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

namespace GFramework.Godot.SourceGenerators.logging;

/// <summary>
/// 日志生成器，用于为标记了GodotLogAttribute的类自动生成日志字段
/// </summary>
[Generator]
public sealed class GodotLoggerGenerator : IIncrementalGenerator
{
    private const string AttributeMetadataName =
        $"{PathContests.GodotSourceGeneratorsAbstractionsPath}.logging.GodotLogAttribute";

    private const string AttributeShortNameWithoutSuffix = "GodotLog";

    /// <summary>
    /// 初始化源生成器，设置语法提供程序和源输出注册
    /// </summary>
    /// <param name="context">增量生成器初始化上下文</param>
    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        // 创建语法提供程序，用于查找标记了GodotLogAttribute的类声明
        var targets = context.SyntaxProvider
            .CreateSyntaxProvider(
                static (node, _) =>
                {
                    if (node is not ClassDeclarationSyntax cls) return false;
                    return cls.AttributeLists
                        .SelectMany(a => a.Attributes)
                        .Any(a => a.Name.ToString().Contains(AttributeShortNameWithoutSuffix));
                },
                static (ctx, _) =>
                {
                    var cls = (ClassDeclarationSyntax)ctx.Node;
                    var sym = ctx.SemanticModel.GetDeclaredSymbol(cls);
                    return (ClassDecl: cls, Symbol: sym);
                })
            .Where(x => x.Symbol is not null);

        // 注册源输出，为符合条件的类生成日志字段代码
        context.RegisterSourceOutput(targets, (spc, pair) =>
        {
            try
            {
                var classDecl = pair.ClassDecl;
                var classSymbol = pair.Symbol!;

                var attr = GetAttribute(classSymbol);
                if (attr is null) return;

                if (!classDecl.Modifiers.Any(SyntaxKind.PartialKeyword))
                {
                    spc.ReportDiagnostic(Diagnostic.Create(
                        CommonDiagnostics.ClassMustBePartial,
                        classDecl.Identifier.GetLocation(),
                        classSymbol.Name));
                    return;
                }

                var source = Generate(classSymbol, attr);
                spc.AddSource($"{classSymbol.Name}.Logger.g.cs", SourceText.From(source, Encoding.UTF8));
            }
            catch (Exception ex)
            {
                var safeName = pair.Symbol?.Name ?? "Unknown";
                var errorSource = $"// Source generator error: {ex.Message}\n// StackTrace:\n// {ex.StackTrace}";
                spc.AddSource($"{safeName}.Logger.Error.g.cs", SourceText.From(errorSource, Encoding.UTF8));
            }
        });
    }

    /// <summary>
    /// 获取类符号上的GodotLogAttribute属性数据
    /// </summary>
    /// <param name="classSymbol">类符号</param>
    /// <returns>GodotLogAttribute属性数据，如果未找到则返回null</returns>
    private static AttributeData? GetAttribute(INamedTypeSymbol classSymbol)
        => classSymbol.GetAttributes().FirstOrDefault(a =>
        {
            var cls = a.AttributeClass;
            return cls != null &&
                   (cls.ToDisplayString() == AttributeMetadataName ||
                    cls.Name.StartsWith(AttributeShortNameWithoutSuffix));
        });

    /// <summary>
    /// 生成日志字段的源代码
    /// </summary>
    /// <param name="classSymbol">类符号</param>
    /// <param name="attr">GodotLogAttribute属性数据</param>
    /// <returns>生成的源代码字符串</returns>
    private static string Generate(INamedTypeSymbol classSymbol, AttributeData attr)
    {
        var ns = classSymbol.ContainingNamespace.IsGlobalNamespace
            ? null
            : classSymbol.ContainingNamespace.ToDisplayString();
        var className = classSymbol.Name;

        // 解析构造函数参数
        var name = className;
        if (attr.ConstructorArguments.Length > 0 && attr.ConstructorArguments[0].Value is string s &&
            !string.IsNullOrWhiteSpace(s))
        {
            name = s;
        }

        // 解析命名参数
        var fieldName = GetNamedArg(attr, "FieldName")?.ToString() ?? "_log";
        var access = GetNamedArg(attr, "AccessModifier")?.ToString() ?? "private";
        var isStatic = GetNamedArg(attr, "IsStatic") is not bool b || b;
        var staticKeyword = isStatic ? "static " : "";

        var sb = new StringBuilder();
        sb.AppendLine("// <auto-generated />");
        sb.AppendLine($"using {PathContests.CoreAbstractionsNamespace}.logging;");
        sb.AppendLine($"using {PathContests.GodotNamespace}.logging;");
        sb.AppendLine();

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

        sb.AppendLine($"    public partial class {className}");
        sb.AppendLine("    {");
        sb.AppendLine("        /// <summary>Auto-generated logger</summary>");
        sb.AppendLine(
            $"        {access} {staticKeyword}readonly ILogger {fieldName} = new GodotLoggerFactory().GetLogger(\"{name}\");");
        sb.AppendLine("    }");

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

        return sb.ToString();
    }

    /// <summary>
    /// 从属性数据中获取指定名称的命名参数值
    /// </summary>
    /// <param name="attr">属性数据</param>
    /// <param name="name">参数名称</param>
    /// <returns>参数值，如果未找到则返回null</returns>
    private static object? GetNamedArg(AttributeData attr, string name)
        => attr.NamedArguments.FirstOrDefault(kv => kv.Key == name).Value.Value;
}