using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Numerics;
using AcDream.Content;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using DatReaderWriter.Lib.IO;
using DatReaderWriter.Types;
using Microsoft.Extensions.Logging.Abstractions;

namespace AcDream.Content.Tests;

/// <summary>
/// #426 (2026-08-23, the Holtburg windmill axle 0x010010CE, 8 polygons all
/// NoPos + Base1Solid): MeshExtractor.PrepareGfxObjMeshData used to gate the
/// positive side on <c>!Stippling.NoPos</c>, dropping every solid-colour
/// polygon on every object client-wide (NoPos means "no positive UVs" —
/// acclient.h:7386 — not "no positive face"). These tests exercise the fix
/// through the PUBLIC PrepareMeshData entry point against a synthetic,
/// entirely in-memory dat graph (no installed DAT directory required — this
/// lane stays hermetic), using a hand-rolled <see cref="IDatReaderWriter"/> /
/// <see cref="IDatDatabase"/> pair in the same shape as
/// DatResolutionPrecedenceTests' ResolutionSource/StubDatabase.
/// </summary>
public sealed class MeshExtractorSolidFaceExtractionTests
{
    private const uint GfxObjId = 0x01000001u;
    private const uint SolidSurfaceId = 0x08000001u;
    private const uint TexturedSurfaceId = 0x08000002u;
    private const uint SurfaceTextureId = 0x05000001u;
    private const uint RenderSurfaceId = 0x06000001u;

    /// <summary>
    /// One quad polygon, NoPos + Base1Solid: the exact shape of the windmill
    /// axle's own polygons. Must now extract to 4 vertices / 6 indices in a
    /// single batch flagged solid, instead of the pre-#426 0-vertex mesh.
    /// </summary>
    [Fact]
    public void PrepareMeshData_NoPosSolidQuad_EmitsSolidBatchWithFourVerticesAndSixIndices()
    {
        var dats = new FakeMeshExtractorDats();
        dats.RegisterRootGfxObj(GfxObjId, BuildQuadGfxObj(SolidSurfaceId, noPos: true));
        var color = new ColorARGB { Alpha = 255, Red = 12, Green = 34, Blue = 56 };
        dats.Register(SolidSurfaceId, new Surface
        {
            Type = SurfaceType.Base1Solid,
            ColorValue = color,
        });

        var extractor = new MeshExtractor(dats, NullLogger.Instance, sideStagedSink: null);

        ObjectMeshData? mesh = extractor.PrepareMeshData(GfxObjId, isSetup: false);

        Assert.NotNull(mesh);
        Assert.Equal(4, mesh!.Vertices.Length);
        List<TextureBatchData> batches = mesh.TextureBatches.Values.Single();
        TextureBatchData batch = Assert.Single(batches);
        Assert.Equal(6, batch.Indices.Count);
        Assert.True(batch.Key.IsSolid);

        // GetOrCreateSolidColorTexture bakes the surface's own ColorValue.
        Assert.Equal((byte)color.Red, batch.TextureData[0]);
        Assert.Equal((byte)color.Green, batch.TextureData[1]);
        Assert.Equal((byte)color.Blue, batch.TextureData[2]);
        Assert.Equal((byte)color.Alpha, batch.TextureData[3]);
    }

    /// <summary>
    /// Same NoPos quad, but the positive surface is TEXTURED
    /// (Base1Image) rather than solid. NoPos still means "no UVs on this
    /// polygon's wire data" regardless of what the surface is — the emitted
    /// vertices fall back to UV (0,0), and the batch must be classified
    /// non-solid (IsSolid == false) so it decodes the real texture instead
    /// of baking a flat colour fill.
    /// </summary>
    [Fact]
    public void PrepareMeshData_NoPosTexturedQuad_EmitsWithZeroUVsAndIsSolidFalse()
    {
        var dats = new FakeMeshExtractorDats();
        dats.RegisterRootGfxObj(GfxObjId, BuildQuadGfxObj(TexturedSurfaceId, noPos: true));
        dats.Register(TexturedSurfaceId, new Surface
        {
            Type = SurfaceType.Base1Image,
            OrigTextureId = SurfaceTextureId,
        });
        dats.Register(SurfaceTextureId, new SurfaceTexture
        {
            Textures = new List<QualifiedDataId<RenderSurface>> { RenderSurfaceId },
        });
        dats.Register(RenderSurfaceId, new RenderSurface
        {
            Width = 1,
            Height = 1,
            Format = PixelFormat.PFID_A8R8G8B8,
            SourceData = new byte[] { 10, 20, 30, 255 },
        });

        var extractor = new MeshExtractor(dats, NullLogger.Instance, sideStagedSink: null);

        ObjectMeshData? mesh = extractor.PrepareMeshData(GfxObjId, isSetup: false);

        Assert.NotNull(mesh);
        Assert.Equal(4, mesh!.Vertices.Length);
        Assert.All(mesh.Vertices, v => Assert.Equal(Vector2.Zero, v.UV));

        List<TextureBatchData> batches = mesh.TextureBatches.Values.Single();
        TextureBatchData batch = Assert.Single(batches);
        Assert.Equal(6, batch.Indices.Count);
        Assert.False(batch.Key.IsSolid);
    }

    /// <summary>One quad (4 verts), single polygon, PosSurface referencing <paramref name="surfaceId"/>.</summary>
    private static GfxObj BuildQuadGfxObj(uint surfaceId, bool noPos)
    {
        return new GfxObj
        {
            Surfaces = { surfaceId },
            VertexArray = new VertexArray
            {
                Vertices =
                {
                    // No UVs at all — matches a real NoPos polygon's vertices,
                    // which carry no UV entries because nothing samples them.
                    [0] = new SWVertex { Origin = new Vector3(0, 0, 0), Normal = Vector3.UnitZ },
                    [1] = new SWVertex { Origin = new Vector3(1, 0, 0), Normal = Vector3.UnitZ },
                    [2] = new SWVertex { Origin = new Vector3(1, 1, 0), Normal = Vector3.UnitZ },
                    [3] = new SWVertex { Origin = new Vector3(0, 1, 0), Normal = Vector3.UnitZ },
                },
            },
            Polygons =
            {
                [0] = new Polygon
                {
                    Stippling = noPos ? StipplingType.NoPos : default,
                    PosSurface = 0,
                    NegSurface = -1,
                    VertexIds = { 0, 1, 2, 3 },
                },
            },
        };
    }

    /// <summary>
    /// Minimal in-memory <see cref="IDatReaderWriter"/> for MeshExtractor:
    /// resolves exactly one "root" GfxObj through Portal (the only path
    /// PrepareMeshData needs for TryResolvePreferred's default
    /// implementation), plus arbitrary typed lookups (Surface,
    /// SurfaceTexture, RenderSurface) also through Portal.
    /// </summary>
    private sealed class FakeMeshExtractorDats : IDatReaderWriter
    {
        private readonly Dictionary<uint, IDBObj> _portalObjects = new();
        private uint _rootId;

        public FakeMeshExtractorDats() => Portal = new FakeDatDatabase(_portalObjects);

        public void RegisterRootGfxObj(uint id, GfxObj gfxObj)
        {
            _rootId = id;
            _portalObjects[id] = gfxObj;
        }

        public void Register<T>(uint id, T obj) where T : IDBObj => _portalObjects[id] = obj;

        public string SourceDirectory => string.Empty;
        public IDatDatabase Portal { get; }
        public IDatDatabase Cell => EmptyDatDatabase.Instance;
        public ReadOnlyDictionary<uint, IDatDatabase> CellRegions { get; } =
            new(new Dictionary<uint, IDatDatabase>());
        public IDatDatabase HighRes => EmptyDatDatabase.Instance;
        public IDatDatabase Language => EmptyDatDatabase.Instance;
        public IDatDatabase Local => EmptyDatDatabase.Instance;
        public ReadOnlyDictionary<uint, uint> RegionFileMap { get; } =
            new(new Dictionary<uint, uint>());
        public int PortalIteration => 0;
        public int CellIteration => 0;
        public int HighResIteration => 0;
        public int LanguageIteration => 0;

        public bool TryGetFileBytes(uint regionId, uint fileId, ref byte[] bytes, out int bytesRead)
        {
            bytesRead = 0;
            return false;
        }

        public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj => Array.Empty<uint>();

        public IEnumerable<IDatReaderWriter.IdResolution> ResolveId(uint id) =>
            id == _rootId
                ? new[] { new IDatReaderWriter.IdResolution(Portal, DBObjType.GfxObj) }
                : Array.Empty<IDatReaderWriter.IdResolution>();

        public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
            throw new NotSupportedException();

        public bool TrySave<T>(uint regionId, T obj, int iteration = 0) where T : IDBObj =>
            throw new NotSupportedException();

        [return: MaybeNull]
        public T Get<T>(uint fileId) where T : IDBObj =>
            Portal.TryGet<T>(fileId, out var value) ? value : default;

        public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value) where T : IDBObj =>
            Portal.TryGet(fileId, out value);

        public void Dispose()
        {
        }
    }

    private sealed class FakeDatDatabase : IDatDatabase
    {
        private readonly Dictionary<uint, IDBObj> _objects;

        public FakeDatDatabase(Dictionary<uint, IDBObj> objects) => _objects = objects;

        // Never dereferenced by MeshExtractor's own code paths (only
        // RetailPhysicsScriptLoader's ctor reads it, into a NULLABLE field
        // it never touches unless a physics-script emitter is loaded, which
        // these tests never trigger).
        public DatDatabase Db => null!;
        public int Iteration => 0;

        public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj => Array.Empty<uint>();

        public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value) where T : IDBObj
        {
            if (_objects.TryGetValue(fileId, out IDBObj? obj) && obj is T typed)
            {
                value = typed;
                return true;
            }
            value = default;
            return false;
        }

        public bool TryGetFileBytes(uint fileId, [MaybeNullWhen(false)] out byte[] value)
        {
            value = null;
            return false;
        }

        public bool TryGetFileBytes(uint fileId, ref byte[] bytes, out int bytesRead)
        {
            bytesRead = 0;
            return false;
        }

        public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
            throw new NotSupportedException();

        public void Dispose()
        {
        }
    }

    private sealed class EmptyDatDatabase : IDatDatabase
    {
        public static readonly EmptyDatDatabase Instance = new();

        public DatDatabase Db => null!;
        public int Iteration => 0;

        public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj => Array.Empty<uint>();

        public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value) where T : IDBObj
        {
            value = default;
            return false;
        }

        public bool TryGetFileBytes(uint fileId, [MaybeNullWhen(false)] out byte[] value)
        {
            value = null;
            return false;
        }

        public bool TryGetFileBytes(uint fileId, ref byte[] bytes, out int bytesRead)
        {
            bytesRead = 0;
            return false;
        }

        public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
            throw new NotSupportedException();

        public void Dispose()
        {
        }
    }
}