using System.IO;
using System.Linq;
using System.Text;
using Godot;

namespace KeepersCompound.TMV;

public partial class TextureLoader
{
    // TODO: Support more types of PCX just in case

    // References:
    // - https://www.fileformat.info/format/pcx/egff.htm
    // - http://www.fysnet.net/pcxfile.htm
    private static Image LoadPcx(string path)
    {
        static Color[] LoadFamilyPalette(string famPath)
        {
            var numColors = 256;
            var bytesPerColor = 3;
            var paletteSize = numColors * bytesPerColor;
            var palette = new Color[numColors];

            var options = new EnumerationOptions
            {
                MatchCasing = MatchCasing.CaseInsensitive
            };
            var paths = Directory.GetFiles(famPath, "full.pcx", options);
            if (paths.Length != 0)
            {
                var palettePath = paths[0];
                using MemoryStream stream = new(File.ReadAllBytes(palettePath));
                using BinaryReader reader = new(stream, Encoding.UTF8, false);
                stream.Seek(-paletteSize, SeekOrigin.End);

                for (var i = 0; i < numColors; i++)
                {
                    var r = reader.ReadByte() / 255.0f;
                    var g = reader.ReadByte() / 255.0f;
                    var b = reader.ReadByte() / 255.0f;
                    var a = (i == 0) ? 0.0f : 1.0f;
                    palette[i] = new Color(r, g, b, a);
                }
            }

            return palette;
        }

        static System.Numerics.Vector2 ReadVec2(BinaryReader reader)
        {
            return new(reader.ReadUInt16(), reader.ReadUInt16());
        }

        using MemoryStream stream = new(File.ReadAllBytes(path));
        using BinaryReader reader = new(stream, Encoding.UTF8, false);

        // Header
        var tag = reader.ReadByte();
        var version = reader.ReadByte();
        var compression = reader.ReadByte();
        var bytesPerPixel = reader.ReadByte();
        var min = ReadVec2(reader);
        var max = ReadVec2(reader);
        var dpi = ReadVec2(reader);
        var headerPalette = reader.ReadBytes(48);
        reader.ReadByte();
        var numPlanes = reader.ReadByte();
        var bytesPerRow = reader.ReadUInt16();
        var paletteMode = reader.ReadUInt16();
        var dpiSrc = ReadVec2(reader);
        reader.ReadBytes(54);

        // Validation
        if (tag != 0x0A)
        {
            throw new System.Exception("Invalid tag");
        }
        var validVersions = new int[] { 0, 2, 3, 4, 5 };
        if (!validVersions.Contains(version))
        {
            throw new System.Exception("Unsupported version");
        }
        if (compression != 1)
        {
            throw new System.Exception("Unsupported compression mode");
        }
        if (bytesPerPixel != 8 || numPlanes != 1)
        {
            throw new System.Exception("Unsupported bpp/plane format");
        }

        var palette = LoadFamilyPalette(path.GetBaseDir());

        // Read run length encoded pixel Data
        var width = (int)(max.X - min.X + 1);
        var height = (int)(max.Y - min.Y + 1);
        var image = Image.CreateEmpty(width, height, false, Image.Format.Rgba8);
        for (var y = 0; y < height; y++)
        {
            var x = 0;
            while (x < bytesPerRow)
            {
                var b = reader.ReadByte();
                if ((b & 0xc0) == 0xc0)
                {
                    var runLength = b & 0x3f;
                    b = reader.ReadByte();
                    for (var i = 0; i < runLength; i++)
                    {
                        image.SetPixel(x, y, palette[b]);
                        x++;
                    }
                }
                else
                {
                    image.SetPixel(x, y, palette[b]);
                    x++;
                }
            }
        }

        return image;
    }
}