using UnityEngine;

public partial class MeshPainter
{
    // --- Setup (shared) ---

    private void SetupCollider()
    {
        _collider = GetComponent<MeshCollider>();
        if (!_collider) _collider = gameObject.AddComponent<MeshCollider>();
        _collider.convex = false; // non-convex provides triangleIndex / textureCoord

        // An always-on SkinnedColliderBaker (skinned rigs only) owns the bake even outside paint
        // mode; we delegate to it and only borrow its mesh. Without one we keep our own legacy bake.
        _baker = _skinned ? GetComponent<SkinnedColliderBaker>() : null;
        if (!_baker) _bakedMesh = new Mesh { name = "MeshPainter_Baked" };
        BakeColliderMesh();
    }

    private void BakeColliderMesh()
    {
        if (_baker)
        {
            // Baker already baked (negative execution order) and keeps _collider.sharedMesh fresh;
            // we only track its mesh for the GPU raster path. No bake here - that's the whole point.
            _bakedMesh = _baker.BakedMesh;
        }
        else if (_skinned)
        {
            // Static skinned mesh: bake into local coordinates (scale = 1).
            _skinned.BakeMesh(_bakedMesh);
            _collider.sharedMesh = null;
            _collider.sharedMesh = _bakedMesh;
        }
        else
        {
            var mf = GetComponent<MeshFilter>();
            if (mf) _collider.sharedMesh = mf.sharedMesh;
        }
    }

    // BuildMeshCaches scratch: refilled per bake without allocating (with updateColliderEveryFrame this
    // runs per frame while painting; mesh.vertices/.triangles/.uv return fresh arrays per call).
    private readonly System.Collections.Generic.List<Vector3> _vertScratch = new System.Collections.Generic.List<Vector3>();
    private int _meshCacheId; // mesh instance the topology/UV caches were built for (0 = none)

    /// <summary>Reads vertices/triangles/UVs of the collider mesh and computes culling data.
    /// Only the vertices change across re-bakes of the same mesh; topology/UVs are fetched once.</summary>
    private void BuildMeshCaches()
    {
        Mesh m = _collider.sharedMesh;
        if (!m) return;

        m.GetVertices(_vertScratch);
        int vCount = _vertScratch.Count;
        if (_verts == null || _verts.Length != vCount) _verts = new Vector3[vCount];
        _vertScratch.CopyTo(_verts);

        if (_meshCacheId != m.GetInstanceID())
        {
            _meshCacheId = m.GetInstanceID();
            _tris = m.triangles;
            _uvs = m.uv;
            // Fallback to the original mesh UVs if the baked mesh dropped them.
            if ((_uvs == null || _uvs.Length != vCount) && _skinned && _skinned.sharedMesh)
                _uvs = _skinned.sharedMesh.uv;
        }

        if (_uvs == null || _uvs.Length != _verts.Length) return;

        int triCount = _tris.Length / 3;
        if (_triCenter == null || _triCenter.Length != triCount)
        {
            _triCenter = new Vector3[triCount];
            _triRadius = new float[triCount];
        }

        double sumArea3D = 0.0, sumAreaUv = 0.0;

        for (int t = 0; t < triCount; t++)
        {
            int i0 = _tris[t * 3], i1 = _tris[t * 3 + 1], i2 = _tris[t * 3 + 2];
            Vector3 a = _verts[i0], b = _verts[i1], c = _verts[i2];

            Vector3 center = (a + b + c) / 3f;
            _triCenter[t] = center;
            float ra = (a - center).sqrMagnitude;
            float rb = (b - center).sqrMagnitude;
            float rc = (c - center).sqrMagnitude;
            _triRadius[t] = Mathf.Sqrt(Mathf.Max(ra, Mathf.Max(rb, rc)));

            sumArea3D += 0.5 * Vector3.Cross(b - a, c - a).magnitude;
            Vector2 ua = _uvs[i0], ub = _uvs[i1], uc = _uvs[i2];
            sumAreaUv += 0.5 * Mathf.Abs(Cross2D(ub - ua, uc - ua));
        }

        if (sumAreaUv > 1e-9) _avgUvToLocal = (float)System.Math.Sqrt(sumArea3D / sumAreaUv);
    }

    /// <summary>
    /// Rasterizes the mesh UV islands into a per-texel coverage marker - the dilation SOURCE / overwrite
    /// guard (island texels are real content edge padding must never overwrite; the gutter stays
    /// paddable). Derived from the STATIC UV layout instead of transient per-stroke coverage, so every
    /// seed (fresh start, load, backend switch) marks the same content and the first stroke after a
    /// load/switch no longer bleeds over existing paint. Built once and cached.
    /// </summary>
    private bool[] GetIslandMask()
    {
        int n = textureSize * textureSize;
        if (_islandMask != null && _islandMask.Length == n) return _islandMask;

        var mask = new bool[n];
        if (_tris == null || _uvs == null) { _islandMask = mask; return mask; }

        float ts = textureSize;
        const float eps = -1e-4f; // matches PaintStamp3D: tolerate 1px cracks between triangles
        int triCount = _tris.Length / 3;

        for (int t = 0; t < triCount; t++)
        {
            int i0 = _tris[t * 3], i1 = _tris[t * 3 + 1], i2 = _tris[t * 3 + 2];
            Vector2 uv0 = _uvs[i0], uv1 = _uvs[i1], uv2 = _uvs[i2];

            float p0x = uv0.x * ts, p0y = uv0.y * ts;
            float p1x = uv1.x * ts, p1y = uv1.y * ts;
            float p2x = uv2.x * ts, p2y = uv2.y * ts;

            int minX = Mathf.Clamp(Mathf.FloorToInt(Mathf.Min(p0x, Mathf.Min(p1x, p2x))), 0, textureSize - 1);
            int maxX = Mathf.Clamp(Mathf.CeilToInt(Mathf.Max(p0x, Mathf.Max(p1x, p2x))), 0, textureSize - 1);
            int minY = Mathf.Clamp(Mathf.FloorToInt(Mathf.Min(p0y, Mathf.Min(p1y, p2y))), 0, textureSize - 1);
            int maxY = Mathf.Clamp(Mathf.CeilToInt(Mathf.Max(p0y, Mathf.Max(p1y, p2y))), 0, textureSize - 1);
            if (maxX < minX || maxY < minY) continue;

            float d = (p1y - p2y) * (p0x - p2x) + (p2x - p1x) * (p0y - p2y);
            if (Mathf.Abs(d) < 1e-7f) continue;
            float invD = 1f / d;

            for (int y = minY; y <= maxY; y++)
            {
                float py = y + 0.5f;
                int row = y * textureSize;
                for (int x = minX; x <= maxX; x++)
                {
                    float px = x + 0.5f;
                    float a = ((p1y - p2y) * (px - p2x) + (p2x - p1x) * (py - p2y)) * invD;
                    if (a < eps) continue;
                    float b = ((p2y - p0y) * (px - p2x) + (p0x - p2x) * (py - p2y)) * invD;
                    if (b < eps) continue;
                    if (1f - a - b < eps) continue;
                    mask[row + x] = true;
                }
            }
        }

        _islandMask = mask;
        return mask;
    }

    /// <summary>Builds the per-map seed colors (in canonical/material layout) from the existing material.</summary>
    private void BuildSeedColors()
    {
        _seedCanonical = new Color32[MAP_COUNT][];
        _seedCanonical[MAP_ALBEDO] = BuildBaseColors();

        // Mask map seed from the material scalars: R = metallic, G = occlusion/height, B = 0,
        // A = smoothness. G = 128 (= 0.5) is the NEUTRAL height: no parallax/relief and AO =
        // saturate(2*0.5) = 1 (no darkening), so the unpainted look is unchanged. Painting G
        // below 0.5 carves a hole (and darkens), above 0.5 raises a hill (see PlayerCamoLit).
        float metallic0 = GetMatFloat(MetallicId, 0f);
        float smoothness0 = GetMatFloat(SmoothnessId, 0.5f);
        _seedCanonical[MAP_MSO] = FillCanonical(new Color32(
            (byte)(Mathf.Clamp01(metallic0) * 255f), 128, 0, (byte)(Mathf.Clamp01(smoothness0) * 255f)));

        // Emission: keep the existing look (black if the material's emission is off).
        Color emission0 = Color.black;
        if (_materialInstance.HasProperty(EmissionColorId) &&
            (_materialInstance.globalIlluminationFlags & MaterialGlobalIlluminationFlags.EmissiveIsBlack) == 0)
            emission0 = _materialInstance.GetColor(EmissionColorId);
        _seedCanonical[MAP_EM] = FillCanonical(new Color32(
            (byte)(Mathf.Clamp01(emission0.r) * 255f),
            (byte)(Mathf.Clamp01(emission0.g) * 255f),
            (byte)(Mathf.Clamp01(emission0.b) * 255f), 255));

        // Fur: R = 0 so a fresh avatar has NO fur (R is painted-in length, not coverage, so it is never
        // island-stamped - see SeedGpuMap). G/B/A unused. The strand colour comes from the albedo map.
        _seedCanonical[MAP_FUR] = FillCanonical(new Color32(0, 0, 0, 0));
    }

    private Color32[] FillCanonical(Color32 c)
    {
        var px = new Color32[textureSize * textureSize];
        for (int i = 0; i < px.Length; i++) px[i] = c;
        return px;
    }

    /// <summary>Builds the albedo base-color texels from the existing material texture or baseColor.</summary>
    private Color32[] BuildBaseColors()
    {
        Texture sourceTex = null;
        var shared = _renderer.sharedMaterial;
        if (shared)
        {
            if (shared.HasProperty(BaseMapId)) sourceTex = shared.GetTexture(BaseMapId);
            if (!sourceTex && shared.HasProperty(MainTexId)) sourceTex = shared.GetTexture(MainTexId);
        }

        var src = sourceTex as Texture2D;
        if (src)
        {
            try
            {
                if (src.width == textureSize && src.height == textureSize && src.isReadable)
                    return src.GetPixels32();
            }
            catch { /* not readable -> fall back to baseColor */ }
        }

        return FillCanonical(baseColor);
    }

    /// <summary>Enables the URP keywords for the painted PBR maps and seeds the material scalars.</summary>
    private void ConfigureMaterialPbr()
    {
        if (!_materialInstance) return;

        // Metallic-smoothness map: metallic from R, smoothness from the map's alpha
        // (NOT the albedo alpha) scaled by _Smoothness (= 1 so the map drives it as-is).
        if (_materialInstance.HasProperty(MetallicGlossMapId))
        {
            _materialInstance.EnableKeyword("_METALLICSPECGLOSSMAP");
            _materialInstance.DisableKeyword("_SMOOTHNESS_TEXTURE_ALBEDO_CHANNEL_A");
            SetMatFloat(SmoothnessId, 1f);
        }

        // Emission map x _EmissionColor (white * intensity). Clear the "emissive is black"
        // GI flag so the emission is actually used.
        if (_materialInstance.HasProperty(EmissionMapId))
        {
            _materialInstance.EnableKeyword("_EMISSION");
            _materialInstance.globalIlluminationFlags = MaterialGlobalIlluminationFlags.RealtimeEmissive;
            _lastEmissionIntensity = float.NaN; // fresh material instance -> force the first write
            RefreshEmissionColor();
        }

        // Occlusion map: URP samples the G channel (LerpWhiteTo(map.g, _OcclusionStrength)).
        // Strength 1 so the painted value drives the occlusion as-is.
        if (_materialInstance.HasProperty(OcclusionMapId))
        {
            _materialInstance.EnableKeyword("_OCCLUSIONMAP");
            SetMatFloat(OcclusionStrengthId, 1f);
        }

        // Height: the same mask map is also bound to _ParallaxMap, so the painted occlusion (G) doubles
        // as a 0.5-centred height. _PARALLAXMAP enables URP's parallax AND our relief-normal/AO remap in
        // PlayerCamoLit; _Parallax is lifted off its floor so the displacement is visible. _NORMALMAP is
        // REQUIRED for the relief normal to show - URP only transforms normalTS into world space when it
        // (or _DETAIL) is set, otherwise the relief is invisible. _BumpMap stays unbound (flat default
        // normal), so the keyword only enables the tangent->world path.
        if (_materialInstance.HasProperty(ParallaxMapId))
        {
            _materialInstance.EnableKeyword("_PARALLAXMAP");
            _materialInstance.EnableKeyword("_NORMALMAP");
            if (GetMatFloat(ParallaxId, ParallaxBase) < ParallaxBase)
                SetMatFloat(ParallaxId, ParallaxBase);
        }
    }

    private float _lastEmissionIntensity = float.NaN;

    /// <summary>Pushes the global emission intensity to the material's _EmissionColor (live-tunable).
    /// Runs per frame, so it only writes the material when the intensity actually changed.</summary>
    private void RefreshEmissionColor()
    {
        if (emissionIntensity == _lastEmissionIntensity) return;
        if (_materialInstance && _materialInstance.HasProperty(EmissionColorId))
        {
            _materialInstance.SetColor(EmissionColorId, Color.white * Mathf.Max(0f, emissionIntensity));
            _lastEmissionIntensity = emissionIntensity;
        }
    }

    /// <summary>Eases the see-through X-ray glow's alpha toward its on/off target (<see cref="XRayRevealed"/>)
    /// at a constant rate, so the reveal fades in/out over <c>xrayFadeDuration</c> seconds instead of popping.
    /// Rgb is left untouched (the authored glow colour). Only writes the material on an actual change, and
    /// snaps instantly when the duration is 0.</summary>
    private void TickXRayFade()
    {
        if (!_materialInstance || !_materialInstance.HasProperty(XRayColorId)) return;
        Color c = _materialInstance.GetColor(XRayColorId);
        float step = xrayFadeDuration > 0f ? Time.deltaTime / xrayFadeDuration : 1f;
        float a = Mathf.MoveTowards(c.a, _xrayTarget, step);
        if (a == c.a) return; // already at target -> no material write
        c.a = a;
        _materialInstance.SetColor(XRayColorId, c);
    }

    /// <summary>Applies the current hit-flash state to the X-ray material: flash mode boosts the authored glow
    /// rgb by <c>xrayFlashBoost</c>, turns the breathing pulse off (steady), and snaps the reveal alpha on for an
    /// immediate pop; leaving flash restores the authored rgb + pulse (alpha keeps easing via TickXRayFade). The
    /// pulse plateau otherwise leaves a short hit window looking dim, so a steady boosted glow reads far stronger.</summary>
    private void ApplyXRayFlashState()
    {
        if (!_materialInstance || !_materialInstance.HasProperty(XRayColorId)) return;
        float boost = _xrayFlash ? Mathf.Max(1f, xrayFlashBoost) : 1f;
        Color c = _materialInstance.GetColor(XRayColorId);
        c.r = _xrayBaseColor.r * boost;
        c.g = _xrayBaseColor.g * boost;
        c.b = _xrayBaseColor.b * boost;
        if (_xrayFlash) c.a = _xrayTarget; // snap the glow on so the hit reads instantly (no ramp-in)
        _materialInstance.SetColor(XRayColorId, c);
        if (_materialInstance.HasProperty(XRayPulseStrengthId))
            _materialInstance.SetFloat(XRayPulseStrengthId, _xrayFlash ? 0f : _xrayBasePulseStrength);
    }
}