using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Xml;
using Quik;
using Quik.Typography;

namespace QuikTestApplication
{
    public class TestFont : QuikFont
    {
        public override QuikFontStyle Style => _style;

        private static QuikFontStyle _style;
        private static HashSet<int> _characters = new HashSet<int>();
        private static Dictionary<int, QuikGlyph> _glyphs = new Dictionary<int, QuikGlyph>();

        public static byte[] TextureData { get; private set; } = Array.Empty<byte>();
        public static QuikVec2 TextureSize { get; private set; }

        public QuikTexture Texture { get; }

        public override float Ascender => throw new NotImplementedException();

        public override float Descender => throw new NotImplementedException();

        public TestFont(QuikContext context)
        {
            Texture = context.TextureManager.CreateTexture(TextureSize, false, QuikImageFormat.RgbaU8);
            unsafe
            {
                fixed (byte* ptr = &TextureData[0])
                {
                    Texture.Image((IntPtr)ptr, QuikImageFormat.RgbaU8, TextureSize, 0);
                }
            }
        }

        static TestFont()
        {
            using (Stream str = typeof(TestFont).Assembly.GetManifestResourceStream("QuikTestApplication.font.xml"))
            {
                XmlDocument document = new XmlDocument();
                document.Load(str);
                
                string family = document.DocumentElement.Attributes["name"].Value;
                float fontSize = float.Parse(document.DocumentElement.Attributes["size"].Value);
                QuikFontType style = QuikFontType.Normal;
                if (document.DocumentElement.Attributes["bold"].Value == "true")
                    style = QuikFontType.Bold;
                if (document.DocumentElement.Attributes["italic"].Value == "true")
                    style = QuikFontType.Italic;

                _style = new QuikFontStyle(family, fontSize, style);
                
                QuikVec2 atlasSize = default;
                atlasSize.X = float.Parse(document.DocumentElement.Attributes["width"].Value);
                atlasSize.Y = float.Parse(document.DocumentElement.Attributes["height"].Value);

                TextureSize = atlasSize;

                foreach (XmlElement element in document.SelectNodes("/font/character"))
                {
                    QuikRectangle UVs;
                    QuikVec2 origin;
                    float advance;
                    int chr = element.Attributes["text"].Value[0];

                    QuikVec2 pos;
                    QuikVec2 size;
                    pos.X = float.Parse(element.Attributes["x"].Value);
                    pos.Y = float.Parse(element.Attributes["y"].Value);
                    size.X = float.Parse(element.Attributes["width"].Value);
                    size.Y = float.Parse(element.Attributes["height"].Value);
                    UVs = new QuikRectangle(
                        (pos.X + size.X)/atlasSize.X, 
                        pos.Y/atlasSize.Y,
                        pos.X/atlasSize.X,
                        (size.Y + pos.Y)/atlasSize.Y);

                    origin.X = float.Parse(element.Attributes["origin-x"].Value);
                    origin.Y = float.Parse(element.Attributes["origin-y"].Value);

                    advance = float.Parse(element.Attributes["advance"].Value);

                    QuikGlyph glyph = new QuikGlyph(chr, UVs, size, origin, default, new QuikVec2(advance, 0));
                    _glyphs.Add(chr, glyph);
                    _characters.Add(chr);
                }
            }

            using (Stream str = typeof(TestFont).Assembly.GetManifestResourceStream("QuikTestApplication.font.dat"))
            {
                TextureData = new byte[(int)str.Length];
                str.Read(TextureData, 0, (int)str.Length);
            }
            
            // Evil pointer stuff. Beware!
            Span<uint> head = MemoryMarshal.Cast<byte, uint>(TextureData);
            for (int i = 0; i < head.Length; i++)
            {
                if (head[i] == 0xff000000)
                {
                    head[i] = 0x00000000;
                }
            }
        }

        public override bool HasCharacter(int character)
        {
            return _characters.Contains((char) character);
        }

        public override void GetCharacter(int character, out QuikTexture texture, out QuikGlyph glyph)
        {
            if (!_glyphs.TryGetValue(character, out glyph))
            {
                glyph = _glyphs['?'];
            }

            texture = Texture;
        }
    }
}