using Cinemachine;
using UnityEngine;

namespace SepCore.CameraModule
{
    /// <summary>
    /// 基于 Cinemachine 的相机控制器。挂载到场景中的主相机上（主相机需有 CinemachineBrain）。
    /// 会在主相机同级自动创建 CinemachineVirtualCamera，避免虚拟相机成为被 Brain 驱动相机的子物体。
    /// </summary>
    [RequireComponent(typeof(CinemachineBrain))]
    public class CinemachineCameraController : MonoBehaviour, ICameraController
    {
        [SerializeField] private CameraEffectSettings _settings = CameraEffectSettings.Default;
        [SerializeField] private Vector3 _baseFollowOffset = new Vector3(0f, 10f, -10f);
        [SerializeField] private bool _lockRotation = true;
        [SerializeField] private Vector3 _fixedRotationEuler = new Vector3(90f, 0f, 0f);

        private CinemachineVirtualCamera _virtualCamera;
        private CinemachineTransposer _transposer;
        private bool _followDampingEnabled = true;
        private bool _movementDirectionOffsetEnabled = true;

        private Vector3 _currentAppliedOffset;
        private Vector3 _previousTargetPosition;
        private bool _hasTarget;

        public Transform Target { get; private set; }
        public CameraEffectSettings CurrentSettings => _settings;

        private void Awake()
        {
            CreateVirtualCamera();
        }

        private void OnValidate()
        {
            ApplyRotationMode();
        }

        private void LateUpdate()
        {
            if (!_hasTarget || Target == null)
                return;

            if (_movementDirectionOffsetEnabled)
                UpdateMovementDirectionOffset();
            else
                ResetOffsetSmoothly();

            _previousTargetPosition = Target.position;

            if (_lockRotation)
                ApplyFixedRotation();
        }

        public void SetTarget(Transform target)
        {
            Target = target;
            _hasTarget = target != null;

            if (_virtualCamera == null)
                return;

            _virtualCamera.Follow = target;
            ApplyRotationMode();

            if (_hasTarget)
            {
                _previousTargetPosition = target.position;
                _currentAppliedOffset = _baseFollowOffset;
                _transposer.m_FollowOffset = _baseFollowOffset;
            }
        }

        public void EnableEffect(CameraEffectType effect)
        {
            switch (effect)
            {
                case CameraEffectType.FollowDamping:
                    _followDampingEnabled = true;
                    ApplyDampingValues();
                    break;
                case CameraEffectType.MovementDirectionOffset:
                    _movementDirectionOffsetEnabled = true;
                    break;
            }
        }

        public void DisableEffect(CameraEffectType effect)
        {
            switch (effect)
            {
                case CameraEffectType.FollowDamping:
                    _followDampingEnabled = false;
                    ApplyDampingValues();
                    break;
                case CameraEffectType.MovementDirectionOffset:
                    _movementDirectionOffsetEnabled = false;
                    break;
            }
        }

        public bool IsEffectEnabled(CameraEffectType effect)
        {
            return effect switch
            {
                CameraEffectType.FollowDamping => _followDampingEnabled,
                CameraEffectType.MovementDirectionOffset => _movementDirectionOffsetEnabled,
                _ => false,
            };
        }

        public void ApplySettings(CameraEffectSettings settings)
        {
            _settings = settings;
            ApplyDampingValues();
        }

        private void CreateVirtualCamera()
        {
            var go = new GameObject("CM_CameraController_VCam");
            go.transform.SetParent(transform.parent, false);
            go.transform.rotation = Quaternion.Euler(_fixedRotationEuler);
            _virtualCamera = go.AddComponent<CinemachineVirtualCamera>();

            _virtualCamera.m_Lens.FieldOfView = 60f;

            _transposer = _virtualCamera.AddCinemachineComponent<CinemachineTransposer>();
            _transposer.m_BindingMode = CinemachineTransposer.BindingMode.WorldSpace;
            _transposer.m_FollowOffset = _baseFollowOffset;

            ApplyRotationMode();

            ApplyDampingValues();
        }

        private void ApplyRotationMode()
        {
            if (_virtualCamera == null)
                return;

            if (_lockRotation)
            {
                _virtualCamera.LookAt = null;
                _virtualCamera.DestroyCinemachineComponent<CinemachineHardLookAt>();
                ApplyFixedRotation();
                return;
            }

            _virtualCamera.LookAt = Target;

            if (_virtualCamera.GetCinemachineComponent<CinemachineHardLookAt>() == null)
                _virtualCamera.AddCinemachineComponent<CinemachineHardLookAt>();
        }

        private void ApplyFixedRotation()
        {
            if (_virtualCamera == null)
                return;

            _virtualCamera.transform.rotation = Quaternion.Euler(_fixedRotationEuler);
        }

        private void ApplyDampingValues()
        {
            if (_transposer == null)
                return;

            if (_followDampingEnabled)
            {
                _transposer.m_XDamping = _settings.dampingX;
                _transposer.m_YDamping = _settings.dampingY;
                _transposer.m_ZDamping = _settings.dampingZ;
            }
            else
            {
                _transposer.m_XDamping = 0f;
                _transposer.m_YDamping = 0f;
                _transposer.m_ZDamping = 0f;
            }
        }

        private void UpdateMovementDirectionOffset()
        {
            float dt = Time.deltaTime;
            Vector3 velocity = (Target.position - _previousTargetPosition) / Mathf.Max(dt, 0.0001f);
            float speed = new Vector3(velocity.x, 0f, velocity.z).magnitude;

            Vector3 targetOffset = _baseFollowOffset;

            if (speed > _settings.offsetDeadZone)
            {
                Vector3 dir = new Vector3(velocity.x, 0f, velocity.z).normalized;
                float offsetAmount = Mathf.Min(speed * _settings.offsetStrength, _settings.maxOffsetDistance);
                targetOffset += dir * offsetAmount;
            }

            _currentAppliedOffset = Vector3.Lerp(
                _currentAppliedOffset,
                targetOffset,
                _settings.offsetSmoothing * dt
            );

            _transposer.m_FollowOffset = _currentAppliedOffset;
        }

        private void ResetOffsetSmoothly()
        {
            _currentAppliedOffset = Vector3.Lerp(
                _currentAppliedOffset,
                _baseFollowOffset,
                _settings.offsetSmoothing * Time.deltaTime
            );
            _transposer.m_FollowOffset = _currentAppliedOffset;
        }
    }
}