// 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.Collections.Immutable;
using System.Composition;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.CodeRefactorings.SyncNamespace;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Text;
 
namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.SyncNamespace
{
    [ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.SyncNamespace), Shared]
    internal sealed class CSharpSyncNamespaceCodeRefactoringProvider
        : AbstractSyncNamespaceCodeRefactoringProvider<BaseNamespaceDeclarationSyntax, CompilationUnitSyntax, MemberDeclarationSyntax>
    {
        [ImportingConstructor]
        [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
        public CSharpSyncNamespaceCodeRefactoringProvider()
        {
        }
 
        protected override async Task<SyntaxNode?> TryGetApplicableInvocationNodeAsync(Document document, TextSpan span, CancellationToken cancellationToken)
        {
            if (!span.IsEmpty)
                return null;
 
            if (await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false) is not CompilationUnitSyntax compilationUnit)
                return null;
 
            var position = span.Start;
            var namespaceDecls = compilationUnit.DescendantNodes(n => n is CompilationUnitSyntax or BaseNamespaceDeclarationSyntax)
                .OfType<BaseNamespaceDeclarationSyntax>().ToImmutableArray();
 
            if (namespaceDecls.Length == 1 && compilationUnit.Members.Count == 1)
            {
                var namespaceDeclaration = namespaceDecls[0];
                if (namespaceDeclaration.Name.Span.IntersectsWith(position))
                    return namespaceDeclaration;
            }
 
            if (namespaceDecls.Length == 0)
            {
                var firstMemberDeclarationName = compilationUnit.Members.FirstOrDefault().GetNameToken();
 
                if (firstMemberDeclarationName != default
                    && firstMemberDeclarationName.Span.IntersectsWith(position))
                {
                    return compilationUnit;
                }
            }
 
            return null;
        }
 
        protected override string EscapeIdentifier(string identifier)
            => identifier.EscapeIdentifier();
    }
}