//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="Generator"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//     
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//     
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;

namespace GenerateGL.CodeGen
{
    internal sealed class Generator
    {

        private static readonly string[] TargetVersions = {
            "3.3", "4.0", "4.1", "4.2", "4.3", "4.4", "4.5", "4.6"
        };

        private readonly IReadOnlyDictionary<string, GlCommand> _commands;
        private readonly IReadOnlyList<GlFeature> _features;
        private readonly string _outputRoot;

        public Generator(
               IReadOnlyDictionary<string, GlCommand> commands,
               IReadOnlyList<GlFeature> features,
               string outputRoot
        )
        {
            _commands = commands;
            _features = features;
            _outputRoot = outputRoot;
        }

        public void Run()
        {
            if (Directory.Exists(_outputRoot)) {
                Directory.Delete(_outputRoot, recursive:true);
            }
            Directory.CreateDirectory(_outputRoot);
            List<GlCommand> all = new List<GlCommand>();
            foreach (string v in TargetVersions)
            {
                IReadOnlyList<GlCommand> cmds = CollectCommandsUpToVersion(v);
                all.AddRange(cmds);
                WriteOpenGLFunctionFile(v, cmds);
                WriteGlContextFile(v, cmds);
            }
            WriteMergedGlContextFile(all);
        }

        private IReadOnlyList<GlCommand> CollectCommandsUpToVersion(
                                         string version
        )
        {
            Version target = Version.Parse(version);
            IEnumerable<GlCommand?> selected = _features.Where(f => Version.TryParse(f.Version, out Version? fv) &&
                                                                    fv <= target)
                                                        .SelectMany(f => f.RequiresCommands)
                                                        .Distinct(StringComparer.Ordinal)
                                                        .Select(name => _commands.TryGetValue(name, out GlCommand? c) ?
                                                                        c :
                                                                        null)
                                                        .Where(c => c != null)!;
            return selected.ToList()!;
        }

        private static string DelegateSignature(
                              string ret,
                              IReadOnlyList<string> paramTypes
        )
        {
            if (paramTypes.Count == 0) {
                return $"delegate*<{ret}>";
            }
            return $"delegate*<{string.Join(", ", paramTypes)}, {ret}>";
        }

        private static string SafeName(
                              string name
        )
        {
            return string.IsNullOrWhiteSpace(name) ?
                   "arg" :
                   name switch
            {
                "params" => "@params",
                "event" => "@event",
                _ => name
            };
        }

        private static bool ShouldSkip(
                            string name
        )
        {
            // No skipping; include legacy/fixed-function APIs as well.
            return false;
        }

        private static string TrimGlPrefix(
                              string name
        )
        {
            if (name.StartsWith("gl", StringComparison.Ordinal) && name.Length > 2) {
                return name.Substring(2);
            }
            return name;
        }

        private void WriteGlContextFile(
                     string version,
                     IReadOnlyList<GlCommand> commands
        )
        {
            StringBuilder sb = new StringBuilder();
            sb.AppendLine("// <auto-generated>");
            sb.AppendLine($"// Generated by StgSharp.GenerateGL on {DateTime.UtcNow.ToString("u", CultureInfo.InvariantCulture)}");
            sb.AppendLine($"// Version: {version}");
            sb.AppendLine("// </auto-generated>");
            sb.AppendLine("using System;\nusing System.Runtime.CompilerServices;\n");
            sb.AppendLine("namespace StgSharp.Graphics.OpenGL");
            sb.AppendLine("{");
            sb.AppendLine("    public unsafe partial struct OpenglContext");
            sb.AppendLine("    {");
            foreach (GlCommand cmd in commands.OrderBy(c => c!.Name, StringComparer.Ordinal))
            {
                string ret = CsTypeMapper.MapDelegateReturn(cmd.ReturnType);
                List<string> paramTypes = new List<string>();
                foreach (GlParam p in cmd.Parameters)
                {
                    string mapped = CsTypeMapper.MapDelegateParameter(p);
                    paramTypes.Add(mapped);
                }
                string decl = DelegateSignature(ret, paramTypes);
                sb.AppendLine($"        internal unsafe {decl} {cmd.Name};");
            }
            sb.AppendLine("    }");
            sb.AppendLine("}");

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

        private void WriteMergedGlContextFile(
                     IReadOnlyList<GlCommand> commands
        )
        {
            List<GlCommand> distinct = commands.Where(c => !ShouldSkip(c.Name))
                                               .GroupBy(c => c.Name, StringComparer.Ordinal)
                                               .Select(g => g.First())
                                               .OrderBy(c => c.Name, StringComparer.Ordinal)
                                               .ToList();

            StringBuilder sb = new StringBuilder();
            sb.AppendLine("// <auto-generated>");
            sb.AppendLine($"// Generated by StgSharp.GenerateGL on {DateTime.UtcNow.ToString("u", CultureInfo.InvariantCulture)}");
            sb.AppendLine("// Aggregated GL3+ commands");
            sb.AppendLine("// </auto-generated>");
            sb.AppendLine("using System;\nusing System.Runtime.CompilerServices;\n");
            sb.AppendLine("namespace StgSharp.Graphics.OpenGL");
            sb.AppendLine("{");
            sb.AppendLine("    public unsafe partial struct OpenglContext");
            sb.AppendLine("    {");
            foreach (GlCommand cmd in distinct)
            {
                string ret = CsTypeMapper.MapDelegateReturn(cmd.ReturnType);
                List<string> paramTypes = new List<string>();
                foreach (GlParam p in cmd.Parameters)
                {
                    string mapped = CsTypeMapper.MapDelegateParameter(p);
                    paramTypes.Add(mapped);
                }
                string decl = DelegateSignature(ret, paramTypes);
                sb.AppendLine($"        internal unsafe {decl} {cmd.Name};");
            }
            sb.AppendLine("    }");
            sb.AppendLine("}");

            string fileName = Path.Combine(_outputRoot, "glContext.cs");
            File.WriteAllText(fileName, sb.ToString(), Encoding.UTF8);
        }

        private void WriteOpenGLFunctionFile(
                     string version,
                     IReadOnlyList<GlCommand> commands
        )
        {
            StringBuilder sb = new StringBuilder();
            sb.AppendLine("// <auto-generated>");
            sb.AppendLine($"// Generated by StgSharp.GenerateGL on {DateTime.UtcNow.ToString("u", CultureInfo.InvariantCulture)}");
            sb.AppendLine($"// Version: {version}");
            sb.AppendLine("// </auto-generated>");
            sb.AppendLine("using System;\nusing System.Runtime.CompilerServices;\nusing StgSharp.Graphics.OpenGL;\n");
            sb.AppendLine("namespace StgSharp.Graphics.OpenGL");
            sb.AppendLine("{");
            sb.AppendLine("    public unsafe partial class OpenGLFunction");
            sb.AppendLine("    {");
            foreach (GlCommand cmd in commands.OrderBy(c => c!.Name, StringComparer.Ordinal))
            {
                string ret = CsTypeMapper.MapReturn(cmd.ReturnType);
                string rawName = cmd.Name; // original glXxx
                string methodName = TrimGlPrefix(rawName);
                List<string> paramList = new List<string>();
                List<string> callArgs = new List<string>();
                foreach (GlParam p in cmd.Parameters)
                {
                    string mapped = CsTypeMapper.MapParameter(p);
                    string pname = SafeName(p.Name);
                    paramList.Add($"{mapped} {pname}");
                    if (mapped == "GlHandle")
                    {
                        callArgs.Add($"{pname}.Value");
                    } else
                    {
                        callArgs.Add(pname);
                    }
                }
                string signature = string.Join(", ", paramList);
                string call = string.Join(", ", callArgs);
                sb.AppendLine($"        [MethodImpl(MethodImplOptions.AggressiveInlining)]");
                sb.AppendLine($"        public {ret} {methodName}({signature})");
                sb.AppendLine("        {");
                string prefix = ret == "void" ? string.Empty : "return ";
                sb.AppendLine($"            {prefix}Context.{rawName}({call});");
                sb.AppendLine("        }");
                sb.AppendLine();
            }
            sb.AppendLine("    }");
            sb.AppendLine("}");

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

    }
}