using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Drawing;
using SixLabors.ImageSharp.Drawing.Processing;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Numerics;

namespace AssetStudio
{
    public static class SpriteHelper
    {
        public static Image<Bgra32> GetImage(this Sprite m_Sprite)
        {
            if (m_Sprite.m_SpriteAtlas != null && m_Sprite.m_SpriteAtlas.TryGet(out var m_SpriteAtlas))
            {
                if (m_SpriteAtlas.m_RenderDataMap.TryGetValue(m_Sprite.m_RenderDataKey, out var spriteAtlasData) && spriteAtlasData.texture.TryGet(out var m_Texture2D))
                {
                    return CutImage(m_Sprite, m_Texture2D, spriteAtlasData.textureRect, spriteAtlasData.textureRectOffset, spriteAtlasData.downscaleMultiplier, spriteAtlasData.settingsRaw);
                }
            }
            else
            {
                if (m_Sprite.m_RD.texture.TryGet(out var m_Texture2D))
                {
                    return CutImage(m_Sprite, m_Texture2D, m_Sprite.m_RD.textureRect, m_Sprite.m_RD.textureRectOffset, m_Sprite.m_RD.downscaleMultiplier, m_Sprite.m_RD.settingsRaw);
                }
            }
            return null;
        }

        private static Image<Bgra32> CutImage(Sprite m_Sprite, Texture2D m_Texture2D, Rectf textureRect, Vector2 textureRectOffset, float downscaleMultiplier, SpriteSettings settingsRaw)
        {
            var originalImage = m_Texture2D.ConvertToImage(false);
            if (originalImage != null)
            {
                using (originalImage)
                {
                    if (downscaleMultiplier > 0f && downscaleMultiplier != 1f)
                    {
                        var width = (int)(m_Texture2D.m_Width / downscaleMultiplier);
                        var height = (int)(m_Texture2D.m_Height / downscaleMultiplier);
                        originalImage.Mutate(x => x.Resize(width, height));
                    }
                    var rectX = (int)Math.Floor(textureRect.x);
                    var rectY = (int)Math.Floor(textureRect.y);
                    var rectRight = (int)Math.Ceiling(textureRect.x + textureRect.width);
                    var rectBottom = (int)Math.Ceiling(textureRect.y + textureRect.height);
                    rectRight = Math.Min(rectRight, originalImage.Width);
                    rectBottom = Math.Min(rectBottom, originalImage.Height);
                    var rect = new Rectangle(rectX, rectY, rectRight - rectX, rectBottom - rectY);
                    var spriteImage = originalImage.Clone(x => x.Crop(rect));
                    if (settingsRaw.packed == 1)
                    {
                        //RotateAndFlip
                        switch (settingsRaw.packingRotation)
                        {
                            case SpritePackingRotation.FlipHorizontal:
                                spriteImage.Mutate(x => x.Flip(FlipMode.Horizontal));
                                break;
                            case SpritePackingRotation.FlipVertical:
                                spriteImage.Mutate(x => x.Flip(FlipMode.Vertical));
                                break;
                            case SpritePackingRotation.Rotate180:
                                spriteImage.Mutate(x => x.Rotate(180));
                                break;
                            case SpritePackingRotation.Rotate90:
                                spriteImage.Mutate(x => x.Rotate(270));
                                break;
                        }
                    }

                    //Tight
                    if (settingsRaw.packingMode == SpritePackingMode.Tight)
                    {
                        try
                        {
                            var triangles = GetTriangles(m_Sprite.m_RD);
                            var polygons = triangles.Select(x => new Polygon(new LinearLineSegment(x.Select(y => new PointF(y.X, y.Y)).ToArray()))).ToArray();
                            IPathCollection path = new PathCollection(polygons);
                            var matrix = Matrix3x2.CreateScale(m_Sprite.m_PixelsToUnits);
                            matrix *= Matrix3x2.CreateTranslation(m_Sprite.m_Rect.width * m_Sprite.m_Pivot.X - textureRectOffset.X, m_Sprite.m_Rect.height * m_Sprite.m_Pivot.Y - textureRectOffset.Y);
                            path = path.Transform(matrix);
                            var options = new DrawingOptions
                            {
                                GraphicsOptions = new GraphicsOptions
                                {
                                    Antialias = false,
                                    AlphaCompositionMode = PixelAlphaCompositionMode.DestOut
                                }
                            };
                            using (var mask = new Image<Bgra32>(rect.Width, rect.Height, SixLabors.ImageSharp.Color.Black))
                            {
                                mask.Mutate(x => x.Fill(options, SixLabors.ImageSharp.Color.Red, path));
                                var bursh = new ImageBrush(mask);
                                spriteImage.Mutate(x => x.Fill(options, bursh));
                                spriteImage.Mutate(x => x.Flip(FlipMode.Vertical));
                                return spriteImage;
                            }
                        }
                        catch
                        {
                            // ignored
                        }
                    }

                    //Rectangle
                    spriteImage.Mutate(x => x.Flip(FlipMode.Vertical));
                    return spriteImage;
                }
            }

            return null;
        }

        private static Vector2[][] GetTriangles(SpriteRenderData m_RD)
        {
            if (m_RD.vertices != null) //5.6 down
            {
                var vertices = m_RD.vertices.Select(x => (Vector2)x.pos).ToArray();
                var triangleCount = m_RD.indices.Length / 3;
                var triangles = new Vector2[triangleCount][];
                for (int i = 0; i < triangleCount; i++)
                {
                    var first = m_RD.indices[i * 3];
                    var second = m_RD.indices[i * 3 + 1];
                    var third = m_RD.indices[i * 3 + 2];
                    var triangle = new[] { vertices[first], vertices[second], vertices[third] };
                    triangles[i] = triangle;
                }
                return triangles;
            }
            else //5.6 and up
            {
                var triangles = new List<Vector2[]>();
                var m_VertexData = m_RD.m_VertexData;
                var m_Channel = m_VertexData.m_Channels[0]; //kShaderChannelVertex
                var m_Stream = m_VertexData.m_Streams[m_Channel.stream];
                using (var vertexReader = new BinaryReader(new MemoryStream(m_VertexData.m_DataSize)))
                {
                    using (var indexReader = new BinaryReader(new MemoryStream(m_RD.m_IndexBuffer)))
                    {
                        foreach (var subMesh in m_RD.m_SubMeshes)
                        {
                            vertexReader.BaseStream.Position = m_Stream.offset + subMesh.firstVertex * m_Stream.stride + m_Channel.offset;

                            var vertices = new Vector2[subMesh.vertexCount];
                            for (int v = 0; v < subMesh.vertexCount; v++)
                            {
                                vertices[v] = vertexReader.ReadVector3();
                                vertexReader.BaseStream.Position += m_Stream.stride - 12;
                            }

                            indexReader.BaseStream.Position = subMesh.firstByte;

                            var triangleCount = subMesh.indexCount / 3u;
                            for (int i = 0; i < triangleCount; i++)
                            {
                                var first = indexReader.ReadUInt16() - subMesh.firstVertex;
                                var second = indexReader.ReadUInt16() - subMesh.firstVertex;
                                var third = indexReader.ReadUInt16() - subMesh.firstVertex;
                                var triangle = new[] { vertices[first], vertices[second], vertices[third] };
                                triangles.Add(triangle);
                            }
                        }
                    }
                }
                return triangles.ToArray();
            }
        }
    }
}