// 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.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeCleanup;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.PasteTracking;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.AddMissingImports;
 
internal abstract class AbstractAddMissingImportsRefactoringProvider : CodeRefactoringProvider
{
    protected abstract string CodeActionTitle { get; }
 
    public override async Task ComputeRefactoringsAsync(CodeRefactoringContext context)
    {
        var (document, _, cancellationToken) = context;
 
        // If we aren't in a host that supports paste tracking (known by having exactly one export of type
        // IPasteTrackingService), we can't do anything. This is just to avoid creating MEF part rejections for
        // things composing the Features layer.
        var services = document.Project.Solution.Workspace.Services.HostServices as IMefHostExportProvider;
        var pasteTrackingService = services?.GetExports<IPasteTrackingService>().SingleOrDefault()?.Value;
        if (pasteTrackingService is null)
            return;
 
        // Currently this refactoring requires the SourceTextContainer to have a pasted text span.
        var sourceText = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
        if (!pasteTrackingService.TryGetPastedTextSpan(sourceText.Container, out var textSpan))
        {
            return;
        }
 
        // Check pasted text span for missing imports
        var addMissingImportsService = document.GetRequiredLanguageService<IAddMissingImportsFeatureService>();
 
        var analysis = await addMissingImportsService.AnalyzeAsync(document, textSpan, cancellationToken).ConfigureAwait(false);
        if (!analysis.CanAddMissingImports)
        {
            return;
        }
 
        var addImportsCodeAction = CodeAction.Create(
            CodeActionTitle,
            async (progressTracker, cancellationToken) =>
                (await addMissingImportsService.AddMissingImportsAsync(document, analysis, progressTracker, cancellationToken).ConfigureAwait(false)).Project.Solution,
            CodeActionTitle);
 
        context.RegisterRefactoring(addImportsCodeAction, textSpan);
    }
}