// 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.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeCleanup;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.FileHeaders;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.AddFileBanner;

internal abstract class AbstractAddFileBannerNewDocumentFormattingProvider : INewDocumentFormattingProvider
{
    protected abstract SyntaxGenerator SyntaxGenerator { get; }
    protected abstract SyntaxGeneratorInternal SyntaxGeneratorInternal { get; }
    protected abstract AbstractFileHeaderHelper FileHeaderHelper { get; }

    public async Task<Document> FormatNewDocumentAsync(Document document, Document? hintDocument, CodeCleanupOptions options, CancellationToken cancellationToken)
    {
        var rootToFormat = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);

        // Apply file header preferences
        var fileHeaderTemplate = options.DocumentFormattingOptions.FileHeaderTemplate;
        if (!string.IsNullOrEmpty(fileHeaderTemplate))
        {
            var newLineTrivia = SyntaxGeneratorInternal.EndOfLine(options.FormattingOptions.NewLine);
            var rootWithFileHeader = await AbstractFileHeaderCodeFixProvider.GetTransformedSyntaxRootAsync(
                SyntaxGenerator.SyntaxFacts,
                FileHeaderHelper,
                newLineTrivia,
                document,
                fileHeaderTemplate,
                cancellationToken).ConfigureAwait(false);

            return document.WithSyntaxRoot(rootWithFileHeader);
        }
        else if (hintDocument is not null)
        {
            // If there is no file header preference, see if we can use the one in the hint document
            var bannerService = hintDocument.GetRequiredLanguageService<IFileBannerFactsService>();
            var hintSyntaxRoot = await hintDocument.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
            var fileBanner = bannerService.GetFileBanner(hintSyntaxRoot);

            var rootWithBanner = rootToFormat.WithPrependedLeadingTrivia(fileBanner);
            return document.WithSyntaxRoot(rootWithBanner);
        }

        return document;
    }
}