// 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.Collections.Immutable;
using System.Composition;
using System.Diagnostics.CodeAnalysis;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.CSharp.MakeRefStruct
{
    [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.MakeRefStruct), Shared]
    internal class MakeRefStructCodeFixProvider : CodeFixProvider
    {
        // Error CS8345: Field or auto-implemented property cannot be of certain type unless it is an instance member of a ref struct.
        private const string CS8345 = nameof(CS8345);

        [ImportingConstructor]
        [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
        public MakeRefStructCodeFixProvider()
        {
        }

        public override ImmutableArray<string> FixableDiagnosticIds
            => ImmutableArray.Create(CS8345);

        public override FixAllProvider? GetFixAllProvider()
        {
            // The chance of needing fix-all in these cases is super low
            return null;
        }

        public override async Task RegisterCodeFixesAsync(CodeFixContext context)
        {
            var document = context.Document;
            var cancellationToken = context.CancellationToken;
            var span = context.Span;

            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);

            // Could be declared in a class or even in a nested class inside a struct,
            // so find only the first parent declaration
            if (root.FindNode(span).GetAncestor<TypeDeclarationSyntax>() is not StructDeclarationSyntax structDeclaration)
                return;

            var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
            var structDeclarationSymbol = (INamedTypeSymbol)semanticModel.GetRequiredDeclaredSymbol(structDeclaration, cancellationToken);

            // CS8345 could be triggered when struct is already marked with `ref` but a property is static
            if (!structDeclarationSymbol.IsRefLikeType)
            {
                context.RegisterCodeFix(
                    CodeAction.Create(
                        CSharpCodeFixesResources.Make_ref_struct,
                        c => FixCodeAsync(document, structDeclaration, c),
                        nameof(CSharpCodeFixesResources.Make_ref_struct)),
                    context.Diagnostics);
            }
        }

        private static async Task<Document> FixCodeAsync(
            Document document,
            StructDeclarationSyntax structDeclaration,
            CancellationToken cancellationToken)
        {
            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
            var generator = SyntaxGenerator.GetGenerator(document);

            var newStruct = generator.WithModifiers(
                structDeclaration,
                generator.GetModifiers(structDeclaration).WithIsRef(true));
            var newRoot = root.ReplaceNode(structDeclaration, newStruct);

            return document.WithSyntaxRoot(newRoot);
        }
    }
}
