using System.Reflection;
using System.Runtime.InteropServices;
using BlurgText;
using Dashboard.Drawing.OpenGL.Text;
using OpenTK.Graphics.OpenGL;
using OpenTK.Mathematics;

namespace Dashboard.Drawing.OpenGL.Executors
{
    public class TextCommandExecutor : ICommandExecutor, IInitializer
    {
        public IEnumerable<string> Extensions { get; } = new[] { "DB_Text" };
        public IContextExecutor Executor { get; private set; }
        private BlurgEngine Engine => Executor.ResourcePool.GetResourceManager<BlurgEngine>();
        public bool IsInitialized { get; private set; }

        private DrawCallRecorder _recorder;
        private int _program = 0;
        private int _transformsLocation = -1;
        private int _atlasLocation = -1;
        private int _borderWidthLocation = -1;
        private int _borderColorLocation = -1;
        private int _fillColorLocation = -1;

        public TextCommandExecutor()
        {
            Executor = null!;
            _recorder = new DrawCallRecorder(this);
        }

        public void Initialize()
        {
            if (IsInitialized)
                return;
            IsInitialized = true;

            Assembly self = typeof(TextCommandExecutor).Assembly;

            using Stream vsource = self.GetManifestResourceStream("Dashboard.Drawing.OpenGL.Executors.text.vert")!;
            using Stream fsource = self.GetManifestResourceStream("Dashboard.Drawing.OpenGL.Executors.text.frag")!;
            int vs = ShaderUtil.CompileShader(ShaderType.VertexShader, vsource);
            int fs = ShaderUtil.CompileShader(ShaderType.FragmentShader, fsource);
            _program = ShaderUtil.LinkProgram(vs, fs, new []
            {
                "a_v3Position",
                "a_v2TexCoords",
            });
            GL.DeleteShader(vs);
            GL.DeleteShader(fs);

            _transformsLocation = GL.GetUniformLocation(_program, "m4Transforms");
            _atlasLocation = GL.GetUniformLocation(_program, "txAtlas");
            _borderWidthLocation = GL.GetUniformLocation(_program, "fBorderWidth");
            _borderColorLocation = GL.GetUniformLocation(_program, "v4BorderColor");
            _fillColorLocation = GL.GetUniformLocation(_program, "v4FillColor");

            _recorder.Initialize();
        }

        public void SetContextExecutor(IContextExecutor executor)
        {
            Executor = executor;
        }

        public void BeginFrame()
        {
        }

        public void BeginDraw()
        {
            _recorder.Clear();
        }

        public void EndDraw()
        {
            GL.UseProgram(_program);
            GL.Enable(EnableCap.Blend);
            GL.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.OneMinusSrcAlpha);
            _recorder.Execute();
            GL.Disable(EnableCap.Blend);
        }

        public void EndFrame()
        {
        }

        public void ProcessCommand(ICommandFrame frame)
        {
            switch (frame.Command.Name)
            {
                case "Text":
                    DrawText(frame);
                    break;
            }
        }

        private void DrawText(ICommandFrame frame)
        {
            TextCommandArgs args = frame.GetParameter<TextCommandArgs>();
            DbBlurgFont font = Engine.InternFont(args.Font);

            BlurgColor color;
            switch (args.TextBrush)
            {
            case SolidBrush solid:
                color = new BlurgColor()
                {
                    R = solid.Color.R,
                    G = solid.Color.G,
                    B = solid.Color.B,
                    A = solid.Color.A,
                };
                break;
            default:
                color = new BlurgColor() { R = 255, G = 0, B = 255, A = 255 };
                break;
            }

            BlurgResult? result = Engine.Blurg.BuildString(font.Font, font.Size, color, args.Text);

            if (result == null)
                return;

            Vector3 position = new Vector3(args.Position.X, args.Position.Y, args.Position.Z);
            ExecuteBlurgResult(result, position);

            result.Dispose();
        }

        private void ExecuteBlurgResult(BlurgResult result, Vector3 position)
        {
            Matrix4 transforms = Executor.TransformStack.Top;

            for (int i = 0; i < result.Count; i++)
            {
                BlurgRect rect = result[i];

                int texture = (int)rect.UserData;
                Vector4 color = new Vector4(rect.Color.R / 255f, rect.Color.G / 255f, rect.Color.B / 255f,
                    rect.Color.A / 255f);

                if (i == 0)
                {
                    _recorder.Begin(PrimitiveType.Triangles, new Call()
                    {
                        Texture = texture,
                        FillColor = color,
                        Transforms = transforms,
                    });
                }
                else if (
                    _recorder.CurrentCall.Texture != texture ||
                    _recorder.CurrentCall.FillColor != color)
                {
                    _recorder.End();
                    Call call = new Call()
                    {
                        Texture = texture,
                        FillColor = color,
                        Transforms = transforms,
                    };
                    _recorder.Begin(PrimitiveType.Triangles, call);
                }

                Vector3 p00 = new Vector3(rect.X, rect.Y, 0) + position;
                Vector3 p10 = p00 + new Vector3(rect.Width, 0, 0);
                Vector3 p11 = p00 + new Vector3(rect.Width, rect.Height, 0);
                Vector3 p01 = p00 + new Vector3(0, rect.Height, 0);

                Vector2 uv00 = new Vector2(rect.U0, rect.V0);
                Vector2 uv10 = new Vector2(rect.U1, rect.V0);
                Vector2 uv11 = new Vector2(rect.U1, rect.V1);
                Vector2 uv01 = new Vector2(rect.U0, rect.V1);

                _recorder.Vertex(p00, uv00);
                _recorder.Vertex(p10, uv10);
                _recorder.Vertex(p11, uv11);

                _recorder.Vertex(p00, uv00);
                _recorder.Vertex(p11, uv11);
                _recorder.Vertex(p01, uv01);
            }
            _recorder.End();
        }

        private struct Call
        {
            public Matrix4 Transforms = Matrix4.Identity;
            public int Texture = 0;
            public float BorderWidth = 0f;
            public Vector4 FillColor = Vector4.One;
            public Vector4 BorderColor = new Vector4(0,0,0,1);

            public Call()
            {
            }
        }

        [StructLayout(LayoutKind.Explicit, Size = 8 * sizeof(float))]
        private struct Vertex
        {
            [FieldOffset(0)]
            public Vector3 Position;
            [FieldOffset(4 * sizeof(float))]
            public Vector2 TexCoords;
        }

        private class DrawCallRecorder : DrawCallRecorder<Call, Vertex>
        {
            private TextCommandExecutor Executor { get; }

            public DrawCallRecorder(TextCommandExecutor executor)
            {
                Executor = executor;
            }

            public void Vertex(Vector3 position, Vector2 texCoords)
            {
                Vertex(new Vertex(){Position = position, TexCoords = texCoords});
            }

            protected override void PrepareCall(in Call call)
            {
                Matrix4 transforms = call.Transforms;
                GL.UniformMatrix4f(Executor._transformsLocation, 1, true, ref transforms);
                GL.Uniform1f(Executor._borderWidthLocation, call.BorderWidth);
                GL.Uniform4f(Executor._borderColorLocation, 1, in call.BorderColor);
                GL.Uniform4f(Executor._fillColorLocation, 1, in call.FillColor);
                GL.Uniform1i(Executor._atlasLocation, 0);
                GL.ActiveTexture(TextureUnit.Texture0);
                GL.BindTexture(TextureTarget.Texture2d, call.Texture);
            }

            protected override void SetVertexFormat()
            {
                GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, VertexSize, 0);
                GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, VertexSize, 4*sizeof(float));
                GL.EnableVertexAttribArray(0);
                GL.EnableVertexAttribArray(1);
            }
        }
    }
}