// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
#nullable disable
 
using System;
using System.Text;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.PooledObjects;
 
namespace Microsoft.VisualStudio.LanguageServices.Implementation.CodeModel;
 
internal static class MetadataNameHelpers
{
    private static void AppendNamespace(INamespaceSymbol namespaceSymbol, StringBuilder builder)
        => builder.Append(namespaceSymbol.Name);
 
    private static void AppendNamedType(INamedTypeSymbol namedTypeSymbol, StringBuilder builder)
    {
        builder.Append(namedTypeSymbol.Name);
 
        if (namedTypeSymbol.Arity > 0)
        {
            var typeArguments = namedTypeSymbol.TypeArguments;
 
            builder.Append('`');
            builder.Append(typeArguments.Length);
 
            // Append generic arguments
            builder.Append('[');
 
            for (var i = 0; i < typeArguments.Length; i++)
            {
                if (i > 0)
                {
                    builder.Append(',');
                }
 
                builder.Append(GetMetadataName(typeArguments[i]));
            }
 
            builder.Append(']');
        }
    }
 
    private static void AppendArrayType(IArrayTypeSymbol symbol, StringBuilder builder)
    {
        builder.Append(GetMetadataName(symbol.ElementType));
 
        builder.Append('[');
        builder.Append(',', symbol.Rank - 1);
        builder.Append(']');
    }
 
    private static void AppendPointerType(IPointerTypeSymbol symbol, StringBuilder builder)
    {
        builder.Append(GetMetadataName(symbol.PointedAtType));
 
        builder.Append('*');
    }
 
    public static string GetMetadataName(ITypeSymbol typeSymbol)
    {
        if (typeSymbol.Kind == SymbolKind.TypeParameter)
        {
            throw new ArgumentException("Type parameters are not suppported", nameof(typeSymbol));
        }
 
        using var _ = ArrayBuilder<ISymbol>.GetInstance(out var parts);
 
        ISymbol symbol = typeSymbol;
        while (symbol != null)
        {
            parts.Push(symbol);
            symbol = symbol.ContainingSymbol;
        }
 
        var builder = new StringBuilder();
 
        while (parts.TryPop(out symbol))
        {
            if (builder.Length > 0)
            {
                if (symbol.ContainingSymbol is ITypeSymbol)
                {
                    builder.Append('+');
                }
                else
                {
                    builder.Append('.');
                }
            }
 
            switch (symbol.Kind)
            {
                case SymbolKind.Namespace:
                    var namespaceSymbol = (INamespaceSymbol)symbol;
                    if (!namespaceSymbol.IsGlobalNamespace)
                    {
                        AppendNamespace(namespaceSymbol, builder);
                    }
 
                    break;
 
                case SymbolKind.NamedType:
                    AppendNamedType((INamedTypeSymbol)symbol, builder);
                    break;
 
                case SymbolKind.ArrayType:
                    AppendArrayType((IArrayTypeSymbol)symbol, builder);
                    break;
 
                case SymbolKind.PointerType:
                    AppendPointerType((IPointerTypeSymbol)symbol, builder);
                    break;
            }
        }
 
        return builder.ToString();
    }
}