using UnityEngine;
using UnityEngine.Events;

public class RaftRiverController : MonoBehaviour
{
    [Header("Path")]
    [SerializeField] private Transform[] pathPoints;

    [Header("Steering Input")]
    [SerializeField] private SteeringKeyXR steeringKey;

    [Tooltip("체크하면 키 움직임과 반대로 뗏목이 좌우 이동합니다.")]
    [SerializeField] private bool reverseControl = true;

    [Header("Move Speed")]
    [SerializeField] private float forwardSpeed = 5f;
    [SerializeField] private float turnSpeed = 4f;

    [Header("Side Control")]
    [SerializeField] private float sideMoveSpeed = 16f;
    [SerializeField] private float sideAcceleration = 40f;

    [Tooltip("강 중앙선 기준 좌우 이동 가능 범위입니다. 동굴 폭 46이면 14~16 추천.")]
    [SerializeField] private float maxSideOffset = 16f;

    [Header("Path Follow Feel")]
    [SerializeField] private float pathFollowSmoothTime = 0.28f;
    [Range(0f, 1f)]
    [SerializeField] private float rotationVelocityBlend = 0.45f;
    [SerializeField] private float steeringYawAngle = 18f;

    [Header("Arrival")]
    [SerializeField] private float pointReachDistance = 1.5f;

    [Header("Events")]
    public UnityEvent onArrived;

    private int currentPointIndex = 0;
    private float sideOffset = 0f;
    private float sideVelocity = 0f;
    private float currentSteeringInput = 0f;

    private Vector3 currentCenterPosition;
    private Vector3 currentForward;
    private Vector3 currentRight;
    private Vector3 positionSmoothVelocity;
    private Vector3 previousPosition;

    private bool isFinished = false;
    private bool warnedMissingSteeringKey;

    public bool IsFinished => isFinished;

    private void Awake()
    {
        ResolveSteeringKey();
    }

    private void Start()
    {
        ResolveSteeringKey();

        if (pathPoints == null || pathPoints.Length == 0)
        {
            Debug.LogWarning("[RaftRiverController] Path Points가 비어 있습니다.", this);
            enabled = false;
            return;
        }

        currentCenterPosition = transform.position;
        currentForward = transform.forward;
        currentRight = transform.right;
        previousPosition = transform.position;

        // 첫 목표 지점은 0번이 아니라 1번부터 가는 것이 자연스러울 때가 많음.
        // 단, 0번이 현재 위치와 다르면 그대로 0번부터 이동.
        currentPointIndex = 0;
    }

    private void Update()
    {
        if (isFinished)
            return;

        MoveAlongPath();
        HandleSideControl();
        ApplyRaftPositionAndRotation();
    }

    private void MoveAlongPath()
    {
        SkipMissingPathPoints();

        if (currentPointIndex >= pathPoints.Length)
        {
            FinishRaftRide();
            return;
        }

        Transform targetPoint = pathPoints[currentPointIndex];

        Vector3 toTarget = targetPoint.position - currentCenterPosition;
        toTarget.y = 0f;

        float distance = toTarget.magnitude;

        if (distance < pointReachDistance)
        {
            currentPointIndex++;

            if (currentPointIndex >= pathPoints.Length)
            {
                FinishRaftRide();
                return;
            }

            targetPoint = pathPoints[currentPointIndex];
            toTarget = targetPoint.position - currentCenterPosition;
            toTarget.y = 0f;
        }

        if (toTarget.sqrMagnitude < 0.001f)
            return;

        currentForward = toTarget.normalized;
        currentCenterPosition += currentForward * forwardSpeed * Time.deltaTime;

        // 진행 방향 기준 오른쪽 벡터
        currentRight = Vector3.Cross(Vector3.up, currentForward).normalized;
    }

    private void HandleSideControl()
    {
        float input = 0f;
        ResolveSteeringKey();

        if (steeringKey != null)
        {
            input = steeringKey.SteeringValue;
        }
        else
        {
            input = ReadLegacyHorizontalInput();

            if (!warnedMissingSteeringKey)
            {
                warnedMissingSteeringKey = true;
                Debug.LogWarning("[RaftRiverController] SteeringKeyXR 참조가 없어 좌우 조향 없이 전진합니다.", this);
            }
        }

        // 반전은 여기서만 처리
        if (reverseControl)
        {
            input *= -1f;
        }

        currentSteeringInput = input;

        float targetSideVelocity = input * sideMoveSpeed;
        sideVelocity = Mathf.MoveTowards(
            sideVelocity,
            targetSideVelocity,
            sideAcceleration * Time.deltaTime
        );

        sideOffset += sideVelocity * Time.deltaTime;
        sideOffset = Mathf.Clamp(sideOffset, -maxSideOffset, maxSideOffset);

        if (Mathf.Approximately(Mathf.Abs(sideOffset), maxSideOffset) &&
            Mathf.Sign(sideVelocity) == Mathf.Sign(sideOffset))
        {
            sideVelocity = 0f;
        }
    }

    private void ApplyRaftPositionAndRotation()
    {
        previousPosition = transform.position;

        Vector3 targetPosition = currentCenterPosition + currentRight * sideOffset;

        // 현재 뗏목 높이 유지
        targetPosition.y = transform.position.y;

        float smoothTime = Mathf.Max(0.01f, pathFollowSmoothTime);
        transform.position = Vector3.SmoothDamp(
            transform.position,
            targetPosition,
            ref positionSmoothVelocity,
            smoothTime
        );

        if (currentForward != Vector3.zero)
        {
            Vector3 frameVelocity = transform.position - previousPosition;
            frameVelocity.y = 0f;

            Vector3 lookDirection = currentForward;
            if (frameVelocity.sqrMagnitude > 0.0001f)
            {
                lookDirection = Vector3.Slerp(
                    currentForward,
                    frameVelocity.normalized,
                    rotationVelocityBlend
                );
            }

            Quaternion targetRotation =
                Quaternion.LookRotation(lookDirection, Vector3.up) *
                Quaternion.Euler(0f, currentSteeringInput * steeringYawAngle, 0f);

            transform.rotation = Quaternion.Slerp(
                transform.rotation,
                targetRotation,
                turnSpeed * Time.deltaTime
            );
        }
    }

    private void FinishRaftRide()
    {
        if (isFinished)
            return;

        isFinished = true;

        Debug.Log("[RaftRiverController] 목적지 도착. 뗏목 정지.");

        onArrived?.Invoke();
    }

    public void StopRaft()
    {
        isFinished = true;
    }

    public void ResumeRaft()
    {
        isFinished = false;
    }

    public void SetSteeringKey(SteeringKeyXR newSteeringKey)
    {
        steeringKey = newSteeringKey;
        warnedMissingSteeringKey = false;
    }

    private void ResolveSteeringKey()
    {
        if (steeringKey != null)
            return;

        steeringKey = GetComponentInChildren<SteeringKeyXR>(true);
    }

    private void SkipMissingPathPoints()
    {
        while (currentPointIndex < pathPoints.Length && pathPoints[currentPointIndex] == null)
        {
            currentPointIndex++;
        }
    }

    private float ReadLegacyHorizontalInput()
    {
#if ENABLE_LEGACY_INPUT_MANAGER
        return Input.GetAxis("Horizontal");
#else
        return 0f;
#endif
    }
}