using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace Polonium.Generators.Generators;
[Generator]
public class PoloniumFactoryGenerator : AssetProcessGenerator
{
    public override void Execute(GeneratorExecutionContext context)
    {
        if (!(context.SyntaxReceiver is ClassSyntaxReceiver receiver))
            return;
        StringBuilder sb = new();
        sb
            .AppendLine("using System;")
            .AppendLine("using Polonium.Attributes;")
            .AppendLine("using Polonium.Interfaces;")
            .AppendLine("using Polonium.Resources;")
            .AppendLine("using Polonium.MessageManager;")
            .AppendLine("[AutoRegister]")
            .AppendLine("public class PoloniumFactoryRegister")
            .AppendLine("{")
            .AppendLine("    public static void Register()")
            .AppendLine("    {")
            .AppendLine("        GlobalRegistry.PoloniumFactory = new PoloniumFactory();")
            .AppendLine("    }")
            .AppendLine("    public class PoloniumFactory : IPoloniumFactory")
            .AppendLine("    {")
            .AppendLine("        public MessageHeader CreateMessageHeader()")
            .AppendLine("        {");
        Compilation compilation = context.Compilation;
        INamedTypeSymbol? signalHeader = compilation.GetTypeByMetadataName("Polonium.MessageManager.MessageHeader");
        
        bool founded = false;
        foreach (ClassDeclarationSyntax cls in receiver.Classes)
        {
            SemanticModel semanticModel = compilation.GetSemanticModel(cls.SyntaxTree);
            INamedTypeSymbol? nCls = semanticModel.GetDeclaredSymbol(cls) as INamedTypeSymbol;
            if(nCls is null)
                continue;
            if (IsDerivedFrom(nCls, signalHeader) && !nCls.IsAbstract)
            {
                sb.AppendLine($"            return new {nCls.ToDisplayString()}();");
                founded = true;
                break;
            }
        }
        if (!founded)
            sb.AppendLine($"            throw new NotImplementedException();");

        sb
            .AppendLine("        }")
            .AppendLine("    }")
            .AppendLine("}");
        
        context.AddSource("PoloniumFactoryRegistry.g.cs", sb.ToString());
    }
}