using UnityEngine;

namespace BaseGames.Enemies
{
    /// <summary>
    /// 推进停滞检测：滑动窗口内的**净水平位移**不足阈值即判为停滞。
    /// 用于"命令了移动却推不动"的兜底（撞上未纳入检测层的碰撞体、贴墙微抖等）。
    ///
    /// <para>用净位移而非逐帧差值，避免"贴墙推进-被弹回"的微抖每帧重置计数。</para>
    /// <para><b>调用方须以字段持有本结构</b>（struct 的方法会就地修改字段）；
    /// 开始移动 / 更换目标后调用 <see cref="Reset"/> 重开窗口。</para>
    /// </summary>
    public struct StallDetector
    {
        private readonly float _windowSeconds;
        private readonly float _minProgress;
        private float _timer;
        private float _startX;
        private bool  _initialized;

        /// <param name="windowSeconds">判定窗口时长（秒）。</param>
        /// <param name="minProgress">窗口内所需的最小净位移（米）。</param>
        public StallDetector(float windowSeconds, float minProgress)
        {
            _windowSeconds = windowSeconds;
            _minProgress   = minProgress;
            _timer         = 0f;
            _startX        = 0f;
            _initialized   = false;
        }

        /// <summary>以当前位置重开窗口。</summary>
        public void Reset(float currentX)
        {
            _startX      = currentX;
            _timer       = 0f;
            _initialized = true;
        }

        /// <summary>
        /// 推进一帧。返回 true 表示本窗口内推进不足（停滞）；返回 true 后窗口自动以当前位置重开。
        /// </summary>
        public bool Tick(float currentX, float deltaTime)
        {
            if (!_initialized) { Reset(currentX); return false; }

            _timer += deltaTime;
            if (_timer < _windowSeconds) return false;

            bool stalled = Mathf.Abs(currentX - _startX) < _minProgress;
            _startX = currentX;
            _timer  = 0f;
            return stalled;
        }
    }
}