// 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.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.CSharp.Analyzers.ConvertProgram;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Formatting;
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.ConvertToTopLevelStatements), Shared]
internal sealed class ConvertToTopLevelStatementsCodeRefactoringProvider : CodeRefactoringProvider
{
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public ConvertToTopLevelStatementsCodeRefactoringProvider()
    {
    }

    public override async Task ComputeRefactoringsAsync(CodeRefactoringContext context)
    {
        var (document, span, cancellationToken) = context;

        // can only suggest moving to top level statement on c# 9 or above.
        if (document.Project.ParseOptions!.LanguageVersion() < LanguageVersion.CSharp9 ||
            !IsApplication(document.Project.CompilationOptions!))
        {
            return;
        }

        var methodDeclaration = await context.TryGetRelevantNodeAsync<MethodDeclarationSyntax>().ConfigureAwait(false);
        if (methodDeclaration is null)
            return;

        var options = await document.GetCSharpSyntaxFormattingOptionsAsync(cancellationToken).ConfigureAwait(false);
        if (!CanOfferUseTopLevelStatements(options.PreferTopLevelStatements, forAnalyzer: false))
            return;

        var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
        var compilation = semanticModel.Compilation;

        if (!IsProgramMainMethod(semanticModel, methodDeclaration, GetMainTypeName(compilation), cancellationToken, out var canConvert) ||
            !canConvert)
        {
            return;
        }

        context.RegisterRefactoring(CodeAction.Create(
            CSharpAnalyzersResources.Convert_to_top_level_statements,
            c => ConvertToTopLevelStatementsAsync(document, methodDeclaration, c),
            nameof(CSharpAnalyzersResources.Convert_to_top_level_statements),
            CodeActionPriority.Low));
    }
}