namespace G
{
    [Generator(LanguageNames.CSharp)]
    public class OperatorsGenerator : IIncrementalGenerator
    {
        private const string AttributeSource = @"// <auto-generated />
using System;

namespace QWERTYkez.Mensura
{
    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
    internal sealed class OperatorsGeneratorAttribute : Attribute
    {
        public string CoeffName { get; }

        public OperatorsGeneratorAttribute()
        {
        }

        public OperatorsGeneratorAttribute(string coeffName)
        {
            CoeffName = coeffName;
        }
    }
}";

        public void Initialize(IncrementalGeneratorInitializationContext context)
        {
            // 1. Внедряем атрибут
            context.RegisterPostInitializationOutput(static postInitializationContext =>
            {
                postInitializationContext.AddSource(
                    ".OperatorsGeneratorAttribute.g.cs",
                    SourceText.From(AttributeSource, Encoding.UTF8));
            });

            // 2. Ищем методы-операторы, помеченные атрибутом
            IncrementalValuesProvider<OperatorInfo> operatorDeclarations = context.SyntaxProvider
                .ForAttributeWithMetadataName(
                    fullyQualifiedMetadataName: "QWERTYkez.Mensura.OperatorsGeneratorAttribute",
                    predicate: static (node, _) => node is OperatorDeclarationSyntax,
                    transform: static (ctx, _) => GetSemanticTargetForGeneration(ctx))
                .Where(static m => m is not null)!;

            // 3. Выполняем генерацию кода
            context.RegisterSourceOutput(operatorDeclarations, static (spc, opInfo) => Execute(spc, opInfo));
        }

        private static OperatorInfo GetSemanticTargetForGeneration(GeneratorAttributeSyntaxContext context)
        {
            var opDeclaration = (OperatorDeclarationSyntax)context.TargetNode;

            if (opDeclaration.ParameterList.Parameters.Count < 2) return null;

            if (context.SemanticModel.GetDeclaredSymbol(opDeclaration) is not IMethodSymbol symbol) return null;

            var namespaceName = symbol.ContainingNamespace.ToDisplayString();

            var leftType = opDeclaration.ParameterList.Parameters[0].Type?.ToString() ?? "";
            var rightType = opDeclaration.ParameterList.Parameters[1].Type?.ToString() ?? "";
            var returnType = opDeclaration.ReturnType.ToString();

            var isMultiplication = opDeclaration.OperatorToken.IsKind(SyntaxKind.AsteriskToken);
            var isDivision = opDeclaration.OperatorToken.IsKind(SyntaxKind.SlashToken);

            if (!isMultiplication && !isDivision) return null;

            // АВТОМАТИЧЕСКИЙ ПОИСК: Ищем содержащий тип (структуру/рекорд) по синтаксическому дереву
            string containingTypeName = leftType; // Фолбэк по умолчанию
            var parentTypeDeclaration = opDeclaration.Ancestors()
                .OfType<TypeDeclarationSyntax>()
                .FirstOrDefault();

            if (parentTypeDeclaration != null)
            {
                containingTypeName = parentTypeDeclaration.Identifier.ToString();
            }

            string coeffName = null;
            string coeffType = containingTypeName; // По умолчанию считаем, что коэффициент в текущем классе

            // Извлекаем аргумент атрибута
            var attribute = opDeclaration.AttributeLists
                .SelectMany(al => al.Attributes)
                .FirstOrDefault(a => a.Name.ToString().EndsWith("OperatorsGenerator") || a.Name.ToString() == "OperatorsGenerator");

            if (attribute?.ArgumentList != null && attribute.ArgumentList.Arguments.Count > 0)
            {
                var expr = attribute.ArgumentList.Arguments[0].Expression;

                // Проверяем синтаксис nameof(...)
                if (expr is InvocationExpressionSyntax invocation &&
                    invocation.Expression.ToString() == "nameof" &&
                    invocation.ArgumentList.Arguments.Count > 0)
                {
                    var nameofArg = invocation.ArgumentList.Arguments[0].Expression;

                    // Если все-таки написали явно nameof(Type.Property)
                    if (nameofArg is MemberAccessExpressionSyntax memberAccess)
                    {
                        coeffType = memberAccess.Expression.ToString();
                        coeffName = memberAccess.Name.ToString();
                    }
                    else
                    {
                        coeffName = nameofArg.ToString();
                        // coeffType остается равным содержащему классу containingTypeName
                    }
                }
                else
                {
                    coeffName = expr.ToString().Trim('"');
                    // coeffType остается равным содержащему классу containingTypeName
                }
            }

            return new OperatorInfo
            {
                Namespace = namespaceName,
                LeftType = leftType,
                RightType = rightType,
                ReturnType = returnType,
                IsMultiplication = isMultiplication,
                IsDivision = isDivision,
                CoeffName = coeffName,
                CoeffType = coeffType,
                HasCoeff = !string.IsNullOrWhiteSpace(coeffName)
            };
        }

        private static void Execute(SourceProductionContext context, OperatorInfo info)
        {
            var opType = info.IsMultiplication ? "Mul" : "Div";
            var coeffSuffix = info.HasCoeff ? ".Coeff" : "";
            var hintName = $"Op.{info.LeftType}.{opType}.{info.RightType}{coeffSuffix}.g.cs";

            var source = info.IsMultiplication
                ? GenerateMultiplicationSource(info)
                : GenerateDivisionSource(info);

            context.AddSource(hintName, SourceText.From(source, Encoding.UTF8));
        }

        private static string GenerateMultiplicationSource(OperatorInfo info)
        {
            return $@"// <auto-generated />
using System;
using System.Collections.Generic;

namespace {info.Namespace};

public readonly partial record struct {info.LeftType}
{{
    public static {info.ReturnType}[] operator *({info.LeftType} left, {info.RightType}[] right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * left._Value)" : "left._Value")}.Mul<{info.RightType}, {info.ReturnType}>(right);
    public static List<{info.ReturnType}> operator *({info.LeftType} left, List<{info.RightType}> right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * left._Value)" : "left._Value")}.Mul<{info.RightType}, {info.ReturnType}>(right);
    public static IEnumerable<{info.ReturnType}> operator *({info.LeftType} left, IEnumerable<{info.RightType}> right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * left._Value)" : "left._Value")}.Mul<{info.RightType}, {info.ReturnType}>(right);
}}

public readonly partial record struct {info.RightType}
{{
    public static {info.ReturnType}[] operator *({info.LeftType}[] left, {info.RightType} right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * right._Value)" : "right._Value")}.Mul<{info.LeftType}, {info.ReturnType}>(left);
    public static List<{info.ReturnType}> operator *(List<{info.LeftType}> left, {info.RightType} right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * right._Value)" : "right._Value")}.Mul<{info.LeftType}, {info.ReturnType}>(left);
    public static IEnumerable<{info.ReturnType}> operator *(IEnumerable<{info.LeftType}> left, {info.RightType} right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * right._Value)" : "right._Value")}.Mul<{info.LeftType}, {info.ReturnType}>(left);
}}";
        }

        private static string GenerateDivisionSource(OperatorInfo info)
        {
            return $@"// <auto-generated />
using System;
using System.Collections.Generic;

namespace {info.Namespace};

public readonly partial record struct {info.LeftType}
{{
    public static {info.ReturnType}[] operator /({info.LeftType} left, {info.RightType}[] right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * left._Value)" : "left._Value")}.Div<{info.RightType}, {info.ReturnType}>(right);
    public static List<{info.ReturnType}> operator /({info.LeftType} left, List<{info.RightType}> right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * left._Value)" : "left._Value")}.Div<{info.RightType}, {info.ReturnType}>(right);
    public static IEnumerable<{info.ReturnType}> operator /({info.LeftType} left, IEnumerable<{info.RightType}> right) => {(info.HasCoeff ? $"({info.CoeffType}.{info.CoeffName} * left._Value)" : "left._Value")}.Div<{info.RightType}, {info.ReturnType}>(right);
}}

public readonly partial record struct {info.RightType}
{{
    public static {info.ReturnType}[] operator /({info.LeftType}[] left, {info.RightType} right) => {(info.HasCoeff ? $"left.Mul<{info.LeftType}, {info.ReturnType}>({info.CoeffType}.{info.CoeffName} / right._Value)" : $"left.Div<{info.LeftType}, {info.ReturnType}>(right._Value)")};
    public static List<{info.ReturnType}> operator /(List<{info.LeftType}> left, {info.RightType} right) => {(info.HasCoeff ? $"left.Mul<{info.LeftType}, {info.ReturnType}>({info.CoeffType}.{info.CoeffName} / right._Value)" : $"left.Div<{info.LeftType}, {info.ReturnType}>(right._Value)")};
    public static IEnumerable<{info.ReturnType}> operator /(IEnumerable<{info.LeftType}> left, {info.RightType} right) => {(info.HasCoeff ? $"left.Mul<{info.LeftType}, {info.ReturnType}>({info.CoeffType}.{info.CoeffName} / right._Value)" : $"left.Div<{info.LeftType}, {info.ReturnType}>(right._Value)")};
}}";
        }
        
        private class OperatorInfo
        {
            public string Namespace { get; set; } = string.Empty;
            public string LeftType { get; set; } = string.Empty;
            public string RightType { get; set; } = string.Empty;
            public string ReturnType { get; set; } = string.Empty;
            public bool IsMultiplication { get; set; }
            public bool IsDivision { get; set; }
            public string CoeffName { get; set; }
            public string CoeffType { get; set; }
            public bool HasCoeff { get; set; } }
    }
}