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

namespace G;

[Generator(LanguageNames.CSharp)]
public class CollectionsOperatorsGenerator : IIncrementalGenerator
{
    private const string AttributeShortName = "CollectionsOperatorsGenerator";
    private const string AttributeFullName = AttributeShortName + "Attribute";

    private const string AttributeSource = @"namespace QWERTYkez.Mensura;

[System.AttributeUsage(System.AttributeTargets.Struct | System.AttributeTargets.Method, AllowMultiple = false, Inherited = false)]
internal sealed class CollectionsOperatorsGeneratorAttribute : System.Attribute { }";

    // Какие типы коллекций поддерживаем
    private static readonly (string Type, string Selector)[] CollectionTypes =
    [
        ("T[]", "array => array.Select(u => left * u).ToArray()"), // но нужно адаптировать под конкретный тип
        // Проще генерировать отдельные методы для каждого типа
    ];

    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        context.RegisterPostInitializationOutput(ctx =>
            ctx.AddSource($"{AttributeFullName}.g", SourceText.From(AttributeSource, Encoding.UTF8)));

        var operatorsPipeline = context.SyntaxProvider
            .CreateSyntaxProvider(
                predicate: static (node, _) => IsTargetType(node),
                transform: static (ctx, _) => GetTypeInfo(ctx))
            .Where(info => info.HasValue) // использование nullable value type
            .Select((info, _) => info!.Value)
            .Collect();

        context.RegisterSourceOutput(operatorsPipeline, GenerateOperators);
    }

    private static bool IsTargetType(SyntaxNode node)
    {
        if (node is not TypeDeclarationSyntax typeDecl)
            return false;

        // Должен быть partial и не generic
        if (!typeDecl.Modifiers.Any(SyntaxKind.PartialKeyword))
            return false;
        if (typeDecl.TypeParameterList != null)
            return false;

        // Проверяем наличие атрибута на самом типе
        foreach (var attrList in typeDecl.AttributeLists)
            foreach (var attr in attrList.Attributes)
            {
                string name = attr.Name.ToString();
                if (name == AttributeShortName || name == AttributeFullName)
                    return true;
            }

        // Или на операторах внутри
        foreach (var member in typeDecl.Members)
        {
            if (member is OperatorDeclarationSyntax opDecl &&
                opDecl.AttributeLists.SelectMany(al => al.Attributes)
                    .Any(a => a.Name.ToString().Contains(AttributeShortName)))
                return true;
        }
        return false;
    }

    private static TypeInfoData? GetTypeInfo(GeneratorSyntaxContext ctx)
    {
        var typeDecl = (TypeDeclarationSyntax)ctx.Node;
        var semanticModel = ctx.SemanticModel;

        var symbol = semanticModel.GetDeclaredSymbol(typeDecl);
        if (symbol == null) return null;

        string namespaceName = symbol.ContainingNamespace?.ToString() ?? "";

        // Формируем заголовок (для отладочных целей)
        var headerBuilder = new StringBuilder();
        foreach (var modifier in typeDecl.Modifiers)
            headerBuilder.Append(modifier.Text).Append(' ');
        if (typeDecl is RecordDeclarationSyntax)
            headerBuilder.Append("record ");
        headerBuilder.Append(typeDecl.Identifier.Text);
        string header = headerBuilder.ToString();

        // Собираем операторы
        var operators = ImmutableArray.CreateBuilder<Operation>();
        foreach (var member in typeDecl.Members)
        {
            if (member is not OperatorDeclarationSyntax opDecl) continue;
            if (opDecl.ParameterList.Parameters.Count != 2) continue;
            if (!opDecl.AttributeLists.SelectMany(al => al.Attributes)
                    .Any(a => a.Name.ToString().Contains(AttributeShortName))) continue;

            operators.Add(new Operation(
                opDecl.OperatorToken.Text,
                opDecl.ParameterList.Parameters[0].Type!.ToString(),
                opDecl.ParameterList.Parameters[1].Type!.ToString(),
                opDecl.ReturnType.ToString()
            ));
        }

        if (operators.Count == 0) return null;

        return new TypeInfoData(namespaceName, typeDecl.Identifier.Text, header, operators.ToImmutable());
    }

    private static void GenerateOperators(SourceProductionContext context, ImmutableArray<TypeInfoData> types)
    {
        foreach (var group in types.GroupBy(t => t.Namespace))
        {
            var document = new StringBuilder();
            document.AppendLine("namespace ").Append(group.Key).AppendLine(";");
            document.AppendLine("using System.Collections.Generic;");
            document.AppendLine("using System.Linq;");

            var allOperators = group.SelectMany(t => t.Operators).ToList();
            var multiplications = allOperators.Where(op => op.OperatorToken == "*").ToList();
            var divisions = allOperators.Where(op => op.OperatorToken == "/").ToList();

            // Генерация для умножения: left * collection и collection * left
            foreach (var mul in multiplications)
            {
                // left * collection
                document.AppendLine($@"
    public static {mul.ReturnType}[] operator *({mul.TypeA} left, {mul.TypeB}[] right) =>
        right.Select(u => left * u).ToArray();
    public static List<{mul.ReturnType}> operator *({mul.TypeA} left, List<{mul.TypeB}> right) =>
        right.Select(u => left * u).ToList();
    public static IEnumerable<{mul.ReturnType}> operator *({mul.TypeA} left, IEnumerable<{mul.TypeB}> right) =>
        right.Select(u => left * u);
");
                // collection * left
                document.AppendLine($@"
    public static {mul.ReturnType}[] operator *({mul.TypeB}[] left, {mul.TypeA} right) =>
        left.Select(u => u * right).ToArray();
    public static List<{mul.ReturnType}> operator *(List<{mul.TypeB}> left, {mul.TypeA} right) =>
        left.Select(u => u * right).ToList();
    public static IEnumerable<{mul.ReturnType}> operator *(IEnumerable<{mul.TypeB}> left, {mul.TypeA} right) =>
        left.Select(u => u * right);
");
            }

            // Деление: left / collection (left - тип A, collection - тип B)
            foreach (var div in divisions.Where(op => op.TypeA != null)) // все деления
            {
                // left / collection
                document.AppendLine($@"
    public static {div.ReturnType}[] operator /({div.TypeA} left, {div.TypeB}[] right) =>
        right.Select(u => left / u).ToArray();
    public static List<{div.ReturnType}> operator /({div.TypeA} left, List<{div.TypeB}> right) =>
        right.Select(u => left / u).ToList();
    public static IEnumerable<{div.ReturnType}> operator /({div.TypeA} left, IEnumerable<{div.TypeB}> right) =>
        right.Select(u => left / u);
");
                // collection / right (где right - тип B)
                document.AppendLine($@"
    public static {div.ReturnType}[] operator /({div.TypeA}[] left, {div.TypeB} right) =>
        left.Select(u => u / right).ToArray();
    public static List<{div.ReturnType}> operator /(List<{div.TypeA}> left, {div.TypeB} right) =>
        left.Select(u => u / right).ToList();
    public static IEnumerable<{div.ReturnType}> operator /(IEnumerable<{div.TypeA}> left, {div.TypeB} right) =>
        left.Select(u => u / right);
");
            }

            context.AddSource($"operations.{group.Key}.g", document.ToString());
        }
    }

    private readonly struct TypeInfoData(string ns, string name, string header, ImmutableArray<Operation> ops)
    {
        public string Namespace { get; } = ns;
        public string TypeName { get; } = name;
        public string Header { get; } = header;
        public ImmutableArray<Operation> Operators { get; } = ops;
    }

    private readonly struct Operation(string token, string a, string b, string ret)
    {
        public string OperatorToken { get; } = token;
        public string TypeA { get; } = a;
        public string TypeB { get; } = b;
        public string ReturnType { get; } = ret;
    }
}