/**** 
* Classes
****/
// Missile class
// Alien class
var Asteroid = Container.expand(function () {
	var self = Container.call(this);
	var asteroidGraphics = self.attachAsset('asteroid', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.speed = 2;
	self.move = function () {
		var dy = earth.y - self.y;
		var dx = earth.x - self.x;
		var angle = Math.atan2(dy, dx);
		self.x += self.speed * Math.cos(angle);
		self.y += self.speed * Math.sin(angle);
	};
});
// Shield class
var Shield = Container.expand(function () {
	var self = Container.call(this);
	self.attachAsset('shield', {
		anchorX: 0.5,
		anchorY: 0.5
	});
	self.orbitRadius = 200;
	self.orbitSpeed = 0.04;
	self.orbitAngle = 0;
	self.update = function () {
		self.orbitAngle += self.orbitSpeed;
		self.x = earth.x + self.orbitRadius * Math.cos(self.orbitAngle);
		self.y = earth.y + self.orbitRadius * Math.sin(self.orbitAngle);
		var angleToEarth = Math.atan2(earth.y - self.y, earth.x - self.x);
		self.rotation = angleToEarth + Math.PI / 2;
	};
});

/**** 
* Initialize Game
****/
var game = new LK.Game({
	backgroundColor: 0x000000 // Init game with black background
});

/**** 
* Game Code
****/
// Initialize assets used in the game.
// Game variables
var asteroids = [];
var earth;
var scoreTxt;
var spawnAlienInterval = 120; // Frames until a new alien spawns
var nextAlienSpawn = spawnAlienInterval;
// Initialize Earth
function initEarth() {
	earth = game.addChild(LK.getAsset('earth', {
		anchorX: 0.5,
		anchorY: 0.5,
		x: game.width / 2,
		y: game.height / 2
	}));
	window.shield = game.addChild(new Shield());
	window.shield.x = earth.x;
	window.shield.y = earth.y - window.shield.orbitRadius;
}
// Initialize score display
function initScore() {
	scoreTxt = new Text2('0', {
		size: 150,
		fill: "#ffffff"
	});
	scoreTxt.anchor.set(0.5, 0);
	LK.gui.top.addChild(scoreTxt);
}
// Spawn an alien
function spawnAsteroid() {
	var asteroid = new Asteroid();
	var side = Math.floor(Math.random() * 4);
	switch (side) {
		case 0:
			// top
			asteroid.x = Math.random() * game.width;
			asteroid.y = -asteroid.height;
			break;
		case 1:
			// right
			asteroid.x = game.width + asteroid.width;
			asteroid.y = Math.random() * game.height;
			break;
		case 2:
			// bottom
			asteroid.x = Math.random() * game.width;
			asteroid.y = game.height + asteroid.height;
			break;
		case 3:
			// left
			asteroid.x = -asteroid.width;
			asteroid.y = Math.random() * game.height;
			break;
	}
	asteroids.push(asteroid);
	game.addChild(asteroid);
}
// Check for collisions
function checkCollisions() {
	for (var i = 0; i < asteroids.length; i++) {
		if (window.shield.intersects(asteroids[i])) {
			asteroids[i].destroy();
			asteroids.splice(i, 1);
		}
	}
}
// Game over check
function checkGameOver() {
	for (var i = 0; i < asteroids.length; i++) {
		if (asteroids[i].intersects(earth)) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
			break;
		}
	}
}
// Touch event to move shield
game.on('down', function (obj) {
	window.shield.orbitSpeed *= -1;
});
// Game tick event
LK.on('tick', function () {
	// Move asteroids
	for (var j = asteroids.length - 1; j >= 0; j--) {
		asteroids[j].move();
		if (asteroids[j].y > game.height + asteroids[j].height) {
			asteroids[j].destroy();
			asteroids.splice(j, 1);
		}
	}
	// Spawn asteroids
	nextAlienSpawn--;
	if (nextAlienSpawn <= 0) {
		spawnAsteroid();
		nextAlienSpawn = spawnAlienInterval;
	}
	// Update shield position
	window.shield.update();
	// Check for collisions and game over
	checkCollisions();
	checkGameOver();
});
// Initialize game elements
initEarth();
initScore();