using UnityEngine;
using Unity.Cinemachine;
using BaseGames.Core;

namespace BaseGames.Camera
{
    /// <summary>
    /// 相机状态单例控制器。须放置在 Persistent 场景中。
    ///
    /// 支持两种相机切换模式：
    ///   1. 全局双 VCam 模式（推荐）：<see cref="SwitchArea"/>
    ///      两台全局 CinemachineCamera（<c>_vcamA</c> / <c>_vcamB</c>）交替承接各区域，
    ///      通过优先级 ping-pong 触发 Cinemachine 混合过渡。场景内无需每个区域都放置 VCam。
    ///
    ///   2. 专有 VCam 模式：<see cref="SwitchArea"/>（区域含 dedicatedCamera 时自动使用）
    ///      激活该区域专属的 CinemachineCamera（优先级 > 全局 VCam），
    ///      适用于需要独特相机参数的特殊区域。
    /// </summary>
    [DefaultExecutionOrder(-100)]
    public class CameraStateController : MonoBehaviour, ICameraService
    {
        [Header("引用")]
        [SerializeField] private CinemachineBrain         _brain;
        [SerializeField] private CinemachineImpulseSource _impulseSource;

        [Header("全局双 VCam（Persistent 场景中放置两台通用虚拟相机）")]
        [Tooltip("两台 VCam 交替承接各相机区域，通过优先级 ping-pong 触发混合过渡。\n" +
                 "须各自挂载 CinemachineCamera + CinemachineConfiner2D；\n" +
                 "Follow 指向 Player/CameraFollowTarget（或运行时调用 SetFollowTarget 赋值）。")]
        [SerializeField] private CinemachineCamera _vcamA;
        [SerializeField] private CinemachineCamera _vcamB;

        [Tooltip("全局 VCam 激活时的优先级（非活跃时为 0）。专有 VCam 的 _dedicatedPriority 须高于此值。")]
        [SerializeField] private int _globalActivePriority = 10;

        [Header("默认混合配置")]
        [SerializeField] private CameraBlendProfileSO _defaultBlendProfile;

        // ── 状态 ──────────────────────────────────────────────────────────────
        private int                   _activeSlot        = -1; // -1 = 未初始化；0 = A；1 = B
        private CinemachineCamera     _activeDedicatedCam;
        private CinemachineConfiner2D _confinerA;
        private CinemachineConfiner2D _confinerB;

        // ── Lifecycle ────────────────────────────────────────────────────────

        private void Awake()
        {
            if (ServiceLocator.GetOrDefault<ICameraService>() != null) { Destroy(gameObject); return; }
            ServiceLocator.Register<ICameraService>(this);

            // 缓存 Confiner 引用
            if (_vcamA != null) _confinerA = _vcamA.GetComponent<CinemachineConfiner2D>();
            if (_vcamB != null) _confinerB = _vcamB.GetComponent<CinemachineConfiner2D>();

            // 初始两台 VCam 均处于非活跃优先级
            if (_vcamA != null) _vcamA.Priority = 0;
            if (_vcamB != null) _vcamB.Priority = 0;
        }

        private void OnDestroy()
        {
            ServiceLocator.Unregister<ICameraService>(this);
        }

        // ── 公开 API ──────────────────────────────────────────────────────────

        /// <summary>
        /// 切换到目标相机区域。
        /// <list type="bullet">
        ///   <item>区域有专有 VCam → 激活它（高优先级），全局 VCam 保持当前状态。</item>
        ///   <item>区域无专有 VCam → 配置非活跃全局 VCam，ping-pong 切换优先级触发混合。</item>
        /// </list>
        /// </summary>
        public void SwitchArea(CameraArea targetArea)
        {
            if (targetArea == null) return;

            ApplyBlendProfile(targetArea.BlendProfile ?? _defaultBlendProfile);

            if (targetArea.HasDedicated)
                ActivateDedicated(targetArea);
            else
                ActivateGlobalSlot(targetArea);
        }

        /// <summary>
        /// 运行时为两台全局 VCam 统一设置跟随目标（如 Player/CameraFollowTarget）。
        /// 可在 Player 生成后由任意系统调用。
        /// </summary>
        public void SetFollowTarget(Transform followTarget)
        {
            if (_vcamA != null) _vcamA.Follow = followTarget;
            if (_vcamB != null) _vcamB.Follow = followTarget;
        }

        /// <summary>触发屏幕抖动。</summary>
        public void TriggerImpulse(Vector3 velocity)
        {
            if (_impulseSource != null) _impulseSource.GenerateImpulse(velocity);
        }

        /// <summary>以默认强度触发屏幕抖动。</summary>
        public void TriggerImpulse(float strength = 0.3f)
            => TriggerImpulse(Vector3.down * strength);

        // ── 内部方法 ──────────────────────────────────────────────────────────

        /// <summary>激活区域的专有 VCam（高优先级）。</summary>
        private void ActivateDedicated(CameraArea area)
        {
            // 降低前一个专有 VCam（若与新的不同）
            if (_activeDedicatedCam != null && _activeDedicatedCam != area.DedicatedCamera)
                _activeDedicatedCam.Priority = 0;

            _activeDedicatedCam          = area.DedicatedCamera;
            _activeDedicatedCam.Priority = area.DedicatedPriority;
        }

        /// <summary>
        /// 使用全局 VCam ping-pong 切换到新区域。
        /// 配置非活跃 VCam 的 Confiner → 提升其优先级 → 降低旧 VCam 优先级。
        /// Cinemachine Brain 检测到优先级变化后自动触发混合。
        /// </summary>
        private void ActivateGlobalSlot(CameraArea area)
        {
            // 收回专有 VCam
            if (_activeDedicatedCam != null)
            {
                _activeDedicatedCam.Priority = 0;
                _activeDedicatedCam = null;
            }

            bool noVCams = _vcamA == null && _vcamB == null;
            if (noVCams)
            {
                Debug.LogWarning("[CameraStateController] 全局 VCam A / B 均未绑定，无法切换相机区域。");
                return;
            }

            // 首次调用：直接激活 VCamA（场景淡入阶段，无需混合动画）
            if (_activeSlot < 0)
            {
                var cam     = _vcamA ?? _vcamB;
                var confiner = _vcamA != null ? _confinerA : _confinerB;
                ConfigureSlot(cam, confiner, area);
                cam.Priority = _globalActivePriority;
                _activeSlot  = _vcamA != null ? 0 : 1;
                return;
            }

            // Ping-pong：配置非活跃槽 → 升级其优先级 → 降低活跃槽优先级
            bool nextIsA         = _activeSlot != 0;
            var  inactiveCam     = nextIsA ? _vcamA : _vcamB;
            var  activeCam       = nextIsA ? _vcamB : _vcamA;
            var  inactiveConfiner = nextIsA ? _confinerA : _confinerB;

            // 只有一台 VCam 时降级处理（仍能工作，但无混合动画）
            if (inactiveCam == null) inactiveCam = activeCam;

            ConfigureSlot(inactiveCam, inactiveConfiner, area);
            inactiveCam.Priority = _globalActivePriority;
            activeCam.Priority   = 0;
            _activeSlot          = nextIsA ? 0 : 1;
        }

        private static void ConfigureSlot(
            CinemachineCamera vcam, CinemachineConfiner2D confiner, CameraArea area)
        {
            if (confiner != null && area.ConfinerCollider != null)
                confiner.BoundingShape2D = area.ConfinerCollider;
        }

        private void ApplyBlendProfile(CameraBlendProfileSO profile)
        {
            if (_brain != null && profile != null)
                _brain.DefaultBlend = profile.ToBlendDefinition();
        }
    }
}