using UnityEngine;
using Unity.Cinemachine;

/// <summary>
/// Drives the world-space "hero cutout": occluder geometry that sits inside a cone running from the
/// third-person camera (apex) to the player is clipped away, punching a clean see-through funnel toward
/// the character. Every late frame this feeds two global shader properties (<c>_HeroCutoutTarget</c>,
/// <c>_HeroCutoutParams</c>) that the <c>Custom/HeroCutoutLit</c> shader reads.
///
/// Arming is deliberately simple: a single ray is cast FROM the camera TOWARD the player. If it hits
/// world geometry before reaching the player, the cut is armed; with a clear line of sight the
/// occluders stay solid. There is no multi-sample / silhouette estimation - one ray, one answer.
///
/// The cut volume is defined entirely in the shader as a cone along the camera->player axis: everything
/// BETWEEN camera and player (within the cone) is cut; geometry well behind the player stays solid - so a
/// wall the player stands in front of renders completely normally. The far end fades out across a soft
/// depth band (<see cref="depthFeather"/>) straddling the player rather than snapping off at a hard
/// plane, so an occluder running past the player fades just behind them with no hard cut line. The cone's
/// radius grows with distance from the camera, so the hole keeps a constant on-screen size regardless of
/// occluder depth.
///
/// The effect is only active while the third-person orbit <see cref="CinemachineCamera"/> is the live
/// Cinemachine camera (Player Control / Paint mode). In first-person, free-cam or while a menu is open
/// a different vcam is live and the cutout disarms. Disarming clears the global "enabled" flag (also
/// the zero-initialised default), so any scene without this driver - or any frame with a clear view -
/// leaves cutout materials looking exactly like URP/Lit.
///
/// This replaces the camera pulling in toward the player (Cinemachine Deoccluder): instead of closing
/// the distance to dodge an obstacle, the camera holds its orbit distance and the obstacle is punched
/// see-through.
///
/// Attach to a persistent scene object (e.g. the GameModeManager host).
/// </summary>
[DisallowMultipleComponent]
public class HeroCutout : MonoBehaviour
{
    [Tooltip("Orbit camera input whose CinemachineCamera must be live for the cutout to arm. Empty = found automatically.")]
    public ThirdPersonOrbitInput orbitInput;

    [Tooltip("Game mode manager, used as a fallback source for the live player. Empty = found automatically.")]
    public GameModeManager modes;

    [Tooltip("Switch off the orbit camera's Cinemachine Deoccluder obstacle avoidance at runtime so the " +
             "camera holds its orbit distance and this cutout handles occlusion - instead of the camera " +
             "pulling in toward the player. The scene's Deoccluder asset is left untouched; only its live " +
             "pull-in is disabled (and restored if this driver is disabled).")]
    public bool replaceDeoccluderPullIn = true;

    [Header("Cutout cone")]
    [Tooltip("Radius of the see-through cone AT THE PLAYER, in metres. The cone tapers to nothing at the " +
             "camera, so the hole keeps a constant on-screen size at every occluder depth.")]
    [Range(0.05f, 3f)] public float radius = 0.5f;

    [Tooltip("Soft-edge width of the cone wall at the player, in metres (also tapers toward the camera).")]
    [Range(0f, 1f)] public float feather = 0.15f;

    [Tooltip("Soft depth band (m) straddling the player: instead of stopping at a hard plane at the " +
             "player's depth, the cut fades out across +/- this distance around the player, so an occluder " +
             "running past the player (a shelf board) fades just behind them too instead of showing a hard " +
             "straight cut line. Geometry beyond this band stays fully solid.")]
    [Range(0.01f, 2f)] public float depthFeather = 0.5f;

    [Tooltip("Vertical offset (m) from the follow target the cone aims at (chest/head height).")]
    public float heightOffset = 0f;

    [Header("Occlusion ray (camera -> player)")]
    [Tooltip("Layers that count as occluders. Leave empty (Nothing) to fall back to all default raycast layers.")]
    public LayerMask occluderMask = ~0;

    [Tooltip("Collider tag ignored by the ray (the player's own colliders). Must be an existing tag; " +
             "empty = ignore nothing.")]
    public string ignoreTag = "Player";

    [Tooltip("Metres the ray stops short of the player. Keep at 0 so a wall the player stands right " +
             "behind still arms the cut (everything between camera and player counts). The ray already " +
             "ends AT the player, so geometry behind them is never hit regardless. Raise this only if a " +
             "low camera grazes the floor at the player's feet (better fixed via Height Offset).")]
    [Range(0f, 1.5f)] public float minDistanceFromTarget = 0f;

    [Tooltip("Seconds the cutout stays armed after the view clears again, to stop flicker at occluder edges.")]
    public float occlusionHold = 0.1f;

    static readonly int TargetId = Shader.PropertyToID("_HeroCutoutTarget");
    static readonly int ParamsId = Shader.PropertyToID("_HeroCutoutParams");

    private CinemachineCamera _orbitCam;
    private CinemachineBrain _brain;
    private CinemachineDeoccluder _deoccluder;
    private bool _deoccluderResolved;
    private bool _deoccluderOriginalAvoid;
    private bool _pullInSuppressed;
    private float _lastOccludedTime = -999f;

    private void Awake()
    {
        if (!orbitInput) orbitInput = FindFirstObjectByType<ThirdPersonOrbitInput>(FindObjectsInactive.Include);
        if (!modes) modes = FindFirstObjectByType<GameModeManager>();
        EnsureRefs();

        // CompareTag throws on an undefined tag - validate once so the per-frame ray never does.
        if (!string.IsNullOrEmpty(ignoreTag))
        {
            try { _ = gameObject.CompareTag(ignoreTag); }
            catch
            {
                Debug.LogWarning($"[HeroCutout] Ignore Tag '{ignoreTag}' is not defined; the ray will ignore nothing.", this);
                ignoreTag = string.Empty;
            }
        }
    }

    private void OnDisable()
    {
        Disarm();
        RestoreDeoccluderPullIn();
    }

    private void LateUpdate()
    {
        EnsureRefs();
        ApplyPullInSuppression();

        Camera cam = Camera.main;
        if (!cam) { Disarm(); return; }

        if (!_brain || _brain.gameObject != cam.gameObject)
            _brain = cam.GetComponent<CinemachineBrain>();

        if (!IsThirdPersonLive()) { Disarm(); return; }

        Transform target = ResolveHeroTarget();
        if (!target) { Disarm(); return; }

        Vector3 heroPos = target.position + Vector3.up * heightOffset;
        Vector3 camPos = cam.transform.position;

        // Only punch the tube when something actually stands between the player and the camera; with a
        // clear view the occluders stay solid. A short hold after the last blocked frame avoids flicker
        // when the single ray grazes an occluder edge.
        if (IsViewBlocked(camPos, heroPos)) _lastOccludedTime = Time.time;
        if (Time.time - _lastOccludedTime > Mathf.Max(0f, occlusionHold)) { Disarm(); return; }

        // Same hero point feeds the ray and the cone axis, so the gate and the cut volume agree.
        Shader.SetGlobalVector(TargetId, new Vector4(heroPos.x, heroPos.y, heroPos.z, 1f));
        Shader.SetGlobalVector(ParamsId, new Vector4(Mathf.Max(0f, radius), Mathf.Max(1e-4f, feather), Mathf.Max(1e-4f, depthFeather), 0f));
    }

    /// <summary>
    /// Single ray, camera -> player. Returns true when a non-ignored collider blocks the view before
    /// the ray reaches the player (stopped short by <see cref="minDistanceFromTarget"/> so the wall the
    /// player stands against / the floor at their feet never counts). Anything "between" the camera and
    /// the player is necessarily the first thing the ray hits, so checking the first hit is enough.
    /// </summary>
    private bool IsViewBlocked(Vector3 camPos, Vector3 heroPos)
    {
        Vector3 delta = heroPos - camPos;
        float dist = delta.magnitude;
        if (dist <= 1e-3f) return false;
        Vector3 dir = delta / dist;

        float maxDist = dist - Mathf.Clamp(minDistanceFromTarget, 0f, dist);
        if (maxDist <= 1e-3f) return false;

        int mask = occluderMask.value != 0 ? occluderMask.value : Physics.DefaultRaycastLayers;

        if (!Physics.Raycast(camPos, dir, out RaycastHit hit, maxDist, mask, QueryTriggerInteraction.Ignore))
            return false;

        // First (closest) hit decides: if it's the ignored player, nothing real is in between.
        return string.IsNullOrEmpty(ignoreTag) || !hit.collider.CompareTag(ignoreTag);
    }

    /// <summary>True only when the orbit vcam is the live Cinemachine camera (third-person modes).</summary>
    private bool IsThirdPersonLive()
    {
        if (!_orbitCam || !_brain) return false;
        var live = _brain.ActiveVirtualCamera as CinemachineCamera;
        return live && live == _orbitCam;
    }

    private Transform ResolveHeroTarget()
    {
        if (_orbitCam && _orbitCam.Follow) return _orbitCam.Follow;
        if (modes && modes.Player) return modes.Player.transform;
        return null;
    }

    /// <summary>Clears the "enabled" flag so cutout materials render as plain URP/Lit.</summary>
    private void Disarm() => Shader.SetGlobalVector(TargetId, Vector4.zero);

    /// <summary>
    /// Lazily resolves the orbit vcam and its Cinemachine Deoccluder (they may live in a scene that
    /// loads after this driver). Captures the deoccluder's authored obstacle-avoidance state once so it
    /// can be restored later.
    /// </summary>
    private void EnsureRefs()
    {
        if (!_orbitCam && orbitInput) _orbitCam = orbitInput.GetComponent<CinemachineCamera>();
        if (!_deoccluderResolved && _orbitCam)
        {
            _deoccluder = _orbitCam.GetComponent<CinemachineDeoccluder>();
            if (_deoccluder) _deoccluderOriginalAvoid = _deoccluder.AvoidObstacles.Enabled;
            _deoccluderResolved = true;
        }
    }

    /// <summary>
    /// Switches the deoccluder's obstacle avoidance (the camera pull-in) off while this driver replaces
    /// it with the cutout, or restores the authored state when the replacement is turned off. Only
    /// toggles on transitions, so it never fights a value changed elsewhere mid-frame.
    /// </summary>
    private void ApplyPullInSuppression()
    {
        if (!_deoccluder) return;

        if (replaceDeoccluderPullIn && !_pullInSuppressed)
        {
            _deoccluder.AvoidObstacles.Enabled = false;
            _pullInSuppressed = true;
        }
        else if (!replaceDeoccluderPullIn && _pullInSuppressed)
        {
            _deoccluder.AvoidObstacles.Enabled = _deoccluderOriginalAvoid;
            _pullInSuppressed = false;
        }
    }

    /// <summary>Restores the deoccluder's authored pull-in if this driver had suppressed it.</summary>
    private void RestoreDeoccluderPullIn()
    {
        if (_pullInSuppressed && _deoccluder)
        {
            _deoccluder.AvoidObstacles.Enabled = _deoccluderOriginalAvoid;
            _pullInSuppressed = false;
        }
    }
}