/**
    A class that display a repeating texture that can optionall be offset in either
	the x or y axis
    @author <a href="mailto:matthewcasperson@gmail.com">Matthew Casperson</a>
    @class
*/
function RepeatingGameObject()
{
    /** The width that the final image will take up
		@type Number
	*/
	this.width = 0;
	/** The height that the final image will take up
		@type Number
	*/
    this.height = 0;
	/** How much of the scrollX and scrollY to apply when drawing
		@type Number
	*/
    this.scrollFactor = 1;
	
    /**
        Initialises this object
        @return A reference to the initialised object
    */
    this.startupRepeatingGameObject = function(image, x, y, z, width, height, scrollFactor)
    {
        this.startupVisualGameObject(image, x, y, z);
        this.width = width;
        this.height = height;
        this.scrollFactor = scrollFactor;
        return this;
    }
	
    /**
        Clean this object up
    */
    this.shutdownstartupRepeatingGameObject = function()
    {
        this.shutdownVisualGameObject();
    }
    
	/**
        Draws this element to the back buffer
        @param dt Time in seconds since the last frame
		@param context The context to draw to
		@param xScroll The global scrolling value of the x axis  
		@param yScroll The global scrolling value of the y axis  
    */
    this.draw = function(dt, canvas, xScroll, yScroll)
    {
        var areaDrawn = [0, 0];
        
        for (var y = 0; y < this.height; y += areaDrawn[1])
        {
            for (var x = 0; x < this.width; x += areaDrawn[0])
            {
                // the top left corner to start drawing the next tile from
				var newPosition = [this.x + x, this.y + y];
				// the amount of space left in which to draw
                var newFillArea = [this.width - x, this.height - y];
				// the first time around you have to start drawing from the middle of the image
				// subsequent tiles alwyas get drawn from the top or left
                var newScrollPosition = [0, 0];
                if (x==0) newScrollPosition[0] = xScroll * this.scrollFactor;
                if (y==0) newScrollPosition[1] = yScroll * this.scrollFactor;
                areaDrawn = this.drawRepeat(canvas, newPosition, newFillArea, newScrollPosition);
            }
        }
    }
    
    this.drawRepeat = function(canvas, newPosition, newFillArea, newScrollPosition)
    {
        // find where in our repeating texture to start drawing (the top left corner)
        var xOffset = Math.abs(newScrollPosition[0]) % this.image.width;
        var yOffset = Math.abs(newScrollPosition[1]) % this.image.height;
        var left = newScrollPosition[0]<0?this.image.width-xOffset:xOffset;
        var top = newScrollPosition[1]<0?this.image.height-yOffset:yOffset;
        var width = newFillArea[0] < this.image.width-left?newFillArea[0]:this.image.width-left;
        var height = newFillArea[1] < this.image.height-top?newFillArea[1]:this.image.height-top;
        
        // draw the image
        canvas.drawImage(this.image, left, top, width, height, newPosition[0], newPosition[1], width, height);
        
        return [width, height];
    }
    
    
}
RepeatingGameObject.prototype = new VisualGameObject();