(function(ns){

var Holdbacks = ns.Holdbacks = Hilo.Class.create({
    Extends: Hilo.Container,
    constructor: function(properties){
        Holdbacks.superclass.constructor.call(this, properties);
        
        //管子之间的水平间隔
        this.hoseSpacingX = 300;
        //上下管子之间的垂直间隔，即小鸟要穿越的空间大小
        this.hoseSpacingY = 290;
        //管子的总数（上下一对管子算一个）
        this.numHoses = 4;
        //移出屏幕左侧的管子数量，一般设置为管子总数的一半
        this.numOffscreenHoses = this.numHoses * 0.5;
        //管子的宽度（包括管子之间的间隔）
        this.hoseWidth = 148 + this.hoseSpacingX;

        //初始化障碍的宽和高
        this.width = this.hoseWidth * this.numHoses;
        this.height = properties.height;

        this.reset();
        this.createHoses(properties.image);
        this.moveTween = new Hilo.Tween(this, null, {
            onComplete: this.resetHoses.bind(this)
        });
    },

    startX: 0, //障碍开始的起始x轴坐标
    groundY: 0, //地面的y轴坐标

    hoseSpacingX: 0, //管子之间的水平间隔
    hoseSpacingY: 0, //上下管子之间的垂直间隔
    numHoses: 0, //管子的总数（上下一对管子算一个）
    numOffscreenHoses: 0, //移出屏幕左侧的管子数量
    hoseWidth: 0, //管子的宽度（包括管子之间的间隔）

    passThrough: 0, //穿过的管子的数量，也即移出屏幕左侧的管子的数量

    createHoses: function(image){
        for(var i = 0; i < this.numHoses; i++){
            var downHose = new Hilo.Bitmap({
                id: 'down' + i,
                image: image,
                rect: [0, 0, 148, 820],
                boundsArea:[
                    {x:8, y:0}, 
                    {x:140, y:0}, 
                    {x:140, y:60}, 
                    {x:136, y:60}, 
                    {x:136, y:820}, 
                    {x:14, y:820}, 
                    {x:14, y:60}, 
                    {x:8, y:60}
                ]
            }).addTo(this);

            var upHose = new Hilo.Bitmap({
                id: 'up' + i,
                image: image,
                rect: [148, 0, 148, 820],
                boundsArea:[
                    {x:14, y:0}, 
                    {x:140, y:0}, 
                    {x:140, y:820-60}, 
                    {x:144, y:820-60},
                    {x:144, y:820}, 
                    {x:8, y:820}, 
                    {x:8, y:820-60}, 
                    {x:14, y:820-60}
                ]
            }).addTo(this);

            this.placeHose(downHose, upHose, i);
        }           
    },

    placeHose: function(down, up, index){
        //下面障碍在y轴的最上的位置
        var downMinY = this.groundY - down.height + this.hoseSpacingY;
        //下面障碍在y轴的最下的位置
        var downMaxY = this.groundY - 180;
        //在downMinY和downMaxY之间随机位置
        down.y = downMinY + (downMaxY - downMinY) * Math.random() >> 0;
        down.x = this.hoseWidth * index;

        up.y = down.y - this.hoseSpacingY - up.height;
        up.x = down.x;
    },

    resetHoses: function(){
        var total = this.children.length;

        //把已移出屏幕外的管子放到队列最后面，并重置它们的可穿越位置
        for(var i = 0; i < this.numOffscreenHoses; i++){
            var downHose = this.getChildAt(0);
            var upHose = this.getChildAt(1);
            this.setChildIndex(downHose, total - 1);
            this.setChildIndex(upHose, total - 1);
            this.placeHose(downHose, upHose, this.numOffscreenHoses + i);
        }
        
        //重新确定队列中所有管子的x轴坐标
        for(var i = 0; i < total - this.numOffscreenHoses * 2; i++){
            var hose = this.getChildAt(i);
            hose.x = this.hoseWidth * (i * 0.5 >> 0);
        }

        //重新确定障碍的x轴坐标
        this.x = 0;

        //更新穿过的管子数量
        this.passThrough += this.numOffscreenHoses;

        //继续移动
        this.startMove();
        Hilo.Tween._tweens.push(this.moveTween);
    },

    startMove: function(){
        //设置缓动的x轴坐标
        var targetX = -this.hoseWidth * this.numOffscreenHoses;
        //设置缓动时间
        this.moveTween.duration = (this.x - targetX) * 4;
        //设置缓动的变换属性，即x从当前坐标变换到targetX
        this.moveTween.setProps({x:this.x}, {x:targetX});
        //启动缓动动画
        this.moveTween.start();
    },

    stopMove: function(){
        if(this.moveTween) this.moveTween.pause();
    },

    checkCollision: function(bird){
        for(var i = 0, len = this.children.length; i < len; i++){
            if(bird.hitTestObject(this.children[i], true)){
                return true;
            }
        }
        return false;
    },

    calcPassThrough: function(x){
        var count = 0;

        x = -this.x + x;
        if(x > 0){
            var num = x / this.hoseWidth + 0.5 >> 0;
            count += num;
        }
        count += this.passThrough;

        return count;
    },

    reset: function(){
        this.x = this.startX;
        this.passThrough = 0;
    }
    
});

})(window.game);