using AssetRipper.Numerics;
using AssetRipper.SourceGenerated.Classes.ClassID_43;
using System.Numerics;
using System.Runtime.CompilerServices;

namespace AssetRipper.SourceGenerated.Extensions;

public readonly record struct MeshData(
	Vector3[] Vertices,
	Vector3[]? Normals,
	Vector4[]? Tangents,
	ColorFloat[]? Colors,
	Vector2[]? UV0,
	Vector2[]? UV1,
	Vector2[]? UV2,
	Vector2[]? UV3,
	Vector2[]? UV4,
	Vector2[]? UV5,
	Vector2[]? UV6,
	Vector2[]? UV7,
	BoneWeight4[]? Skin,
	uint[] ProcessedIndexBuffer)
{
	public static MeshData Empty => new([], null, null, null, null, null, null, null, null, null, null, null, null, []);

	[MemberNotNullWhen(true, nameof(Normals))]
	public bool HasNormals => Normals != null && Normals.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(Tangents))]
	public bool HasTangents => Tangents != null && Tangents.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(Colors))]
	public bool HasColors => Colors != null && Colors.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV0))]
	public bool HasUV0 => UV0 != null && UV0.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV1))]
	public bool HasUV1 => UV1 != null && UV1.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV2))]
	public bool HasUV2 => UV2 != null && UV2.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV3))]
	public bool HasUV3 => UV3 != null && UV3.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV4))]
	public bool HasUV4 => UV4 != null && UV4.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV5))]
	public bool HasUV5 => UV5 != null && UV5.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV6))]
	public bool HasUV6 => UV6 != null && UV6.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(UV7))]
	public bool HasUV7 => UV7 != null && UV7.Length == Vertices.Length;

	[MemberNotNullWhen(true, nameof(Skin))]
	public bool HasSkin => Skin != null && Skin.Length == Vertices.Length;

	public int UVCount
	{
		get
		{
			if (UV0 is null || UV0.Length != Vertices.Length)
			{
				return 0;
			}
			else if (UV1 is null || UV1.Length != Vertices.Length)
			{
				return 1;
			}
			else if (UV2 is null || UV2.Length != Vertices.Length)
			{
				return 2;
			}
			else if (UV3 is null || UV3.Length != Vertices.Length)
			{
				return 3;
			}
			else if (UV4 is null || UV4.Length != Vertices.Length)
			{
				return 4;
			}
			else if (UV5 is null || UV5.Length != Vertices.Length)
			{
				return 5;
			}
			else if (UV6 is null || UV6.Length != Vertices.Length)
			{
				return 6;
			}
			else if (UV7 is null || UV7.Length != Vertices.Length)
			{
				return 7;
			}
			else
			{
				return 8;
			}
		}
	}

	public Vector3 TryGetVertexAtIndex(uint index) => Vertices[index];
	public Vector3 TryGetNormalAtIndex(uint index) => TryGetAtIndex(Normals, index);
	public Vector4 TryGetTangentAtIndex(uint index)
	{
		Vector4 v = TryGetAtIndex(Tangents, index);
		//Unity documentation claims W should always be 1 or -1, but it's not always the case.
		return v.W switch
		{
			-1 or 1 => v,
			< 0 => new Vector4(v.X, v.Y, v.Z, -1),
			_ => new Vector4(v.X, v.Y, v.Z, 1)
		};
	}
	public ColorFloat TryGetColorAtIndex(uint index) => TryGetAtIndex(Colors, index);
	public Vector2 TryGetUV0AtIndex(uint index) => FlipY(TryGetAtIndex(UV0, index));
	public Vector2 TryGetUV1AtIndex(uint index) => FlipY(TryGetAtIndex(UV1, index));
	public Vector2 TryGetUV2AtIndex(uint index) => FlipY(TryGetAtIndex(UV2, index));
	public Vector2 TryGetUV3AtIndex(uint index) => FlipY(TryGetAtIndex(UV3, index));
	public Vector2 TryGetUV4AtIndex(uint index) => FlipY(TryGetAtIndex(UV4, index));
	public Vector2 TryGetUV5AtIndex(uint index) => FlipY(TryGetAtIndex(UV5, index));
	public Vector2 TryGetUV6AtIndex(uint index) => FlipY(TryGetAtIndex(UV6, index));
	public Vector2 TryGetUV7AtIndex(uint index) => FlipY(TryGetAtIndex(UV7, index));
	public BoneWeight4 TryGetSkinAtIndex(uint index)
	{
		BoneWeight4 s = TryGetAtIndex(Skin, index);
		if (s == default || s.AnyWeightsNegative)
		{
			//Invalid bone weights, set to a valid default.
			return new BoneWeight4(.25f, .25f, .25f, .25f, 0, 0, 0, 0);
		}
		else if (s.Sum != 1)
		{
			return s.NormalizeWeights();
		}
		else
		{
			return s;
		}
	}

	private static Vector2 FlipY(Vector2 uv) => new Vector2(uv.X, 1 - uv.Y);

	public static bool TryMakeFromMesh(IMesh mesh, out MeshData meshData)
	{
		mesh.ReadData(
			out Vector3[]? vertices,
			out Vector3[]? normals,
			out Vector4[]? tangents,
			out ColorFloat[]? colors,
			out BoneWeight4[]? skin,
			out Vector2[]? uv0,
			out Vector2[]? uv1,
			out Vector2[]? uv2,
			out Vector2[]? uv3,
			out Vector2[]? uv4,
			out Vector2[]? uv5,
			out Vector2[]? uv6,
			out Vector2[]? uv7,
			out _, //bindpose
			out uint[] processedIndexBuffer);

		if (vertices is null)
		{
			meshData = default;
			return false;
		}
		else
		{
			meshData = new MeshData(vertices, normals, tangents, colors, uv0, uv1, uv2, uv3, uv4, uv5, uv6, uv7, skin, processedIndexBuffer);
			return true;
		}
	}

	[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
	private static T TryGetAtIndex<T>(T[]? array, uint index) where T : struct
	{
		return array is null ? default : array[index];
	}
}