// 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.IO;
using System.Text;
using System.Threading;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Roslyn.Test.Utilities;
 
internal sealed class GenerateFileForEachAdditionalFileWithContentsCommented : IIncrementalGenerator
{
    public const string StepName = "AdditionalTextsAsComments";
 
    public void Initialize(IncrementalGeneratorInitializationContext context)
    {
        context.RegisterSourceOutput(context.AdditionalTextsProvider.Select((t, ct) => t).WithTrackingName(StepName), (context, additionalText) =>
            context.AddSource(
                GetGeneratedFileName(additionalText.Path),
                GenerateSourceForAdditionalFile(additionalText, context.CancellationToken)));
    }
 
    private static SourceText GenerateSourceForAdditionalFile(AdditionalText file, CancellationToken cancellationToken)
    {
        // We're going to "comment" out the contents of the file when generating this
        var sourceText = file.GetText(cancellationToken);
        Contract.ThrowIfNull(sourceText, "Failed to fetch the text of an additional file.");
 
        var changes = sourceText.Lines.SelectAsArray(l => new TextChange(new TextSpan(l.Start, length: 0), "// "));
        var generatedText = sourceText.WithChanges(changes);
 
        return SourceText.From(generatedText.ToString(), encoding: Encoding.UTF8);
    }
 
    private static string GetGeneratedFileName(string path) => $"{Path.GetFileNameWithoutExtension(path)}.generated";
}