// 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;
using System.Collections.Immutable;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using Microsoft.CodeAnalysis.CodeFixesAndRefactorings;
 
namespace Microsoft.CodeAnalysis.CSharp.CodeFixesAndRefactorings;
 
[ExportLanguageService(typeof(IFixAllSpanMappingService), LanguageNames.CSharp), Shared]
internal sealed class CSharpFixAllSpanMappingService : AbstractFixAllSpanMappingService
{
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public CSharpFixAllSpanMappingService()
    {
    }
 
    protected override async Task<ImmutableDictionary<Document, ImmutableArray<TextSpan>>> GetFixAllSpansIfWithinGlobalStatementAsync(
        Document document, TextSpan span, CancellationToken cancellationToken)
    {
        var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
        var node = root.FindNode(span);
        if (node.GetAncestorOrThis<GlobalStatementSyntax>() is null)
            return ImmutableDictionary<Document, ImmutableArray<TextSpan>>.Empty;
 
        // Compute the fix all span for the global statements to be fixed.
        // If the file has type or namespace declaration towards the end, they need to be excluded
        // from the fix all span.
        var fixAllSpan = root.FullSpan;
        var firstTypeOrNamespaceDecl = root.ChildNodes().FirstOrDefault(n => SyntaxFacts.IsNamespaceMemberDeclaration(n.Kind()));
        if (firstTypeOrNamespaceDecl is not null)
        {
            // Bail out for compiler error case where a type or namespace declaration precedes a global statement.
            // C# compiler requires all global statements to preceed type and namespace declarations.
            var globalStatements = root.ChildNodes().OfType<GlobalStatementSyntax>();
            if (globalStatements.Any(g => firstTypeOrNamespaceDecl.SpanStart < g.SpanStart))
                return ImmutableDictionary<Document, ImmutableArray<TextSpan>>.Empty;
 
            fixAllSpan = new TextSpan(root.FullSpan.Start, firstTypeOrNamespaceDecl.FullSpan.Start - 1);
        }
 
        return ImmutableDictionary<Document, ImmutableArray<TextSpan>>.Empty
            .Add(document, [fixAllSpan]);
    }
}