using UnityEngine;
#if ENABLE_INPUT_SYSTEM
using UnityEngine.InputSystem;
#endif

/// <summary>
/// CharacterController-based player: camera-relative WASD movement, manual gravity
/// and jumping, sliding off too-steep slopes/edges, and a wall-climb mode.
///
/// Wall-climb (entered on wall/ceiling contact) uses wall-relative controls: W
/// moves toward the wall and climbs up once against it, S backs off and detaches,
/// A/D strafe along the wall. Gravity and jumping are disabled while climbing;
/// reaching the top edge mantles the character over onto the surface.
///
/// Named PlayerCharacterController to avoid a clash with Unity.VisualScripting's
/// example "PlayerController".
/// </summary>
[RequireComponent(typeof(CharacterController))]
[DisallowMultipleComponent]
public class PlayerCharacterController : MonoBehaviour
{
    [Header("Movement")]
    [Tooltip("Horizontal movement speed (units/second).")]
    public float moveSpeed = 4f;

    [Tooltip("Interpret WASD relative to the camera (off = world X/Z axes).")]
    public bool cameraRelative = true;

    [Tooltip("Camera used for camera-relative movement. Empty = Camera.main.")]
    public Transform cameraTransform;

    [Header("Rotation")]
    [Tooltip("Smoothly turn the character to face its movement direction.")]
    public bool rotateTowardMovement = true;

    [Tooltip("Turn speed in degrees per second.")]
    public float rotationSpeed = 720f;

    [Header("Jump & Gravity")]
    [Tooltip("Peak jump height in units.")]
    public float jumpHeight = 1.2f;

    [Tooltip("Gravity in units per second squared (negative = downward).")]
    public float gravity = -19.62f;

    [Tooltip("Small downward velocity kept while grounded for reliable ground contact.")]
    public float groundedStickVelocity = -2f;

    [Header("Slope Sliding")]
    [Tooltip("Slide down surfaces steeper than the CharacterController's Slope Limit instead of balancing on them.")]
    public bool slideDownSteepSlopes = true;

    [Tooltip("How quickly the slide accelerates (units/second squared).")]
    public float slideAcceleration = 20f;

    [Tooltip("Maximum downhill slide speed (units/second).")]
    public float maxSlideSpeed = 8f;

    [Tooltip("Steering control kept while sliding (0 = none, 1 = full).")]
    [Range(0f, 1f)]
    public float slideControl = 0.3f;

    [Header("Wall Climb")]
    [Tooltip("Enter wall-climb mode on wall/ceiling contact: stick to the surface, move at reduced speed, ignore gravity and jumping.")]
    public bool enableWallClimb = true;

    [Tooltip("Minimum surface angle from 'up' (degrees) that counts as a climbable wall/ceiling rather than a slope.")]
    [Range(50f, 180f)]
    public float wallMinAngle = 80f;

    [Tooltip("Speed multiplier for climbing up and strafing while wall-climbing (0.5 = half speed).")]
    [Range(0f, 1f)]
    public float wallClimbSpeedMultiplier = 0.5f;

    [Tooltip("Slow speed for moving toward (W) or away from (S) the wall while climbing.")]
    public float wallApproachSpeed = 0.5f;

    [Tooltip("Gap below which the character counts as fully against the wall (W then climbs up).")]
    public float wallContactDistance = 0.05f;

    [Tooltip("Gap from the wall at which holding back (S) leaves wall-climb mode.")]
    public float wallDetachDistance = 0.25f;

    [Tooltip("Grace period (seconds) of lost contact tolerated before leaving wall-climb mode.")]
    public float wallExitGrace = 0.15f;

    /// <summary>
    /// When false, movement/jump input is ignored but gravity and ground contact
    /// keep running. Toggled by the GameModeManager.
    /// </summary>
    public bool ControlEnabled { get; set; } = true;

    /// <summary>True while in wall-climb mode.</summary>
    public bool IsWallClimbing => _isWallClimbing;

    private CharacterController _controller;
    private float _verticalVelocity;

    // Ground contact normal from the latest Move (for slope sliding).
    private Vector3 _groundNormal = Vector3.up;
    private bool _groundNormalUpdated;
    private float _slideSpeed;

    // Wall-climb state.
    private bool _isWallClimbing;
    private Vector3 _wallNormal;
    private Vector3 _wallNormalAccum;     // summed wall normals during the latest Move
    private bool _wallContactThisFrame;
    private float _lostContactTimer;
    private readonly RaycastHit[] _wallProbe = new RaycastHit[8];

    // Mantle (top-out) state.
    private bool _mantling;
    private bool _mantleClearedFeet;      // phase 1 done: capsule fully above the edge
    private float _mantleOverDist;        // phase 2 forward distance over the top
    private float _mantleTimer;           // safety cap
    private float _reentryCooldown;       // blocks re-grabbing right after topping out

    void Awake()
    {
        _controller = GetComponent<CharacterController>();
        if (!cameraTransform && Camera.main)
            cameraTransform = Camera.main.transform;
    }

    void Update()
    {
        float h = 0f, v = 0f;
        bool jumpPressed = false;

        // Skip input when control is disabled (e.g. paint mode); gravity and
        // grounding below still run so the player stays planted.
        if (ControlEnabled)
        {
#if ENABLE_INPUT_SYSTEM
            var keyboard = Keyboard.current;
            if (keyboard != null)
            {
                if (keyboard.aKey.isPressed) h -= 1f;
                if (keyboard.dKey.isPressed) h += 1f;
                if (keyboard.sKey.isPressed) v -= 1f;
                if (keyboard.wKey.isPressed) v += 1f;
                jumpPressed = keyboard.spaceKey.wasPressedThisFrame;
            }
#else
            h = Input.GetAxisRaw("Horizontal");
            v = Input.GetAxisRaw("Vertical");
            jumpPressed = Input.GetButtonDown("Jump");
#endif
        }

        Vector3 inputDir = new Vector3(h, 0f, v);
        if (inputDir.sqrMagnitude > 1f)
            inputDir.Normalize();

        Vector3 moveDir;
        if (cameraRelative && cameraTransform)
        {
            // Project the camera axes onto the ground plane so movement stays horizontal.
            Vector3 forward = cameraTransform.forward;
            forward.y = 0f;
            forward.Normalize();
            Vector3 right = cameraTransform.right;
            right.y = 0f;
            right.Normalize();
            moveDir = forward * inputDir.z + right * inputDir.x;
        }
        else
        {
            moveDir = inputDir;
        }

        UpdateWallClimbState();

        // Latch the wall normal for this frame, then reset the per-frame contact
        // accumulators (OnControllerColliderHit refills them during Move).
        if (_wallContactThisFrame && _wallNormalAccum.sqrMagnitude > 1e-6f)
            _wallNormal = _wallNormalAccum.normalized;
        _wallContactThisFrame = false;
        _wallNormalAccum = Vector3.zero;

        if (_isWallClimbing)
        {
            ApplyWallClimbMovement(h, v, Time.deltaTime);
            return;
        }

        // A ground normal steeper than the slope limit is too steep to stand on
        // (also covers balancing on a sharp box edge).
        float slopeAngle = Vector3.Angle(_groundNormal, Vector3.up);
        bool onSteepSlope = slideDownSteepSlopes
            && _controller.isGrounded
            && slopeAngle > _controller.slopeLimit + 0.01f;

        if (_controller.isGrounded)
        {
            if (_verticalVelocity < 0f)
                _verticalVelocity = groundedStickVelocity;

            // No jumping off a slope too steep to stand on.
            if (jumpPressed && !onSteepSlope)
                _verticalVelocity = Mathf.Sqrt(jumpHeight * -2f * gravity);
        }

        _verticalVelocity += gravity * Time.deltaTime;

        Vector3 slideVelocity = Vector3.zero;
        if (onSteepSlope)
        {
            Vector3 slideDir = Vector3.ProjectOnPlane(Vector3.down, _groundNormal).normalized;
            _slideSpeed = Mathf.Min(_slideSpeed + slideAcceleration * Time.deltaTime, maxSlideSpeed);
            slideVelocity = slideDir * _slideSpeed;
            moveDir *= slideControl; // reduced steering while sliding
        }
        else
        {
            _slideSpeed = 0f;
        }

        Vector3 velocity = moveDir * moveSpeed + slideVelocity + Vector3.up * _verticalVelocity;

        // Move fires OnControllerColliderHit, which refills the ground normal;
        // fall back to "up" if nothing was hit.
        _groundNormalUpdated = false;
        _controller.Move(velocity * Time.deltaTime);
        if (!_groundNormalUpdated)
            _groundNormal = Vector3.up;

        if (rotateTowardMovement && moveDir.sqrMagnitude > 0.0001f)
        {
            Quaternion target = Quaternion.LookRotation(moveDir, Vector3.up);
            transform.rotation = Quaternion.RotateTowards(
                transform.rotation, target, rotationSpeed * Time.deltaTime);
        }
    }

    /// <summary>
    /// Enters wall-climb mode on any wall/ceiling contact. Leaving while climbing
    /// is handled in <see cref="ApplyWallClimbMovement"/>.
    /// </summary>
    private void UpdateWallClimbState()
    {
        if (_reentryCooldown > 0f)
            _reentryCooldown -= Time.deltaTime;

        if (!enableWallClimb || !ControlEnabled)
        {
            if (_isWallClimbing)
                ExitWallClimb();
            return;
        }

        // The cooldown prevents instantly re-grabbing the edge we just mantled over.
        if (!_isWallClimbing && _wallContactThisFrame && _reentryCooldown <= 0f)
        {
            _isWallClimbing = true;
            _lostContactTimer = 0f;
            _verticalVelocity = 0f;
            _slideSpeed = 0f;
        }
    }

    /// <summary>
    /// Wall-relative movement while climbing: W approaches the wall then climbs up,
    /// S backs off and detaches, A/D strafe along the wall. The wall normal and gap
    /// are measured each frame by a raycast. No gravity, jump or forced alignment.
    /// </summary>
    private void ApplyWallClimbMovement(float h, float v, float dt)
    {
        if (_mantling)
        {
            MantleOverEdge(dt);
            return;
        }

        bool found = ProbeWall(out Vector3 probedNormal, out float gap);
        if (found)
        {
            _wallNormal = probedNormal;
            _lostContactTimer = 0f;
        }
        else
        {
            // The center ray lost the wall. If we are climbing up (W) and the wall
            // still exists at foot level, we reached the top edge -> mantle over.
            if (v > 0f && WallInFront(_controller.height * 0.5f))
            {
                _mantling = true;
                _mantleClearedFeet = false;
                _mantleOverDist = 0f;
                _mantleTimer = 0f;
                MantleOverEdge(dt);
                return;
            }

            // Wall genuinely gone: leave after the grace period.
            _lostContactTimer += dt;
            gap = wallDetachDistance + 1f; // treat as "far" so it cannot block exit
            if (_lostContactTimer >= wallExitGrace)
            {
                ExitWallClimb();
                return;
            }
        }

        // Basis on the wall plane: "up along the wall" and "right".
        Vector3 climbUp = Vector3.ProjectOnPlane(Vector3.up, _wallNormal);
        if (climbUp.sqrMagnitude < 1e-6f) // degenerate on a flat ceiling
            climbUp = Vector3.ProjectOnPlane(transform.forward, _wallNormal);
        climbUp.Normalize();
        Vector3 right = Vector3.Cross(_wallNormal, climbUp).normalized;

        float climbSpeed = moveSpeed * wallClimbSpeedMultiplier;

        Vector3 velocity = right * (h * climbSpeed); // A/D strafe

        bool detach = false;
        if (v > 0f)
        {
            // W: approach the wall while there is a gap, otherwise climb up.
            if (gap > wallContactDistance)
                velocity += -_wallNormal * (v * wallApproachSpeed);
            else
                velocity += climbUp * (v * climbSpeed);
        }
        else if (v < 0f)
        {
            // S: back away (v < 0 => away from wall); detach once far enough.
            velocity += -_wallNormal * (v * wallApproachSpeed);
            if (gap >= wallDetachDistance)
                detach = true;
        }

        _controller.Move(velocity * dt);

        if (detach)
            ExitWallClimb();
    }

    /// <summary>
    /// Raycasts from the character center toward the wall to find the current
    /// normal and the gap to it. Our own colliders are skipped. False = no wall.
    /// </summary>
    private bool ProbeWall(out Vector3 normal, out float gap)
    {
        normal = _wallNormal;
        gap = 0f;

        Vector3 origin = transform.position + _controller.center;
        float radius = _controller.radius;
        float maxDist = radius + wallDetachDistance + 0.5f;

        int count = Physics.RaycastNonAlloc(
            origin, -_wallNormal, _wallProbe, maxDist, ~0, QueryTriggerInteraction.Ignore);

        float best = float.MaxValue;
        bool found = false;
        for (int i = 0; i < count; i++)
        {
            if (_wallProbe[i].collider.transform.IsChildOf(transform)) // skip our own colliders
                continue;
            if (_wallProbe[i].distance < best)
            {
                best = _wallProbe[i].distance;
                normal = _wallProbe[i].normal;
                found = true;
            }
        }

        if (found)
            gap = Mathf.Max(0f, best - radius);
        return found;
    }

    /// <summary>
    /// Pulls the character up and over the wall's top edge: phase 1 rises until the
    /// capsule clears the edge, phase 2 moves forward onto the surface, then exits.
    /// A short re-grab cooldown stops the passed edge from re-triggering a climb.
    /// </summary>
    private void MantleOverEdge(float dt)
    {
        _mantleTimer += dt;
        float speed = moveSpeed * wallClimbSpeedMultiplier;

        Vector3 forward = -_wallNormal;
        forward.y = 0f;
        forward = forward.sqrMagnitude > 1e-6f ? forward.normalized : transform.forward;

        if (!_mantleClearedFeet)
        {
            // Phase 1: climb straight up until no wall is left in front of the feet.
            _controller.Move(Vector3.up * (speed * dt));
            if (!WallInFront(_controller.height * 0.5f))
                _mantleClearedFeet = true;
        }
        else
        {
            // Phase 2: move forward onto the top surface, then finish.
            _controller.Move(forward * (speed * dt));
            _mantleOverDist += speed * dt;
            if (_mantleOverDist >= _controller.radius * 2f + 0.15f || _controller.isGrounded)
            {
                _reentryCooldown = 0.3f;
                ExitWallClimb();
                return;
            }
        }

        // Safety: never mantle indefinitely (e.g. blocked by other geometry).
        if (_mantleTimer >= 2f)
        {
            _reentryCooldown = 0.3f;
            ExitWallClimb();
        }
    }

    /// <summary>
    /// Horizontal ray toward the wall from a point below the center. Distinguishes a
    /// top edge (wall still present lower down) from the wall being truly gone.
    /// </summary>
    private bool WallInFront(float downOffset)
    {
        Vector3 origin = transform.position + _controller.center - Vector3.up * downOffset;
        float maxDist = _controller.radius + wallDetachDistance + 0.5f;

        int count = Physics.RaycastNonAlloc(
            origin, -_wallNormal, _wallProbe, maxDist, ~0, QueryTriggerInteraction.Ignore);
        for (int i = 0; i < count; i++)
        {
            if (_wallProbe[i].collider.transform.IsChildOf(transform))
                continue;
            return true;
        }
        return false;
    }

    /// <summary>Leaves wall-climb mode and resets vertical velocity so the player falls cleanly.</summary>
    private void ExitWallClimb()
    {
        _isWallClimbing = false;
        _lostContactTimer = 0f;
        _verticalVelocity = 0f;
        _mantling = false;
        _mantleClearedFeet = false;
        _mantleOverDist = 0f;
        _mantleTimer = 0f;
    }

    /// <summary>
    /// Collects contact normals during Move: wall/ceiling contacts feed the
    /// wall-climb detector, the flattest upward contact becomes the ground normal.
    /// </summary>
    private void OnControllerColliderHit(ControllerColliderHit hit)
    {
        if (enableWallClimb)
        {
            float angle = Vector3.Angle(hit.normal, Vector3.up);
            if (angle >= wallMinAngle)
            {
                _wallContactThisFrame = true;
                _wallNormalAccum += hit.normal;
            }
        }

        // Ignore near-vertical walls and ceilings for ground-normal collection.
        if (hit.normal.y <= 0.05f)
            return;

        // Keep the flattest (most supportive) contact seen this frame.
        if (!_groundNormalUpdated || hit.normal.y > _groundNormal.y)
        {
            _groundNormal = hit.normal;
            _groundNormalUpdated = true;
        }
    }
}