// Get the 2D context from the canvas in
//our HTML page
var canvas = document.getElementById("gameCanvas");
var context = canvas.getContext("2d");

// set up some event handlers to process keyboard input
window.addEventListener('keydown', function(evt) { onKeyDown(evt); }, false);
window.addEventListener('keyup', function(evt) { onKeyUp(evt); }, false);

var SCREEN_WIDTH = canvas.width;
var SCREEN_HEIGHT = canvas.height;

var ASTEROID_SPEED = 0.8;
var PLAYER_SPEED = 1;
var PLAYER_TURN_SPEED = 0.04;
var BULLET_SPEED = 1.5;

//this will create the player object and assigns it some properties
var player = {
	image: document.createElement("img"),
	x: SCREEN_WIDTH/2,
	y: SCREEN_HEIGHT/2,
	width: 93,
	height: 80,
	directionX: 0,
	directionY: 0,
	angularDirection: 0,
	rotation: 0
};

//players image here
player.image.src = "ship.png";


// key constants
// Go here for a list of key codes:
// https://developer.mozilla.org/en-US/docs/DOM/KeyboardEvent
var KEY_SPACE = 32;
var KEY_A = 65;
var KEY_W = 87;
var KEY_D = 68;
var KEY_S = 83;


//this creates the asteroid object and assigns it some properties
var asteroid = {
	image: document.createElement("img"),
	x: 100,
	y: 100,
	width: 69,
	height: 75,
	directionX: 0,
	directionY: 0,
	isDead: false
};

//set the image
asteroid.image.src = "rock_large.png";
asteroid.directionX = 10;
asteroid.directionY = 8;

//normalize the velocity (make it equal to 1)

var magnitude = Math.sqrt( (asteroid.directionX * asteroid.directionX) + (asteroid.directionY * asteroid.directionY) );

if (magnitude != 0)
	{
	asteroid.directionx /= magnitude;
	asteroid.directionY /= magnitude;
}

// this creates the bullet object and assigns it some properties
var bullet = {
image: document.createElement("img"),
x: player.x,
y: player.y,
width: 5,
height: 5,
velocityX: 0,
velocityY: 0,
isDead: true
};
// set the image for the asteroid to use
bullet.image.src = "bullet.png";

function playerShoot()
{
// we can only have 1 bullet at a time
if( bullet.isDead == false )
return;
// start off with a velocity that shoots the bullet straight up
var velX = 0;
var velY = 1;
// now rotate this vector acording to the ship's current rotation
var s = Math.sin(player.rotation);
var c = Math.cos(player.rotation);
// for an explanation of this formula,
// see http://en.wikipedia.org/wiki/Rotation_matrix
var xVel = (velX * c) - (velY * s);
var yVel = (velX * s) + (velY * c);
// dont bother storing a direction and calculating the
// velocity every frame, because it won't change.
// Just store the pre-calculated velocity
bullet.velocityX = xVel * BULLET_SPEED;
bullet.velocityY = yVel * BULLET_SPEED;
// don't forget to set the bullet's position
bullet.x = player.x;
bullet.y = player.y;
// make the bullet alive
bullet.isDead = false;


function onKeyDown(event)
{
if(event.keyCode == KEY_W)
{
player.directionY = 1;
}

if(event.keyCode == KEY_S)
{
player.directionY = -1;
}

if(event.keyCode == KEY_A)
{
player.angularDirection = -1;
}

if(event.keyCode == KEY_D)
{
player.angularDirection = 1;
}
}

function onKeyUp(event)
{
if(event.keyCode == KEY_W)
{
player.directionY = 0;
}
if(event.keyCode == KEY_S)
{
player.directionY = 0;
}
if(event.keyCode == KEY_A)
{
player.angularDirection = 0;
}
if(event.keyCode == KEY_D)
{
player.angularDirection = 0;
}
if(event.keyCode == KEY_SPACE)
{
playerShoot();
}

}


// tests if two rectangles are intersecting.
// Pass in the x,y coordinates, width and height of each rectangle.
// Returns 'true' if the rectangles are intersecting
function intersects(x1, y1, w1, h1, x2, y2, w2, h2)
{
if(y2 + h2 < y1 ||
x2 + w2 < x1 ||
x2 > x1 + w1 ||
y2 > y1 + h1)
{
return false;
}
return true;
}

function run()
{
context.fillStyle = "#8a2be2";
context.fillRect(0, 0, canvas.width, canvas.height);

// update and draw the bullet
// we want to do this first so that the plane is drawn on
// top of the bullet
if(bullet.isDead == false)
{
bullet.x += bullet.velocityX;
bullet.y += bullet.velocityY;
context.drawImage(bullet.image,
bullet.x - bullet.width/2,
bullet.y - bullet.height/2);

if(asteroid.isDead == false)
{
var hit = intersects(
bullet.x, bullet.y,
bullet.width, bullet.height,
asteroid.x, asteroid.y,
asteroid.width, asteroid.height);
if(hit == true)
{
bullet.isDead = true;
asteroid.isDead = true;
}
}
if(bullet.x < 0 || bullet.x > SCREEN_WIDTH ||
bullet.y < 0 || bullet.y > SCREEN_HEIGHT)
{
bullet.isDead = true;
}
}

//calculate sin and cos for the players current rotation
var s = Math.sin(player.rotation);
var c = Math.cos(player.rotation);

// figure out what the player's velocity will be based on the current rotation
// (so that if the ship is moving forward, then it will move forward according to its
// rotation. Without this, the ship would just move up the screen when we pressed 'up',
// regardless of which way it was rotated)
// for an explanation of this formula, see http://en.wikipedia.org/wiki/Rotation_matrix

var xDir = (player.directionX * c) - (player.directionY * s);
var yDir = (player.directionX * s) + (player.directionY * c);
var xVel = xDir * PLAYER_SPEED;
var yVel = yDir * PLAYER_SPEED;

player.x += xVel;
player.y += yVel;

player.rotation += player.angularDirection * PLAYER_TURN_SPEED;

context.save();
context.translate(player.X, player.Y);
context.rotate(player.rotation);
context.drawImage(player.image, -player.width/2, -player.height/2);
context.restore();

//update and draw asteroid
var velocityX = asteroid.directionX * ASTEROID_SPEED;
var velocityY = asteroid.directionY * ASTEROID_SPEED;
asteroid.x += velocityX;
asteroid.y += velocityY;
context.drawImage(asteroid.image,
asteroid.X - asteroid.width/2,
asteroid.y - asteroid.height/2);
}


















//-------------------- Don't modify anything below here
// This code will set up the framework so that the 'run' function is
// called 60 times per second. We have some options to fall back on
// in case the browser doesn't support our preferred method.
(function() {
 var onEachFrame;
 if (window.requestAnimationFrame) {
 onEachFrame = function(cb) {
 var _cb = function() { cb(); window.requestAnimationFrame(_cb); }
 _cb();
 };
 } else if (window.mozRequestAnimationFrame) {
 onEachFrame = function(cb) {
 var _cb = function() { cb();
window.mozRequestAnimationFrame(_cb); }
 _cb();
 };
 } else {
 onEachFrame = function(cb) {
 setInterval(cb, 1000 / 60);
 }
 }

 window.onEachFrame = onEachFrame;
})();
window.onEachFrame(run);