//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="UniformOverloadEmitter"
// Project: StgSharp
// Copyright (c) Nitload.
// SPDX-License-Identifier: MIT
// -----------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

#pragma warning disable CA1305

namespace GenerateGL.CodeGen
{
    internal static partial class UniformOverloadEmitter
    {

        public static bool IsValueCommand(
                           GlCommand command
        )
        {
            return ValueCommandRegex().IsMatch(command.Name);
        }

        public static bool IsSetterCommand(
                           GlCommand command
        )
        {
            return IsValueCommand(command) || MatrixCommandRegex().IsMatch(command.Name);
        }

        public static void Write(
                           string outputRoot,
                           string version,
                           IReadOnlyList<GlCommand> commands
        )
        {
            List<GlCommand> valueCommands = commands.Where(IsValueCommand)
                                                    .OrderBy(c => c.Name, StringComparer.Ordinal)
                                                    .ToList();
            List<GlCommand> matrixConvenienceCommands = commands
                .Where(c => Matrix4FloatCommandRegex().IsMatch(c.Name))
                .OrderBy(c => c.Name, StringComparer.Ordinal)
                .ToList();

            if (valueCommands.Count == 0 && matrixConvenienceCommands.Count == 0) {
                return;
            }

            StringBuilder sb = new();
            sb.AppendLine("// <auto-generated>");
            sb.AppendLine($"// Generated by StgSharp.GenerateGL on {DateTime.UtcNow.ToString("u", CultureInfo.InvariantCulture)}");
            sb.AppendLine($"// Uniform overloads introduced in OpenGL {version}");
            sb.AppendLine("// </auto-generated>");
            sb.AppendLine("using System;");
            sb.AppendLine("using System.Runtime.CompilerServices;");
            sb.AppendLine("using StgSharp.Mathematics.Graphics;");
            sb.AppendLine();
            sb.AppendLine("namespace StgSharp.Graphics.OpenGL");
            sb.AppendLine("{");
            sb.AppendLine("    public unsafe partial class OpenGLFunction");
            sb.AppendLine("    {");

            foreach (GlCommand command in valueCommands) {
                EmitValueOverload(sb, command);
            }
            foreach (GlCommand command in valueCommands.Where(IsFloatVectorCommand)) {
                EmitVectorConvenienceOverload(sb, command);
            }
            foreach (GlCommand command in matrixConvenienceCommands) {
                EmitMatrixConvenienceOverload(sb, command);
            }

            sb.AppendLine("    }");
            sb.AppendLine("}");

            string fileName = Path.Combine(
                outputRoot,
                $"OpenGLFunction.Uniform.v{version.Replace('.', '_')}.g.cs");
            File.WriteAllText(fileName, sb.ToString(), Encoding.UTF8);
        }

        private static void EmitValueOverload(
                            StringBuilder sb,
                            GlCommand command
        )
        {
            Match match = ValueCommandRegex().Match(command.Name);
            bool hasProgram = match.Groups[1].Success;
            int dimension = int.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
            string scalarType = MapScalarType(match.Groups[3].Value);
            bool isVector = match.Groups[4].Success;
            string uniformType = $"Uniform<{string.Join(", ", Enumerable.Repeat(scalarType, dimension))}>";

            sb.AppendLine("        [MethodImpl(MethodImplOptions.AggressiveInlining)]");
            if (isVector)
            {
                string programParameter = hasProgram ? "GlHandle program, " : string.Empty;
                sb.AppendLine($"        public void SetUniformValue({programParameter}{uniformType} uniform, ReadOnlySpan<{scalarType}> values)");
                sb.AppendLine("        {");
                sb.AppendLine("            ArgumentNullException.ThrowIfNull(uniform);");
                if (dimension > 1)
                {
                    sb.AppendLine($"            if ((values.Length % {dimension}) != 0) {{");
                    sb.AppendLine($"                throw new ArgumentException(\"Uniform data length must be divisible by {dimension}.\", nameof(values));");
                    sb.AppendLine("            }");
                }
                sb.AppendLine($"            fixed ({scalarType}* valuesPtr = values) {{");
                string count = dimension == 1 ? "values.Length" : $"values.Length / {dimension}";
                sb.AppendLine($"                Context.{command.Name}({BuildPrefixArguments(hasProgram)}{count}, valuesPtr);");
                sb.AppendLine("            }");
                sb.AppendLine("        }");
            } else
            {
                string programParameter = hasProgram ? "GlHandle program, " : string.Empty;
                string values = string.Join(", ", Enumerable.Range(0, dimension)
                                                              .Select(i => $"{scalarType} v{i}"));
                string valueArguments = string.Join(", ", Enumerable.Range(0, dimension)
                                                                     .Select(i => $"v{i}"));
                sb.AppendLine($"        public void SetUniformValue({programParameter}{uniformType} uniform, {values})");
                sb.AppendLine("        {");
                sb.AppendLine("            ArgumentNullException.ThrowIfNull(uniform);");
                sb.AppendLine($"            Context.{command.Name}({BuildPrefixArguments(hasProgram)}{valueArguments});");
                sb.AppendLine("        }");
            }
            sb.AppendLine();
        }

        private static void EmitVectorConvenienceOverload(
                            StringBuilder sb,
                            GlCommand command
        )
        {
            Match match = ValueCommandRegex().Match(command.Name);
            bool hasProgram = match.Groups[1].Success;
            int dimension = int.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
            if (dimension < 2) {
                return;
            }

            string vectorType = $"Vec{dimension}";
            string programParameter = hasProgram ? "GlHandle program, " : string.Empty;
            sb.AppendLine("        [MethodImpl(MethodImplOptions.AggressiveInlining)]");
            sb.AppendLine($"        public void SetUniformValue({programParameter}Uniform<{vectorType}> uniform, {vectorType} value)");
            sb.AppendLine("        {");
            sb.AppendLine("            ArgumentNullException.ThrowIfNull(uniform);");
            sb.AppendLine($"            Context.{command.Name}({BuildPrefixArguments(hasProgram)}1, (float*)&value);");
            sb.AppendLine("        }");
            sb.AppendLine();
        }

        private static void EmitMatrixConvenienceOverload(
                            StringBuilder sb,
                            GlCommand command
        )
        {
            bool hasProgram = command.Name.StartsWith("glProgram", StringComparison.Ordinal);
            string programParameter = hasProgram ? "GlHandle program, " : string.Empty;
            sb.AppendLine("        [MethodImpl(MethodImplOptions.AggressiveInlining)]");
            sb.AppendLine($"        public void SetUniformValue({programParameter}Uniform<GraphicsMatrix> uniform, GraphicsMatrix value, bool transpose = false)");
            sb.AppendLine("        {");
            sb.AppendLine("            ArgumentNullException.ThrowIfNull(uniform);");
            sb.AppendLine($"            Context.{command.Name}({BuildPrefixArguments(hasProgram)}1, transpose ? (byte)1 : (byte)0, (float*)&value);");
            sb.AppendLine("        }");
            sb.AppendLine();
        }

        private static string BuildPrefixArguments(
                              bool hasProgram
        )
        {
            return hasProgram
                ? "program.Value, uniform.id.SignedValue, "
                : "uniform.id.SignedValue, ";
        }

        private static bool IsFloatVectorCommand(
                            GlCommand command
        )
        {
            Match match = ValueCommandRegex().Match(command.Name);
            return match.Success && match.Groups[3].Value == "f" && match.Groups[4].Success;
        }

        private static string MapScalarType(
                              string suffix
        )
        {
            return suffix switch
            {
                "f" => "float",
                "d" => "double",
                "i" => "int",
                "ui" => "uint",
                _ => throw new InvalidOperationException($"Unsupported uniform suffix: {suffix}")
            };
        }

        [GeneratedRegex("^gl(Program)?Uniform([1-4])(ui|[fdi])(v)?$",
                        RegexOptions.CultureInvariant)]
        private static partial Regex ValueCommandRegex();

        [GeneratedRegex("^gl(?:Program)?UniformMatrix4fv$", RegexOptions.CultureInvariant)]
        private static partial Regex Matrix4FloatCommandRegex();

        [GeneratedRegex("^gl(?:Program)?UniformMatrix[234](?:x[234])?[fd]v$",
                        RegexOptions.CultureInvariant)]
        private static partial Regex MatrixCommandRegex();

    }
}

#pragma warning restore CA1305