package
{
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.events.MouseEvent;
 
    [SWF(width=600,height=600)]
    public class Game extends Sprite
    {
        private var _cellSize:int=20;
        private var _grid:Grid;
        private var _player:Sprite;
        private var _index:int;
        private var _path:Array;
 
        public function Game()
        {
            stage.align=StageAlign.TOP_LEFT;
            stage.scaleMode=StageScaleMode.NO_SCALE;
            makePlayer();
            makeGrid();
            stage.addEventListener(MouseEvent.CLICK, onGridClick);
        }
 
        /** 生成一个player角色(简单起见，就是一个圈) */
        private function makePlayer():void
        {
            _player=new Sprite();
            _player.graphics.beginFill(0xff0000);
            _player.graphics.drawCircle(0, 0, 5);
            _player.graphics.endFill();
            _player.x=Math.random() * 600;
            _player.y=Math.random() * 600;
            addChild(_player);
        }
 
        /** 生成网格，并随机放置一些障碍 */
        private function makeGrid():void
        {
            _grid=new Grid(30, 30);
            for (var i:int=0; i < 200; i++)
            {
                _grid.setWalkable(Math.floor(Math.random() * 30), Math.floor(Math.random() * 30), false);
            }
            drawGrid();
        }
 
        /** 画网格线以及为障碍物填充颜色*/
        private function drawGrid():void
        {
            graphics.clear();
            for (var i:int=0; i < _grid.numCols; i++)
            {
                for (var j:int=0; j < _grid.numRows; j++)
                {
                    var node:Node=_grid.getNode(i, j);
                    graphics.lineStyle(0);
                    graphics.beginFill(getColor(node));
                    graphics.drawRect(i * _cellSize, j * _cellSize, _cellSize, _cellSize);
                }
            }
        }
 
        /** 返回节点颜色 */
        private function getColor(node:Node):uint
        {
            if (!node.walkable)
                return 0;
            if (node == _grid.startNode)
                return 0xcccccc;
            if (node == _grid.endNode)
                return 0xff0000;
            return 0xffffff;
        }
 
        /** 鼠标点击时随机设置终点，并以player当前位置做为起点 */
        private function onGridClick(event:MouseEvent):void
        {
            var xpos:int=Math.floor(mouseX / _cellSize);
            var ypos:int=Math.floor(mouseY / _cellSize);
            _grid.setEndNode(xpos, ypos);
            xpos=Math.floor(_player.x / _cellSize);
            ypos=Math.floor(_player.y / _cellSize);
            _grid.setStartNode(xpos, ypos);
            drawGrid();
            findPath();
        }
 
        /** 寻路 */
        private function findPath():void
        {
            var astar:AStar=new AStar();
            if (astar.findPath(_grid))
            {
                _path=astar.path;
                _index=0;
                addEventListener(Event.ENTER_FRAME, onEnterFrame);
            }
        }
 
        /**每帧的动画处理*/
        private function onEnterFrame(event:Event):void
        {
            var targetX:Number=_path[_index].x * _cellSize + _cellSize / 2;
            var targetY:Number=_path[_index].y * _cellSize + _cellSize / 2;
             
            //把经过的点，涂上黄色
            var passedNode:Node=_path[_index];
            graphics.lineStyle(0);
            graphics.beginFill(0xffff00);
            graphics.drawRect(passedNode.x * _cellSize, passedNode.y * _cellSize, _cellSize, _cellSize);
             
            var dx:Number=targetX - _player.x;
            var dy:Number=targetY - _player.y;
            var dist:Number=Math.sqrt(dx * dx + dy * dy);
            if (dist < 1)
            {
                _index++;//索引加1，即取一个路径节点
                if (_index >= _path.length)//达到最后一个节点时，移除ENTER_FRAME监听
                {
                    removeEventListener(Event.ENTER_FRAME, onEnterFrame);
                }
            }
            else
            {
                _player.x+=dx * .5;
                _player.y+=dy * .5;
            }
        }
    }
}