// assets/scripts/Preview.ts
import { _decorator, Component, Node, Prefab, instantiate, Vec3 } from "cc";
import { BallPhysics } from "./BallPhysics";
const { ccclass, property } = _decorator;

@ccclass("Preview")
export class Preview extends Component {
  @property(Prefab) pointPrefab: Prefab = null!;
  @property(Node) goal: Node = null!;

  @property({ tooltip: "轨迹点数量" }) maxPoints = 30;
  @property({ tooltip: "步长时间（秒）" }) timeStep = 0.05;

  @property(BallPhysics) ballPhys: BallPhysics = null!;

  private points: Node[] = [];

  clear() {
    for (const p of this.points) p.destroy();
    this.points.length = 0;
  }

  /** 显示预测轨迹 */
  showTrajectory(startPos: Vec3, dir: Vec3, speed: number, spin: Vec3) {
    this.clear();
    if (!this.pointPrefab || !this.ballPhys) return;

    const goalZ = this.goal?.worldPosition?.z;

    // 初始状态
    let pos = startPos.clone();
    let v = dir.clone().multiplyScalar(speed);
    let w = spin.clone(); // 自旋

    // 迭代预测
    // let age = 0;
    for (let i = 0; i < this.maxPoints; i++) {
      // age += this.timeStep;
      // 保存点
      const p = instantiate(this.pointPrefab);
      p.setWorldPosition(pos);
      p.setParent(this.node);
      this.points.push(p);

      // === 模拟 BallPhysics.update(dt) ===
      // const dt = this.timeStep;
      const dt = this.timeStep * 0.5;

      // 空气阻力
      const speedNow = v.length();
      if (speedNow > 0.01) {
        const drag = v.clone().multiplyScalar(-this.ballPhys.dragK * speedNow);
        v.add(drag.multiplyScalar(dt));
      }

      // 马格努斯效应：F = k * (ω × v)
      if (w.lengthSqr() > 0.0001 && v.lengthSqr() > 0.0001) {
        // const tFactor = 1.0 / (1.0 + age * 2.0); // age 是飞行时间，越久衰减越快
        // const magnus = w
        //   .clone()
        //   .cross(v)
        //   .multiplyScalar(this.ballPhys.magnusK * tFactor);
        // v.add(magnus.multiplyScalar(dt));
        const magnus = w.clone().cross(v).multiplyScalar(this.ballPhys.magnusK);
        v.add(magnus.multiplyScalar(dt));
      }

      // 重力
      v.y += -9.8 * dt;

      // 移动
      pos = pos.add(v.clone().multiplyScalar(dt));

      if (
        (startPos.z > goalZ && pos.z <= goalZ) ||
        (startPos.z < goalZ && pos.z >= goalZ)
      ) {
        break;
      }
    }
  }
}