import { Vec2 } from "cc";
//直线移动
export class Line2DMove {
    private _s:Vec2;//起始点
    private _e:Vec2;//终点
    private _percentSpeed:number;
    private _percentAddSpeed:number;
    private _percent:number;//进度
    private _current:Vec2;
    private _currentDir:Vec2;
     /**
     * 
     * @param start_x 起始点
     * @param start_y 
     * @param end_x 终点
     * @param end_y 
     * @param speed 速度
     * @param addSpeed 加速度
     */
    constructor(start_x:number,start_y:number,end_x:number,end_y:number,speed:number,addSpeed:number){
       this._s = new Vec2(start_x,start_y);
       this._e = new Vec2(end_x,end_y);
       this._current= new Vec2(start_x,start_y);
       this._currentDir=new Vec2(this._e.x-this._s.x,this._e.y-this._s.y).normalize();
       let dis = (new Vec2(end_x,end_y).subtract2f(start_x,start_y)).length(); 
       this._percent=0;
       this._percentSpeed= speed/dis;
       
       this._percentAddSpeed = addSpeed/dis;
    }
    public get target_pos_x():number{
        return this._e.x;
    }
    public get target_pos_y():number{
       return this._e.y;
    }
    public get current_dir():Vec2{
         return this._currentDir;
    }
    public get isEnd():boolean{
       return this._percent>=1;
    }
    /**
     * 向目标运动
     * @param dt 帧时间
     * @param mb 目标点，没有的话为初始定义的点
     * @returns 
     */
    public MoveTo(dt:number,mb:Vec2=null):Vec2{
       this._percentSpeed+=this._percentAddSpeed*dt;
       this._percent+=this._percentSpeed*dt;
       let nextpos = this.getPos(this._percent,this._s,mb==null ? this._e:mb);
       this._current.x=nextpos.x;
       this._current.y=nextpos.y;
       return this._current;
    }
    /**
      * 获取进度位置
      * @param t 当前时间进度 0-1
      * @param a 起点
      * @param b 控制点
      * @param c 终点
    */
    private _ab = new Vec2();
    private getPos(t:number,a:Vec2,b:Vec2):Vec2{
        Vec2.lerp(this._ab,a,b,t);
        return this._ab;
    }
}