tanqiu/assets/scripts/CombatSystem/BulletEffects/BulletTrajectory.ts

import { _decorator, Component, Node, Vec2, Vec3, RigidBody2D, find } from 'cc';
const { ccclass, property } = _decorator;

/**
 * 弹道控制器
 * 负责控制子弹的运动轨迹
 */

export interface BulletTrajectoryConfig {
    type: 'straight' | 'parabolic' | 'homing' | 'arc';  // 弹道类型
    speed: number;                                      // 初始速度
    gravity: number;                                    // 重力影响 (arc/straight 可为0)
    homingStrength: number;                             // 追踪强度 (0-1)
    homingDelay: number;                                // 追踪延迟（秒）
    /**
     * 旋转速率 (0~1)。仅在 arc 弹道中使用，值越大转向越快。
     */
    rotateSpeed?: number;
}

export interface TrajectoryState {
    initialVelocity: Vec3;     // 初始速度
    currentVelocity: Vec3;     // 当前速度
    startPosition: Vec3;       // 起始位置
    targetPosition?: Vec3;     // 目标位置（追踪用）
    elapsedTime: number;       // 经过时间
    phase: 'launch' | 'homing' | 'return';  // 运动阶段
}

@ccclass('BulletTrajectory')
export class BulletTrajectory extends Component {
    private config: BulletTrajectoryConfig = null;
    private state: TrajectoryState = null;
    private rigidBody: RigidBody2D = null;
    private targetNode: Node = null;
    private homingTimer: number = 0;
    
    // === Arc Trajectory ===
    private arcDir: Vec3 = null;          // 当前方向
    private arcTargetDir: Vec3 = null;    // 目标方向（最终方向）
    
    /**
     * 初始化弹道
     */
    public init(config: BulletTrajectoryConfig, direction: Vec3, startPos: Vec3) {
        this.config = { ...config };
        this.rigidBody = this.getComponent(RigidBody2D);
        
        if (!this.rigidBody && config.type !== 'arc') {
            return;
        }
        
        // 初始化状态
        this.state = {
            initialVelocity: direction.clone().multiplyScalar(config.speed),
            currentVelocity: direction.clone().multiplyScalar(config.speed),
            startPosition: startPos.clone(),
            elapsedTime: 0,
            phase: 'launch'
        };
        
        this.homingTimer = config.homingDelay;
        
        // 设置初始速度
        this.applyInitialVelocity();
        
        // 寻找目标（用于追踪弹道）
        if (config.type === 'homing') {
            this.findTarget();
        }
    }
    
    /**
     * 设置初始速度
     */
    private applyInitialVelocity() {
        switch (this.config.type) {
            case 'straight':
                this.rigidBody.linearVelocity = new Vec2(
                    this.state.initialVelocity.x,
                    this.state.initialVelocity.y
                );
                break;
                
            case 'parabolic':
                // 计算抛物线初始速度
                const velocity = this.calculateParabolicVelocity();
                this.rigidBody.linearVelocity = velocity;
                this.state.currentVelocity.set(velocity.x, velocity.y, 0);
                break;
                
            case 'homing':
                this.rigidBody.linearVelocity = new Vec2(
                    this.state.initialVelocity.x,
                    this.state.initialVelocity.y
                );
                break;
                
            case 'arc':
                // 计算带 45° 随机偏移的初始方向
                const baseDir = this.state.initialVelocity.clone().normalize();
                const sign = Math.random() < 0.5 ? 1 : -1;
                const rad = 45 * Math.PI / 180 * sign;
                const cos = Math.cos(rad);
                const sin = Math.sin(rad);
                const offsetDir = new Vec3(
                    baseDir.x * cos - baseDir.y * sin,
                    baseDir.x * sin + baseDir.y * cos,
                    0
                ).normalize();

                this.arcDir = offsetDir;
                this.arcTargetDir = baseDir;

                // 如果有物理组件，则设置线速度；否则后续 updateArcTrajectory 将直接操作位移
                if (this.rigidBody) {
                    this.rigidBody.linearVelocity = new Vec2(offsetDir.x * this.config.speed, offsetDir.y * this.config.speed);
                }
                // 保存当前速度
                this.state.currentVelocity.set(offsetDir.x * this.config.speed, offsetDir.y * this.config.speed, 0);
                break;
        }
    }
    
    /**
     * 计算抛物线初始速度
     */
    private calculateParabolicVelocity(): Vec2 {
        // NOTE:
        // 1. 当目标位于子弹正上/下方时, 原 direction 的 x 分量可能非常小甚至为 0, 导致 vx≈0, 子弹会几乎垂直运动, 看起来像"钢球"直落。
        // 2. 对于抛物线弹道, 我们总是希望子弹具备一个最小的水平速度, 并且保证初速度向上( vy>0 ),
        //    这样才能形成明显的抛物线效果并最终击中目标。

        const rawDir = this.state.initialVelocity.clone().normalize();

        // 单独提取水平方向, 忽略原始 y 分量, 以保证抛物线始终向前飞行
        const horizontalDir = new Vec3(rawDir.x, 0, 0);

        // 若水平方向过小, 取发射者面朝方向 (rawDir.x 的符号) 作为水平单位向量
        if (Math.abs(horizontalDir.x) < 0.01) {
            horizontalDir.x = rawDir.x >= 0 ? 1 : -1;
        }
        horizontalDir.normalize();

        const speed = this.config.speed;

        // 基础水平速度 (保持恒定, 不受重力影响)
        const vx = horizontalDir.x * speed;

        // 计算纵向初速度, 使得理论最高点接近 arcHeight
        // vy = sqrt(2 * g * h)
        const g = Math.max(0.1, Math.abs(this.config.gravity * 9.8)); // 避免 g=0 导致除0或 vy=0
        const desiredHeight = Math.max(1, 20); // 使用固定高度20作为默认抛物线高度
        let vy = Math.sqrt(2 * g * desiredHeight);

        // 如果原始方向有明显的向上分量, 为了兼容旧配置, 适当叠加
        if (rawDir.y > 0.1) {
            vy += rawDir.y * speed * 0.5; // 50% 叠加, 防止过高
        }

        return new Vec2(vx, vy);
    }
    
    /**
     * 寻找追踪目标
     */
    private findTarget() {
        const enemyContainer = find('Canvas/GameLevelUI/enemyContainer');
        if (!enemyContainer) return;
        
        const enemies = enemyContainer.children.filter(child => 
            child.active && this.isEnemyNode(child)
        );
        
        if (enemies.length === 0) return;
        
        // 寻找最近的敌人
        let nearestEnemy: Node = null;
        let nearestDistance = Infinity;
        const bulletPos = this.node.worldPosition;
        
        for (const enemy of enemies) {
            const distance = Vec3.distance(bulletPos, enemy.worldPosition);
            if (distance < nearestDistance) {
                nearestDistance = distance;
                nearestEnemy = enemy;
            }
        }
        
        if (nearestEnemy) {
            this.targetNode = nearestEnemy;
            this.state.targetPosition = nearestEnemy.worldPosition.clone();
        }
    }
    
    /**
     * 判断是否为敌人节点
     */
    private isEnemyNode(node: Node): boolean {
        const name = node.name.toLowerCase();
        return name.includes('enemy') || 
               name.includes('敌人') ||
               node.getComponent('EnemyInstance') !== null;
    }
    
    update(dt: number) {
        if (!this.config || !this.state) return;
        
        this.state.elapsedTime += dt;
        
        switch (this.config.type) {
            case 'straight':
                this.updateStraightTrajectory(dt);
                break;
            case 'parabolic':
                this.updateParabolicTrajectory(dt);
                break;
            case 'homing':
                this.updateHomingTrajectory(dt);
                break;
            case 'arc':
                this.updateArcTrajectory(dt);
                break;
        }
    }
    
    /**
     * 更新直线弹道
     */
    private updateStraightTrajectory(dt: number) {
        // 直线弹道保持恒定速度，主要由物理引擎处理
        const currentVel = this.rigidBody.linearVelocity;
        const targetSpeed = this.config.speed;
        
        // 确保速度保持恒定
        const currentSpeed = Math.sqrt(currentVel.x * currentVel.x + currentVel.y * currentVel.y);
        if (Math.abs(currentSpeed - targetSpeed) > 1) {
            const direction = new Vec2(currentVel.x, currentVel.y).normalize();
            this.rigidBody.linearVelocity = direction.multiplyScalar(targetSpeed);
        }
    }
    
    /**
     * 更新抛物线弹道
     */
    private updateParabolicTrajectory(dt: number) {
        // 应用重力影响
        const currentVel = this.rigidBody.linearVelocity;
        const gravityForce = this.config.gravity * 9.8 * dt;
        
        this.rigidBody.linearVelocity = new Vec2(
            currentVel.x,
            currentVel.y - gravityForce
        );
        
        this.state.currentVelocity.set(currentVel.x, currentVel.y - gravityForce, 0);
    }
    
    /**
     * 更新追踪弹道
     */
    private updateHomingTrajectory(dt: number) {
        // 追踪延迟后开始追踪
        if (this.homingTimer > 0) {
            this.homingTimer -= dt;
            return;
        }

        // 确定追踪目标位置（敌人节点 or 返回点）
        let targetPos: Vec3 = null;

        if (this.state.phase === 'return' && this.state.targetPosition) {
            // 回程阶段，使用存储的返回坐标
            targetPos = this.state.targetPosition;
        } else {
            // 主动追踪敌人
            if (!this.targetNode || !this.targetNode.isValid) {
                this.findTarget();
            }
            if (this.targetNode && this.targetNode.isValid) {
                targetPos = this.targetNode.worldPosition;
            }
        }

        // 若依旧没有目标，直接退出
        if (!targetPos) {
            return;
        }

        // 计算追踪力
        const currentPos = this.node.worldPosition;
        const direction = targetPos.clone().subtract(currentPos).normalize();
        
        // 获取当前速度
        const currentVel = this.rigidBody.linearVelocity;
        const currentVelVec3 = new Vec3(currentVel.x, currentVel.y, 0);
        
        // 线性插值追踪
        const homingForce = this.config.homingStrength * dt * 10;
        const targetVelocity = direction.multiplyScalar(this.config.speed);
        
        const newVelocity = currentVelVec3.lerp(targetVelocity, homingForce);
        
        this.rigidBody.linearVelocity = new Vec2(newVelocity.x, newVelocity.y);
        this.state.currentVelocity.set(newVelocity);
    }
    
    /**
     * 更新弧线弹道
     */
    private updateArcTrajectory(dt: number) {
        if (!this.arcDir || !this.arcTargetDir) return;

        // === 动态追踪目标 ===
        // 若当前没有有效目标，则尝试重新寻找
        if (!this.targetNode || !this.targetNode.isValid) {
            this.findTarget();
        }

        // 每帧计算目标方向，使得弹道持续朝向敌人
        if (this.targetNode && this.targetNode.isValid) {
            const pos = this.node.worldPosition;
            const dirToTarget = this.targetNode.worldPosition.clone().subtract(pos).normalize();
            this.arcTargetDir.set(dirToTarget);
        }

        // 根据与目标距离动态调整转向速率：越近转得越快，避免打圈
        let rotateFactor = (this.config.rotateSpeed ?? 0.5) * dt;
        if (this.targetNode && this.targetNode.isValid) {
            const distance = Vec3.distance(this.node.worldPosition, this.targetNode.worldPosition);
            rotateFactor *= (2000 / Math.max(distance, 50));
        }

        const newDir = new Vec3();
        Vec3.slerp(newDir, this.arcDir, this.arcTargetDir, Math.min(1, rotateFactor));
        this.arcDir.set(newDir);

        // 更新位移 / 速度
        if (this.rigidBody) {
            this.rigidBody.linearVelocity = new Vec2(this.arcDir.x * this.config.speed, this.arcDir.y * this.config.speed);
        } else {
            const displacement = this.arcDir.clone().multiplyScalar(this.config.speed * dt);
            this.node.worldPosition = this.node.worldPosition.add(displacement);
        }

        // 更新状态中的当前速度
        this.state.currentVelocity.set(this.arcDir.x * this.config.speed, this.arcDir.y * this.config.speed, 0);
    }
    
    /**
     * 获取当前速度
     */
    public getCurrentVelocity(): Vec3 {
        if (this.config?.type === 'arc') {
            return this.arcDir ? this.arcDir.clone().multiplyScalar(this.config.speed) : new Vec3();
        }

        const vel = this.rigidBody?.linearVelocity;
        if (!vel) return new Vec3();
        return new Vec3(vel.x, vel.y, 0);
    }
    
    /**
     * 获取弹道状态
     */
    public getState(): TrajectoryState {
        return this.state;
    }
    
    /**
     * 设置新的目标位置（用于回旋镖等）
     */
    public setTargetPosition(target: Vec3) {
        this.state.targetPosition = target.clone();
    }
    
    /**
     * 反转方向（用于回旋镖）
     */
    public reverseDirection() {
        const currentVel = this.rigidBody.linearVelocity;
        this.rigidBody.linearVelocity = new Vec2(-currentVel.x, -currentVel.y);
        this.state.currentVelocity.multiplyScalar(-1);
        this.state.phase = 'return';
    }
    
    /**
     * 改变方向（用于弹射）
     */
    public changeDirection(newDirection: Vec3) {
        // 归一化新方向
        const normalizedDir = newDirection.clone().normalize();
        
        // 保持当前速度大小
        const currentSpeed = this.config.speed;
        
        // 更新速度
        this.rigidBody.linearVelocity = new Vec2(
            normalizedDir.x * currentSpeed,
            normalizedDir.y * currentSpeed
        );
        
        // 更新状态
        this.state.currentVelocity.set(normalizedDir.x * currentSpeed, normalizedDir.y * currentSpeed, 0);
    }
    
    /**
     * 设置重力
     */
    public setGravity(gravity: number) {
        this.config.gravity = gravity;
    }
    
    /**
     * 验证配置
     */
    public static validateConfig(config: BulletTrajectoryConfig): boolean {
        if (!config) return false;
        
        if (config.speed <= 0) return false;
        if (config.gravity < 0) return false;
        if (config.homingStrength < 0 || config.homingStrength > 1) return false;
        if (config.homingDelay < 0) return false;
        if (config.rotateSpeed !== undefined && (config.rotateSpeed < 0 || config.rotateSpeed > 1)) return false;
        
        return true;
    }
}