using UnityEngine;

namespace BaseGames.Enemies
{
    /// <summary>
    /// 敌人移动组件（架构 07_EnemyModule §3）。
    /// 实现：水平移动、面向目标、击退。
    /// ⚠️ 使用 Rigidbody2D.velocity（Unity 2022 LTS）。
    /// </summary>
    [RequireComponent(typeof(Rigidbody2D))]
    public class EnemyMovement : MonoBehaviour
    {
        [SerializeField] private EnemyStatsSO    _config;
        [SerializeField] private SpriteRenderer  _spriteRenderer;

        private Rigidbody2D _rb;
        private int _facingDir = 1;

        public bool IsGrounded { get; private set; }

        private void Awake()
        {
            Debug.Assert(_config != null, "[EnemyMovement] _config 未赋值，请在 Prefab Inspector 中指定 EnemyStatsSO。", this);
            _rb = GetComponent<Rigidbody2D>();
        }

        /// <summary>按 SO 配置速度水平移动。dir: +1 右 / -1 左 / 0 停止。</summary>
        public void MoveHorizontal(float dir)
        {
            float speed = _config.WalkSpeed;
            _rb.velocity = new Vector2(dir * speed, _rb.velocity.y);
            UpdateFacing(dir);
        }

        /// <summary>显式指定速度（BD 追击任务调用）。</summary>
        public void MoveWithSpeed(float dir, float speed)
        {
            _rb.velocity = new Vector2(dir * speed, _rb.velocity.y);
            UpdateFacing(dir);
        }

        public void FaceTarget(Vector2 targetPos)
        {
            float dir = targetPos.x < transform.position.x ? -1f : 1f;
            UpdateFacing(dir);
        }

        public void ApplyKnockback(Vector2 dir, float force)
        {
            _rb.velocity = dir.normalized * force;
        }

        public void StopHorizontal()
        {
            _rb.velocity = new Vector2(0f, _rb.velocity.y);
        }

        /// <summary>
        /// 向目标位置抖跃（抛物线累加填充）。
        /// 计算初速使尔子到达目标，用 Impulse 施加力。
        /// </summary>
        public void JumpToTarget(Vector2 target)
        {
            if (_rb == null) return;
            Vector2 delta     = target - (Vector2)transform.position;
            float   gravMag   = Mathf.Abs(Physics2D.gravity.y * _rb.gravityScale);
            float   timeAloft = Mathf.Max(0.1f, delta.x != 0f
                ? Mathf.Abs(delta.x) / _config.RunSpeed
                : 0.5f);

            float vy = (delta.y - 0.5f * (-gravMag) * timeAloft * timeAloft) / timeAloft;
            float vx = delta.x / timeAloft;

            _rb.velocity = new Vector2(vx, vy);
            UpdateFacing(vx);
        }

        private void UpdateFacing(float dir)
        {
            if (Mathf.Approximately(dir, 0f)) return;
            int newDir = dir > 0f ? 1 : -1;
            if (newDir == _facingDir) return;
            _facingDir = newDir;
            if (_spriteRenderer != null)
            {
                _spriteRenderer.flipX = newDir < 0;
            }
            else
            {
                // SpriteRenderer 未绑定时通过 localScale 翻转朝向
                Vector3 s = transform.localScale;
                transform.localScale = new Vector3(Mathf.Abs(s.x) * newDir, s.y, s.z);
            }
        }
    }
}