using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace LANCommander.SDK.SourceGenerators;

[Generator]
public class CmdletRegistrationGenerator : IIncrementalGenerator
{
    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        var cmdletClasses = context.SyntaxProvider
            .ForAttributeWithMetadataName(
                "System.Management.Automation.CmdletAttribute",
                predicate: static (node, _) => node is ClassDeclarationSyntax,
                transform: static (ctx, _) => GetCmdletInfo(ctx))
            .Where(static info => info is not null)
            .Select(static (info, _) => info!.Value);

        context.RegisterSourceOutput(
            cmdletClasses.Collect(),
            static (spc, cmdlets) => Execute(spc, cmdlets));
    }

    private static CmdletInfo? GetCmdletInfo(GeneratorAttributeSyntaxContext context)
    {
        var typeSymbol = (INamedTypeSymbol)context.TargetSymbol;

        foreach (var attr in typeSymbol.GetAttributes())
        {
            if (attr.AttributeClass?.ToDisplayString() != "System.Management.Automation.CmdletAttribute")
                continue;

            if (attr.ConstructorArguments.Length < 2)
                continue;

            var verb = attr.ConstructorArguments[0].Value?.ToString();
            var noun = attr.ConstructorArguments[1].Value?.ToString();

            if (verb is null || noun is null)
                continue;

            return new CmdletInfo
            {
                CmdletName = $"{verb}-{noun}",
                FullTypeName = typeSymbol.ToDisplayString()
            };
        }

        return null;
    }

    private static void Execute(SourceProductionContext context, ImmutableArray<CmdletInfo> cmdlets)
    {
        if (cmdlets.IsDefaultOrEmpty)
            return;

        var sorted = cmdlets.OrderBy(c => c.CmdletName).ToList();

        var sb = new StringBuilder();
        sb.AppendLine("// <auto-generated/>");
        sb.AppendLine("using System.Management.Automation.Runspaces;");
        sb.AppendLine();
        sb.AppendLine("namespace LANCommander.SDK.PowerShell.Extensions;");
        sb.AppendLine();
        sb.AppendLine("public static class InitialSessionStateExtensions");
        sb.AppendLine("{");
        sb.AppendLine("    public static void AddCustomCmdlets(this InitialSessionState initialSessionState)");
        sb.AppendLine("    {");

        foreach (var cmdlet in sorted)
        {
            sb.AppendLine($"        initialSessionState.Commands.Add(new SessionStateCmdletEntry(\"{cmdlet.CmdletName}\", typeof({cmdlet.FullTypeName}), null));");
        }

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

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

    private struct CmdletInfo
    {
        public string CmdletName;
        public string FullTypeName;
    }
}