﻿// 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.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.CSharp.Analyzers.ConvertProgram;
using Microsoft.CodeAnalysis.CSharp.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.ConvertProgram
{
    using static ConvertProgramAnalysis;
    using static ConvertProgramTransform;

    [ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.ConvertToProgramMain), Shared]
    internal class ConvertToProgramMainCodeRefactoringProvider : CodeRefactoringProvider
    {
        [ImportingConstructor]
        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
        public ConvertToProgramMainCodeRefactoringProvider()
        {
        }

        public override async Task ComputeRefactoringsAsync(CodeRefactoringContext context)
        {
            var (document, span, cancellationToken) = context;
            if (!span.IsEmpty)
                return;

            if (!IsApplication(document.Project.CompilationOptions!))
                return;

            var position = span.Start;
            var root = (CompilationUnitSyntax)await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);

            if (!root.IsTopLevelProgram())
                return;

            var acceptableLocation = GetUseProgramMainDiagnosticLocation(root, isHidden: true);
            if (!acceptableLocation.SourceSpan.IntersectsWith(position))
                return;

            var options = await document.GetCSharpCodeFixOptionsProviderAsync(context.Options, cancellationToken).ConfigureAwait(false);

            var compilation = await document.Project.GetRequiredCompilationAsync(cancellationToken).ConfigureAwait(false);
            if (!CanOfferUseProgramMain(options.PreferTopLevelStatements, root, compilation, forAnalyzer: false))
                return;

            context.RegisterRefactoring(CodeAction.Create(
                CSharpAnalyzersResources.Convert_to_Program_Main_style_program,
                c => ConvertToProgramMainAsync(document, options.AccessibilityModifiersRequired.Value, c),
                nameof(CSharpAnalyzersResources.Convert_to_Program_Main_style_program),
                CodeActionPriority.Low));
        }
    }
}
