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
   * 起点终点一致时没有速度将不起作用
   */
   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();
      if (dis <= 0) {
         this._percent = 1;
         this._percentSpeed = 0;
         this._percentAddSpeed = 0;
      } else {
         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;
   }
   public get percent(): number {
      return this._percent;
   }
   /**
    * 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 {
      if (this._percentSpeed == 0 && this._percentAddSpeed == 0) return this._current;
      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;
   }
}