using System.Collections.Generic;
using SLSUtilities.Feedback;
using Unity.Cinemachine;
using UnityEngine;

namespace Cielonos.MainGame.Effects.Feedback
{
    /// <summary>
    /// 单个位移震动实例的运行时状态。
    /// </summary>
    public class CameraPositionShakeInstance : ShakeInstanceBase
    {
        public FloatCurveChannel intensityCurve;
        public Vector3 amplitude;

        public CameraPositionShakeInstance(
            FeedbackTimeSettings timeSettings,
            IFeedbackTimeProvider timeProvider,
            FloatCurveChannel intensityCurve,
            Vector3 amplitude,
            float duration)
            : base(timeSettings, timeProvider, duration)
        {
            this.intensityCurve = intensityCurve;
            this.amplitude = amplitude;
        }

        /// <summary>
        /// 计算当前帧的偏移量。
        /// </summary>
        public Vector3 Evaluate()
        {
            float normalizedTime = duration > 0 ? timer / duration : 1f;
            float curveValue = intensityCurve.Evaluate(normalizedTime);
            return amplitude * curveValue;
        }
    }

    /// <summary>
    /// 摄像机位移震动事件，用于解耦 Action 与 Shaker。
    /// </summary>
    public struct CameraPositionShakeEvent
    {
        private static event ShakeDelegate OnEvent;

        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
        private static void RuntimeInitialization() { OnEvent = null; }

        public delegate void ShakeDelegate(
            FeedbackContext feedbackContext,
            FloatCurveChannel intensityCurve,
            Vector3 amplitude,
            bool stop
        );

        public static void Register(ShakeDelegate callback) { OnEvent += callback; }
        public static void Unregister(ShakeDelegate callback) { OnEvent -= callback; }

        public static void Trigger(
            FeedbackContext feedbackContext,
            FloatCurveChannel intensityCurve,
            Vector3 amplitude,
            bool stop = false)
        {
            OnEvent?.Invoke(feedbackContext, intensityCurve, amplitude, stop);
        }
    }
    
    /// <summary>
    /// Cinemachine 位移震动器。挂载于 CinemachineCamera 上，
    /// 监听 CameraPositionShakeEvent，驱动 CinemachineCameraOffset 实现叠加震动。
    /// </summary>
    [AddComponentMenu("Cielonos/Feedback Shakers/Camera Position Shaker")]
    [RequireComponent(typeof(CinemachineCamera))]
    [RequireComponent(typeof(CinemachineCameraOffset))]
    public class CinemachinePositionShaker : MonoBehaviour
    {
        private CinemachineCameraOffset _offsetComponent;
        private Vector3 _initialOffset;
        private readonly List<CameraPositionShakeInstance> _activeShakes = new List<CameraPositionShakeInstance>();

        private void Awake()
        {
            _offsetComponent = GetComponent<CinemachineCameraOffset>();
            _initialOffset = _offsetComponent.Offset;
        }

        private void OnEnable()
        {
            CameraPositionShakeEvent.Register(OnShakeEvent);
        }

        private void OnDisable()
        {
            CameraPositionShakeEvent.Unregister(OnShakeEvent);
            StopAll();
        }

        private void Update()
        {
            if (_offsetComponent == null) return;

            if (_activeShakes.Count == 0)
            {
                _offsetComponent.Offset = _initialOffset;
                return;
            }
            
            Vector3 totalOffset = Vector3.zero;

            for (int i = _activeShakes.Count - 1; i >= 0; i--)
            {
                CameraPositionShakeInstance shake = _activeShakes[i];
                shake.Tick();
                totalOffset += shake.Evaluate();

                if (shake.IsFinished)
                {
                    _activeShakes.RemoveAt(i);
                }
            }

            _offsetComponent.Offset = _initialOffset + totalOffset;
        }

        private void OnShakeEvent(
            FeedbackContext feedbackContext,
            FloatCurveChannel intensityCurve,
            Vector3 amplitude,
            bool stop)
        {
            if (stop) { StopAll(); return; }

            var instance = new CameraPositionShakeInstance(
                feedbackContext.timeSettings,
                feedbackContext.player.TimeProvider,
                intensityCurve,
                amplitude,
                feedbackContext.duration
            );
            _activeShakes.Add(instance);
        }

        private void StopAll()
        {
            _activeShakes.Clear();
            if (_offsetComponent != null)
            {
                _offsetComponent.Offset = _initialOffset;
            }
        }
    }
}