window.addEventListener("keydown", moveSnake, false);
var game_over = false;
var snake = new Array(4);
var snakeLen = 4;
var dir = "right";
var food = "";
var level = new Array();
var total_height = 640;
var total_width = 640;
var lvl_width = 20;
var lvl_height = 20;
var speed = 16;
 
snakeHeadImage = new Image();
snakeHeadImage.src = "resources/head.png";
snakeBodyImage = new Image();
snakeBodyImage.src = "resources/body.png";
snakeTailImage = new Image();
snakeTailImage.src = "resources/tail.png";
 
//food
foodImage = new Image();
foodImage.src = "resources/food.png";
 
create_snake();
create_food();
 
for(i = 0; i < lvl_width; i++)
{
    level[i] = new Array(lvl_height);
    for(var ii = 0; ii < lvl_height; ii++)
    {
        level[i][ii] = -1;
    }
}
 
window.requestAnimFrame = (function(callback) 
{
    return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame ||
    function(callback) 
    {
        window.setTimeout(callback, 1000);
    };
})();
 
 
var the_date = new Date();
var test1 = the_date.getTime();
var stamp = the_date.getTime() + 250;
 
function animate() 
{
    the_date = new Date();
    test1 = the_date.getTime();
    if(stamp <= test1)
    {
        move_snake();
        the_date = new Date();
        stamp = the_date.getTime() + 250;
    }
    if(game_over == false)
    {
        // clear
        context.clearRect(0, 0, canvas.width, canvas.height);
        displayText("Score: " + (snakeLen - 4));
        display();
    }
    else
    {
        displayText("You so Sux.. Game Over homie");
    }
    //context.drawImage(aniblock, aniblock_x, aniblock_y); 
 
    // request new frame
    requestAnimFrame(function()
    {
      animate();
    });
} 
 
function displayText(what)
{
    context.font = "30px Arial";
    context.fillText(what, 50, 50);
}
 
function checkSnakeCollide()
{
    if( snake[0].xx == food.xx && snake[0].yy == food.yy )
    {
        create_food();
        return true;
    }
    else
    {
        //if head moving right
        if(dir == "right")
        {
            if(snake[0].xx > lvl_width - 1)
            {
                game_over = true;
            }
        }
        else if(dir == "left")
        {
            if(snake[0].xx < 0)
            {
                game_over = true;
            }
        }
        else if(dir == "up")
        {
            if(snake[0].yy <= -1)
            {
                game_over = true;
            }
        }
        else if(dir = "down")
        {
            if(snake[0].yy >= lvl_height)
            {
                game_over = true;
            }
        }
         
        for(i = 2; i < snakeLen; i++)
        {
            if( (snake[0].xx == snake[i].xx) && (snake[0].yy == snake[i].yy) )
            {
                game_over = true;
                break;
            }
        }
         
        return false;
    }
}
 
setTimeout(function() {
animate();
}, 1000);
 
function moveSnake(e) 
{
    switch(e.keyCode) 
    {
        case 37:
            if(dir != "right")
            {
                dir = "left";
            }
            break;
        case 38:
            if(dir != "down")
            {
                dir = "up";
            }
            break;
        case 39:
            if(dir != "left")
            {
                dir = "right"; 
            }           
            break;
        case 40:
            if(dir != "up")
            {
                dir = "down";
            }
            break;  
    }   
}
 
function checkAllowMove(x, y)
{
    if(x < 32)
    {
        var x_index = 0;
    }
    else
    {
        var x_index = Math.round(x / 32);
    }
     
    if(y < 32)
    {
        var y_index = 19;
    }
    else
    {
        var y_index = (total_height / 32) - Math.round(y / 32);
    }
     
    if(level[x_index][y_index] == -1)
    {
        return true;
    }
    else
    {
        return false;
    }
}
 
function create_food()
{
    var x = 0;
    var y = 0;
    var recreate = false;
    do
    {
        recreate = false;
        x =  Math.floor((Math.random() * (lvl_width-1)));
        y =  Math.floor((Math.random() * (lvl_height-1)));
         
        for(i = 0; i < snakeLen; i++)
        {
            if( (snake[i].xx == x) && (snake[i].yy == y) )
            {
                recreate = true;
                break;
            }
        }
    }while(recreate == true);
    food = {xx: x, yy: y};
}
 
function create_snake()
{
    //var x =  Math.floor((Math.random() * (lvl_width-1)));
    //var y =  Math.floor((Math.random() * (lvl_height-1)));
    snake[0] = {xx: 4, yy: 1};
    snake[1] = {xx: 3, yy: 1};
    snake[2] = {xx: 2, yy: 1};
    snake[3] = {xx: 1, yy: 1};
    dir = "right";
}
 
function move_snake()
{
    var temp_x = 0;
    var temp_y = 0;
    var temp_xx = 0;
    var temp_yy = 0;
    var swap = true;
 
    //move snake forward
    for(var ii = 0; ii < snakeLen; ii++)
    {       
        if(ii == 0)
        {
            temp_x = snake[ii].xx;
            temp_y = snake[ii].yy;
 
            //if head moving right
            if(dir == "right")
            {
                snake[0] = {xx: (snake[0].xx + 1), yy: snake[0].yy};
            }
            else if(dir == "left")
            {
                snake[0] = {xx: (snake[0].xx - 1), yy: snake[0].yy};
            }
            else if(dir == "up")
            {
                snake[0] = {xx: snake[0].xx, yy: (snake[0].yy - 1)};
            }
            else if(dir = "down")
            {
                snake[0] = {xx: snake[0].xx, yy: (snake[0].yy + 1)};
            }
             
            if(checkSnakeCollide())
            {
                snake.push({xx: snake[(snake.length-1)].xx, yy: snake[(snake.length-1)].yy});
                snakeLen++;
            }
        }
        else
        {
            if(swap == true)
            {
                temp_xx = snake[ii].xx;
                temp_yy = snake[ii].yy;
                snake[ii] = {xx: temp_x, yy: temp_y};
 
                swap = false;
            }
            else
            {
                temp_x = snake[ii].xx;
                temp_y = snake[ii].yy;
                snake[ii] = {xx: temp_xx, yy: temp_yy};
                swap = true;
            }
        }
    }
 
}
 
function display()
{
     
    for(var i = 0; i < snakeLen; i++)
    {
        if(i == 0)
        {
            switch (dir)
            {
                case "left":
                    context.drawImage(snakeHeadImage, (snake[i].xx * 32), (snake[i].yy * 32) ); 
                    break;
                case "right":
                    drawRotatedImage(snakeHeadImage,(snake[i].xx * 32), (snake[i].yy * 32), 180);
                    break;
                case "up":
                    drawRotatedImage(snakeHeadImage,(snake[i].xx * 32), (snake[i].yy * 32), 90);
                    break;
                case "down":
                    drawRotatedImage(snakeHeadImage,(snake[i].xx * 32), (snake[i].yy * 32), 270);
                    break;
            }
        }
        else if(i == (snakeLen - 1) )
        {
            //following left
            if(snake[i].xx > snake[i-1].xx)
            {
                context.drawImage(snakeTailImage, (snake[i].xx * 32), (snake[i].yy * 32) ); 
            }
            //following right
            else if(snake[i].xx < snake[i-1].xx)
            {
                drawRotatedImage(snakeTailImage,(snake[i].xx * 32), (snake[i].yy * 32), 180);
            }
            //following up
            else if(snake[i].yy > snake[i-1].yy)
            {
                drawRotatedImage(snakeTailImage,(snake[i].xx * 32), (snake[i].yy * 32), 90);
            }
            //following down
            else if(snake[i].yy < snake[i-1].yy)
            {
                drawRotatedImage(snakeTailImage,(snake[i].xx * 32), (snake[i].yy * 32), 270);
            }
        }
        else
        {
            context.drawImage(snakeBodyImage, (snake[i].xx * 32), (snake[i].yy * 32) ); 
        }
 
    }
     
    context.drawImage(foodImage, (food.xx * 32), (food.yy * 32) ); 
 
}
 
function drawRotatedImage(image, x, y, angle) 
{ 
    var TO_RADIANS = Math.PI/180; 
 
    // save the current co-ordinate system 
    // before we screw with it
    context.save(); 
  
    // move to the middle of where we want to draw our image
    context.translate(x, y);
  
    // rotate around that point, converting our 
    // angle from degrees to radians 
    context.rotate(angle * TO_RADIANS);
  
    // draw it up and to the left by half the width
    // and height of the image 
    context.drawImage(image, -(image.width/2), -(image.height/2));
  
    // and restore the co-ords to how they were when we began
    context.restore(); 
}