using System.Linq;
using System.Text;
using GFramework.SourceGenerators.Common.diagnostics;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace GFramework.SourceGenerators.rule;

[Generator]
public sealed class ContextAwareGenerator : IIncrementalGenerator
{
    private const string AttributeMetadataName =
        "GFramework.SourceGenerators.Attributes.rule.ContextAwareAttribute";

    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        // 1️⃣ 查找候选类
        var candidates = context.SyntaxProvider
            .CreateSyntaxProvider(
                predicate: static (node, _) => node is ClassDeclarationSyntax,
                transform: static (ctx, _) => GetCandidate(ctx)
            )
            .Where(static s => s is not null);

        // 2️⃣ 注册生成输出
        context.RegisterSourceOutput(candidates, static (spc, symbol) =>
        {
            if (symbol != null)
                GenerateOutput(spc, symbol);
        });
    }

    #region 候选类查找

    private static INamedTypeSymbol? GetCandidate(GeneratorSyntaxContext context)
    {
        if (context.SemanticModel.GetDeclaredSymbol(context.Node) is not INamedTypeSymbol symbol)
            return null;

        // 仅筛选带有 ContextAwareAttribute 的类
        var hasAttr = symbol.GetAttributes()
            .Any(attr => attr.AttributeClass?.ToDisplayString() == AttributeMetadataName);

        return hasAttr ? symbol : null;
    }

    #endregion

    #region 输出生成 + 诊断

    private static void GenerateOutput(SourceProductionContext context, INamedTypeSymbol symbol)
    {
        var syntax = symbol.DeclaringSyntaxReferences.FirstOrDefault()?.GetSyntax() as ClassDeclarationSyntax;
        if (syntax == null)
            return;

        // 1️⃣ 必须是 partial
        if (!syntax.Modifiers.Any(SyntaxKind.PartialKeyword))
        {
            context.ReportDiagnostic(Diagnostic.Create(
                CommonDiagnostics.ClassMustBePartial,
                syntax.Identifier.GetLocation(),
                symbol.Name
            ));
            return;
        }

        // 2️⃣ 必须实现 IContextAware（直接或间接）
        if (!symbol.AllInterfaces.Any(i => i.ToDisplayString() == "GFramework.Core.rule.IContextAware"))
        {
            context.ReportDiagnostic(Diagnostic.Create(
                ContextAwareDiagnostic.ClassMustImplementIContextAware,
                syntax.Identifier.GetLocation(),
                symbol.Name
            ));
            return;
        }

        // 3️⃣ 生成源码
        var ns = symbol.ContainingNamespace.IsGlobalNamespace
            ? null
            : symbol.ContainingNamespace.ToDisplayString();

        var source = GenerateSource(ns, symbol);
        context
            .AddSource(
                $"{symbol.Name}.ContextAware.g.cs",
                source);
    }

    #endregion

    #region 源码生成

    private static string GenerateSource(string? ns, INamedTypeSymbol symbol)
    {
        var sb = new StringBuilder();
        sb.AppendLine("// <auto-generated/>");
        sb.AppendLine("#nullable enable");

        if (ns is not null)
        {
            sb.AppendLine($"namespace {ns};");
            sb.AppendLine();
        }

        sb.AppendLine($"partial class {symbol.Name}");
        sb.AppendLine("{");
        sb.AppendLine(
            "    protected GFramework.Core.architecture.IArchitectureContext Context { get; private set; } = null!;");
        sb.AppendLine();
        sb.AppendLine("    void GFramework.Core.rule.IContextAware.SetContext(");
        sb.AppendLine("        GFramework.Core.architecture.IArchitectureContext context)");
        sb.AppendLine("    {");
        sb.AppendLine("        Context = context;");
        sb.AppendLine("    }");
        sb.AppendLine("}");

        return sb.ToString().TrimEnd();
    }

    #endregion
}