using System;
using System.IO;
using System.Reflection;
using System.Text;
using Lumina.Data.Parsing;
using Lumina.Extensions;

namespace Penumbra.GameData.Files;

public partial class MdlFile
{
    public const uint NumVertices    = 17;
    public const uint FileHeaderSize = 0x44;

    // Refers to string, thus not Lumina struct.
    public struct Shape
    {
        public string   ShapeName = string.Empty;
        public ushort[] ShapeMeshStartIndex;
        public ushort[] ShapeMeshCount;

        public Shape( MdlStructs.ShapeStruct data, uint[] offsets, string[] strings )
        {
            var idx = offsets.AsSpan().IndexOf( data.StringOffset );
            ShapeName           = idx >= 0 ? strings[ idx ] : string.Empty;
            ShapeMeshStartIndex = data.ShapeMeshStartIndex;
            ShapeMeshCount      = data.ShapeMeshCount;
        }
    }

    // Raw data to write back.
    public uint   Version;
    public float  Radius;
    public float  ModelClipOutDistance;
    public float  ShadowClipOutDistance;
    public byte   BgChangeMaterialIndex;
    public byte   BgCrestChangeMaterialIndex;
    public ushort Unknown4;
    public byte   Unknown5;
    public byte   Unknown6;
    public ushort Unknown7;
    public ushort Unknown8;
    public ushort Unknown9;

    // Offsets are stored relative to RuntimeSize instead of file start.
    public uint[] VertexOffset;
    public uint[] IndexOffset;

    public uint[] VertexBufferSize;
    public uint[] IndexBufferSize;
    public byte   LodCount;
    public bool   EnableIndexBufferStreaming;
    public bool   EnableEdgeGeometry;


    public MdlStructs.ModelFlags1 Flags1;
    public MdlStructs.ModelFlags2 Flags2;

    public MdlStructs.BoundingBoxStruct BoundingBoxes;
    public MdlStructs.BoundingBoxStruct ModelBoundingBoxes;
    public MdlStructs.BoundingBoxStruct WaterBoundingBoxes;
    public MdlStructs.BoundingBoxStruct VerticalFogBoundingBoxes;

    public MdlStructs.VertexDeclarationStruct[]    VertexDeclarations;
    public MdlStructs.ElementIdStruct[]            ElementIds;
    public MdlStructs.MeshStruct[]                 Meshes;
    public MdlStructs.BoneTableStruct[]            BoneTables;
    public MdlStructs.BoundingBoxStruct[]          BoneBoundingBoxes;
    public MdlStructs.SubmeshStruct[]              SubMeshes;
    public MdlStructs.ShapeMeshStruct[]            ShapeMeshes;
    public MdlStructs.ShapeValueStruct[]           ShapeValues;
    public MdlStructs.TerrainShadowMeshStruct[]    TerrainShadowMeshes;
    public MdlStructs.TerrainShadowSubmeshStruct[] TerrainShadowSubMeshes;
    public MdlStructs.LodStruct[]                  Lods;
    public MdlStructs.ExtraLodStruct[]             ExtraLods;
    public ushort[]                                SubMeshBoneMap;

    // Strings are written in order
    public string[] Attributes;
    public string[] Bones;
    public string[] Materials;
    public Shape[]  Shapes;

    // Raw, unparsed data.
    public byte[] RemainingData;

    public MdlFile( byte[] data )
    {
        using var stream = new MemoryStream( data );
        using var r      = new BinaryReader( stream );

        var header = LoadModelFileHeader( r );
        LodCount         = header.LodCount;
        VertexBufferSize = header.VertexBufferSize;
        IndexBufferSize  = header.IndexBufferSize;
        VertexOffset     = header.VertexOffset;
        IndexOffset      = header.IndexOffset;
        for( var i = 0; i < 3; ++i )
        {
            if( VertexOffset[ i ] > 0 )
            {
                VertexOffset[ i ] -= header.RuntimeSize;
            }

            if( IndexOffset[ i ] > 0 )
            {
                IndexOffset[ i ] -= header.RuntimeSize;
            }
        }

        VertexDeclarations = new MdlStructs.VertexDeclarationStruct[header.VertexDeclarationCount];
        for( var i = 0; i < header.VertexDeclarationCount; ++i )
        {
            VertexDeclarations[ i ] = MdlStructs.VertexDeclarationStruct.Read( r );
        }

        var (offsets, strings) = LoadStrings( r );

        var modelHeader = LoadModelHeader( r );
        ElementIds = new MdlStructs.ElementIdStruct[modelHeader.ElementIdCount];
        for( var i = 0; i < modelHeader.ElementIdCount; i++ )
        {
            ElementIds[ i ] = MdlStructs.ElementIdStruct.Read( r );
        }

        Lods = r.ReadStructuresAsArray< MdlStructs.LodStruct >( 3 );
        ExtraLods = modelHeader.ExtraLodEnabled
            ? r.ReadStructuresAsArray< MdlStructs.ExtraLodStruct >( 3 )
            : Array.Empty< MdlStructs.ExtraLodStruct >();

        Meshes = new MdlStructs.MeshStruct[modelHeader.MeshCount];
        for( var i = 0; i < modelHeader.MeshCount; i++ )
        {
            Meshes[ i ] = MdlStructs.MeshStruct.Read( r );
        }

        Attributes = new string[modelHeader.AttributeCount];
        for( var i = 0; i < modelHeader.AttributeCount; ++i )
        {
            var offset    = r.ReadUInt32();
            var stringIdx = offsets.AsSpan().IndexOf( offset );
            Attributes[ i ] = stringIdx >= 0 ? strings[ stringIdx ] : string.Empty;
        }

        TerrainShadowMeshes    = r.ReadStructuresAsArray< MdlStructs.TerrainShadowMeshStruct >( modelHeader.TerrainShadowMeshCount );
        SubMeshes              = r.ReadStructuresAsArray< MdlStructs.SubmeshStruct >( modelHeader.SubmeshCount );
        TerrainShadowSubMeshes = r.ReadStructuresAsArray< MdlStructs.TerrainShadowSubmeshStruct >( modelHeader.TerrainShadowSubmeshCount );

        Materials = new string[modelHeader.MaterialCount];
        for( var i = 0; i < modelHeader.MaterialCount; ++i )
        {
            var offset    = r.ReadUInt32();
            var stringIdx = offsets.AsSpan().IndexOf( offset );
            Materials[ i ] = stringIdx >= 0 ? strings[ stringIdx ] : string.Empty;
        }

        Bones = new string[modelHeader.BoneCount];
        for( var i = 0; i < modelHeader.BoneCount; ++i )
        {
            var offset    = r.ReadUInt32();
            var stringIdx = offsets.AsSpan().IndexOf( offset );
            Bones[ i ] = stringIdx >= 0 ? strings[ stringIdx ] : string.Empty;
        }

        BoneTables = new MdlStructs.BoneTableStruct[modelHeader.BoneTableCount];
        for( var i = 0; i < modelHeader.BoneTableCount; i++ )
        {
            BoneTables[ i ] = MdlStructs.BoneTableStruct.Read( r );
        }

        Shapes = new Shape[modelHeader.ShapeCount];
        for( var i = 0; i < modelHeader.ShapeCount; i++ )
        {
            Shapes[ i ] = new Shape( MdlStructs.ShapeStruct.Read( r ), offsets, strings );
        }

        ShapeMeshes = r.ReadStructuresAsArray< MdlStructs.ShapeMeshStruct >( modelHeader.ShapeMeshCount );
        ShapeValues = r.ReadStructuresAsArray< MdlStructs.ShapeValueStruct >( modelHeader.ShapeValueCount );

        var submeshBoneMapSize = r.ReadUInt32();
        SubMeshBoneMap = r.ReadStructures< ushort >( ( int )submeshBoneMapSize / 2 ).ToArray();

        var paddingAmount = r.ReadByte();
        r.Seek( r.BaseStream.Position + paddingAmount );

        // Dunno what this first one is for?
        BoundingBoxes            = MdlStructs.BoundingBoxStruct.Read( r );
        ModelBoundingBoxes       = MdlStructs.BoundingBoxStruct.Read( r );
        WaterBoundingBoxes       = MdlStructs.BoundingBoxStruct.Read( r );
        VerticalFogBoundingBoxes = MdlStructs.BoundingBoxStruct.Read( r );
        BoneBoundingBoxes        = new MdlStructs.BoundingBoxStruct[modelHeader.BoneCount];
        for( var i = 0; i < modelHeader.BoneCount; i++ )
        {
            BoneBoundingBoxes[ i ] = MdlStructs.BoundingBoxStruct.Read( r );
        }

        RemainingData = r.ReadBytes( ( int )( r.BaseStream.Length - r.BaseStream.Position ) );
    }

    private MdlStructs.ModelFileHeader LoadModelFileHeader( BinaryReader r )
    {
        var header = MdlStructs.ModelFileHeader.Read( r );
        Version                    = header.Version;
        EnableIndexBufferStreaming = header.EnableIndexBufferStreaming;
        EnableEdgeGeometry         = header.EnableEdgeGeometry;
        return header;
    }

    private MdlStructs.ModelHeader LoadModelHeader( BinaryReader r )
    {
        var modelHeader = r.ReadStructure< MdlStructs.ModelHeader >();
        Radius = modelHeader.Radius;
        Flags1 = ( MdlStructs.ModelFlags1 )( modelHeader.GetType()
               .GetField( "Flags1", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public )?.GetValue( modelHeader )
         ?? 0 );
        Flags2 = ( MdlStructs.ModelFlags2 )( modelHeader.GetType()
               .GetField( "Flags2", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public )?.GetValue( modelHeader )
         ?? 0 );
        ModelClipOutDistance  = modelHeader.ModelClipOutDistance;
        ShadowClipOutDistance = modelHeader.ShadowClipOutDistance;
        Unknown4              = modelHeader.Unknown4;
        Unknown5 = ( byte )( modelHeader.GetType()
               .GetField( "Unknown5", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public )?.GetValue( modelHeader )
         ?? 0 );
        Unknown6                   = modelHeader.Unknown6;
        Unknown7                   = modelHeader.Unknown7;
        Unknown8                   = modelHeader.Unknown8;
        Unknown9                   = modelHeader.Unknown9;
        BgChangeMaterialIndex      = modelHeader.BGChangeMaterialIndex;
        BgCrestChangeMaterialIndex = modelHeader.BGCrestChangeMaterialIndex;

        return modelHeader;
    }

    private static (uint[], string[]) LoadStrings( BinaryReader r )
    {
        var stringCount = r.ReadUInt16();
        r.ReadUInt16();
        var stringSize = ( int )r.ReadUInt32();
        var stringData = r.ReadBytes( stringSize );
        var start      = 0;
        var strings    = new string[stringCount];
        var offsets    = new uint[stringCount];
        for( var i = 0; i < stringCount; ++i )
        {
            var span = stringData.AsSpan( start );
            var idx  = span.IndexOf( ( byte )'\0' );
            strings[ i ] = Encoding.UTF8.GetString( span[ ..idx ] );
            offsets[ i ] = ( uint )start;
            start        = start + idx + 1;
        }

        return ( offsets, strings );
    }

    public unsafe uint StackSize
        => ( uint )( VertexDeclarations.Length * NumVertices * sizeof( MdlStructs.VertexElement ) );

}