using UnityEngine;
using Unity.Cinemachine;

/// <summary>
/// Drives the screen-space radial "hero cutout". Every late frame it projects the local player to
/// screen space and feeds that position + a circle radius/feather + the player's eye-space depth into
/// two global shader properties (<c>_HeroCutoutPosRadius</c>, <c>_HeroCutoutDepthOn</c>) that the
/// <c>Custom/HeroCutoutLit</c> shader reads to clip occluder geometry between the camera and the
/// player - punching a soft see-through hole toward the character.
///
/// The effect is only armed while the third-person orbit <see cref="CinemachineCamera"/> is the live
/// Cinemachine camera (i.e. Player Control / Paint mode). In first-person, free-cam, or while a menu
/// is open a different vcam is live, so the cutout disarms and occluders render solid. Disarming sets
/// the global "enabled" flag to 0, which also matches the zero-initialised default - so any scene
/// without this driver leaves cutout materials looking exactly like URP/Lit.
///
/// 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;

    [Header("Circle")]
    [Tooltip("Radius of the see-through circle, as a fraction of screen height (0.13 = 13% of height).")]
    [Range(0.02f, 0.6f)] public float radius = 0.13f;

    [Tooltip("Soft-edge width of the circle, as a fraction of screen height.")]
    [Range(0f, 0.3f)] public float feather = 0.05f;

    [Tooltip("Metres added to the player's depth so geometry right at the player isn't clipped away.")]
    public float depthBias = 0.5f;

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

    static readonly int PosRadiusId = Shader.PropertyToID("_HeroCutoutPosRadius");
    static readonly int DepthOnId = Shader.PropertyToID("_HeroCutoutDepthOn");

    private CinemachineCamera _orbitCam;
    private CinemachineBrain _brain;

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

    private void OnDisable() => Disarm();

    private void LateUpdate()
    {
        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 vp = cam.WorldToViewportPoint(heroPos);
        if (vp.z <= 0f) { Disarm(); return; } // hero is behind the camera

        Shader.SetGlobalVector(PosRadiusId, new Vector4(vp.x, vp.y, radius, Mathf.Max(feather, 1e-4f)));
        Shader.SetGlobalVector(DepthOnId, new Vector4(vp.z + depthBias, 1f, 0f, 0f));
    }

    /// <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(DepthOnId, Vector4.zero);
}