tanqiu/assets/scripts/BulletControl/effects/BulletTrajectory.ts

import { _decorator, Component, Node, Vec3 } from 'cc';
import { BulletTrajectoryConfig } from '../BulletTypes';
const { ccclass } = _decorator;

/**
 * 弹道控制（可移植版）
 * - straight：匀速直线
 * - arc：带重力或弧线（简化为重力）
 * - guided：简单追踪（需要调用 setTarget 或外部提供方向更新）
 */
@ccclass('BCBulletTrajectory')
export class BulletTrajectory extends Component {
  private cfg: BulletTrajectoryConfig | null = null;
  private velocity: Vec3 = new Vec3(0, 0, 0);
  private target: Node | null = null;
  private homingTimer = 0;
  private origin: Vec3 = new Vec3();

  public init(cfg: BulletTrajectoryConfig, direction: Vec3, startPos: Vec3, originNode?: Node | null) {
    this.cfg = { ...cfg };
    const speed = Math.max(0, this.cfg.speed ?? 0);
    const dir = direction?.clone() ?? new Vec3(1, 0, 0);
    if (dir.length() === 0) dir.set(1, 0, 0);
    dir.normalize();
    this.velocity.set(dir.x * speed, dir.y * speed, 0);
    this.node.setPosition(startPos);
    this.origin.set(startPos);
    this.homingTimer = 0;
  }

  public setTarget(node: Node | null) {
    this.target = node;
  }

  public getCurrentVelocity(): Vec3 {
    return this.velocity.clone();
  }

  update(dt: number) {
    if (!this.cfg) return;
    const type = this.cfg.type;
    if (type === 'straight') {
      this.moveLinear(dt);
    } else if (type === 'arc') {
      this.moveArc(dt);
    } else if (type === 'guided') {
      this.moveGuided(dt);
    } else {
      this.moveLinear(dt);
    }
  }

  private moveLinear(dt: number) {
    const dx = this.velocity.x * dt;
    const dy = this.velocity.y * dt;
    const p = this.node.position;
    this.node.setPosition(p.x + dx, p.y + dy);
  }

  private moveArc(dt: number) {
    const g = this.cfg?.gravity ?? 0;
    // 简化：重力沿 y 轴正方向（向下）
    this.velocity.y -= g * dt;
    this.moveLinear(dt);
  }

  private moveGuided(dt: number) {
    const delay = Math.max(0, this.cfg?.homingDelay ?? 0);
    this.homingTimer += dt;
    if (this.homingTimer >= delay && this.target && this.target.isValid) {
      const pos = this.node.worldPosition;
      const tpos = this.target.worldPosition;
      const toTarget = new Vec3(tpos.x - pos.x, tpos.y - pos.y, 0);
      const dist = toTarget.length();
      if (dist > 1e-3) {
        toTarget.normalize();
        const strength = Math.max(0, Math.min(1, this.cfg?.homingStrength ?? 0));
        // 插值改变速度方向，但保持速率（magnitude）接近 cfg.speed
        const speed = Math.max(0, this.cfg?.speed ?? 0);
        const desired = new Vec3(toTarget.x * speed, toTarget.y * speed, 0);
        this.velocity.x = this.velocity.x + (desired.x - this.velocity.x) * strength;
        this.velocity.y = this.velocity.y + (desired.y - this.velocity.y) * strength;
      }
    }
    this.moveLinear(dt);
  }
}