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

namespace Cielonos.MainGame.Effects.Feedback
{
    /// <summary>
    /// 单个FOV震动实例的运行时状态。
    /// </summary>
    public class CameraFovShakeInstance : ShakeInstanceBase
    {
        public FloatCurveChannel fovCurve;

        public CameraFovShakeInstance(FeedbackTimeSettings timeSettings, IFeedbackTimeProvider timeProvider, 
            FloatCurveChannel fovCurve, float duration) : base(timeSettings, timeProvider, duration)
        {
            this.fovCurve = fovCurve;
        }
    }

    /// <summary>
    /// 摄像机视野角(FOV)震动事件，用于解耦 Action 与 Shaker。
    /// </summary>
    public struct CameraFovShakeEvent
    {
        private static event ShakeDelegate OnEvent;

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

        public delegate void ShakeDelegate(
            FeedbackContext feedbackContext,
            FloatCurveChannel fovCurve,
            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 fovCurve,
            bool stop = false)
        {
            OnEvent?.Invoke(feedbackContext, fovCurve, stop);
        }
    }

    /// <summary>
    /// CinemachineCamera FOV 震动聚合器。挂载于 CinemachineCamera 上，
    /// 监听 CameraFovShakeEvent，叠加驱动 Lens.FieldOfView。
    /// </summary>
    [AddComponentMenu("Cielonos/Feedback Shakers/Camera FOV Shaker")]
    [RequireComponent(typeof(CinemachineCamera))]
    public class CameraFovShaker : MonoBehaviour
    {
        private CinemachineCamera _camera;
        public float initialFov;
        private readonly List<CameraFovShakeInstance> _activeShakes = new List<CameraFovShakeInstance>();

        private void Awake()
        {
            _camera = GetComponent<CinemachineCamera>();
            initialFov = _camera.Lens.FieldOfView;
        }

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

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

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

            if (_activeShakes.Count == 0)
            {
                SetFov(initialFov);
                return;
            }
            
            float additiveFov = 0f;
            float absoluteFov = 0f;
            bool hasAbsolute = false;

            for (int i = _activeShakes.Count - 1; i >= 0; i--)
            {
                CameraFovShakeInstance shake = _activeShakes[i];
                shake.Tick();
                float normalizedTime = shake.timer / shake.duration;
                
                if (shake.fovCurve.relativeToInitial)
                {
                    additiveFov += shake.fovCurve.Evaluate(normalizedTime);
                }
                else
                {
                    absoluteFov = shake.fovCurve.Evaluate(normalizedTime);
                    hasAbsolute = true;
                }

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

            float finalFov = hasAbsolute ? absoluteFov : initialFov + additiveFov;
            SetFov(finalFov);
        }

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

            var instance = new CameraFovShakeInstance(
                feedbackContext.timeSettings,
                feedbackContext.player.TimeProvider,
                fovCurve,
                feedbackContext.duration
            );
            _activeShakes.Add(instance);
        }

        private void SetFov(float fov)
        {
            LensSettings lens = _camera.Lens;
            lens.FieldOfView = fov;
            _camera.Lens = lens;
        }

        private void StopAll()
        {
            _activeShakes.Clear();
            if (_camera != null)
            {
                SetFov(initialFov);
            }
        }
    }
}