package lib.ui;

import kernel.ui.Pixel;
import lib.ui.Canvas;

/**
	Layer multiple canvases and compress them into one from a top down view.
**/
class CanvasStack {
	private var layers:Array<{c:Canvas, offset:Pos}> = [];
	private var width:Int = 0;
	private var hight:Int = 0;

	public function new() {}

	public function addLayer(c:Canvas, offset:Pos) {
		this.layers.push({c: c, offset: offset});

		var layerWidth = c.maxWidth() + offset.x;
		var layerHight = c.height() + offset.y;

		if (layerWidth > this.width) {
			this.width = layerWidth;
		}

		if (layerHight > this.hight) {
			this.hight = layerHight;
		}
	}

	public function compress():Canvas {
		var rtn = new Canvas();

		for (y in 0...this.hight) {
			for (x in 0...this.width) {
				var pos = new Pos({x: x, y: y});
				rtn.set(pos, this.pixelAt(pos));
			}
		}

		return rtn;
	}

	public function pixelAt(pos:Pos):Null<Pixel> {
		for (i in 0...this.layers.length) {
			var newi = (this.layers.length - 1) - i;
			var offset = this.layers[newi].offset;
			var px = this.layers[newi].c.get(pos - offset);
			if (px != null) {
				return px;
			}
		}

		return null;
	}
}