score)
			this.callListener(this.onChangeScoreListeners);

		// update high score
		if(this.score > this.highScore)
			this.callListener(this.onChangeHighScoreListeners);
	}

}