// 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.

using System.Linq;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace Microsoft.CodeAnalysis.CSharp.Extensions;

internal static class ILocalSymbolExtensions
{
    public static bool CanSafelyMoveLocalToBlock(this ILocalSymbol localSymbol, SyntaxNode currentBlock, SyntaxNode destinationBlock)
    {
        if (currentBlock != destinationBlock)
        {
            var localFunctionOrMethodDeclaration = currentBlock.AncestorsAndSelf()
                .FirstOrDefault(node => node.Kind() is SyntaxKind.LocalFunctionStatement or SyntaxKind.MethodDeclaration);
            var localFunctionStatement = destinationBlock.FirstAncestorOrSelf<LocalFunctionStatementSyntax>();

            if (localFunctionOrMethodDeclaration != localFunctionStatement &&
                HasTypeParameterWithName(localFunctionOrMethodDeclaration, localSymbol.Type.Name) &&
                HasTypeParameterWithName(localFunctionStatement, localSymbol.Type.Name))
            {
                return false;
            }
        }

        return true;

        static bool HasTypeParameterWithName(SyntaxNode? node, string name)
        {
            SeparatedSyntaxList<TypeParameterSyntax>? typeParameters;
            switch (node)
            {
                case MethodDeclarationSyntax methodDeclaration:
                    typeParameters = methodDeclaration.TypeParameterList?.Parameters;
                    break;
                case LocalFunctionStatementSyntax localFunctionStatement:
                    typeParameters = localFunctionStatement.TypeParameterList?.Parameters;
                    break;
                default:
                    return false;
            }

            return typeParameters.HasValue && typeParameters.Value.Any(typeParameter => typeParameter.Identifier.ValueText == name);
        }
    }
}