// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Threading;
using System.Threading.Tasks;
using Analyzer.Utilities;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Editing;

namespace Microsoft.CodeQuality.Analyzers.ApiDesignGuidelines
{
    /// <summary>
    /// CA2218: Override GetHashCode on overriding Equals
    /// </summary>
    public abstract class OverrideGetHashCodeOnOverridingEqualsFixer : CodeFixProvider
    {
        public sealed override FixAllProvider GetFixAllProvider()
        {
            // See https://github.com/dotnet/roslyn/blob/main/docs/analyzers/FixAllProvider.md for more information on Fix All Providers
            return WellKnownFixAllProviders.BatchFixer;
        }

        public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
        {
            SyntaxNode root = await context.Document.GetRequiredSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);

            SyntaxNode typeDeclaration = root.FindNode(context.Span);
            typeDeclaration = SyntaxGenerator.GetGenerator(context.Document).GetDeclaration(typeDeclaration);
            if (typeDeclaration == null)
            {
                return;
            }

            // CONSIDER: Do we need to confirm that System.Object.GetHashCode isn't shadowed in a base type?

            string title = MicrosoftCodeQualityAnalyzersResources.OverrideGetHashCodeOnOverridingEqualsCodeActionTitle;
            context.RegisterCodeFix(
                CodeAction.Create(
                    title,
                    cancellationToken => OverrideObjectGetHashCodeAsync(context.Document, typeDeclaration, cancellationToken),
                    equivalenceKey: title),
                context.Diagnostics);
        }

        private static async Task<Document> OverrideObjectGetHashCodeAsync(Document document, SyntaxNode typeDeclaration, CancellationToken cancellationToken)
        {
            var editor = await DocumentEditor.CreateAsync(document, cancellationToken).ConfigureAwait(false);
            var generator = editor.Generator;

            var methodDeclaration = generator.DefaultGetHashCodeOverrideDeclaration(editor.SemanticModel.Compilation);

            editor.AddMember(typeDeclaration, methodDeclaration);
            return editor.GetChangedDocument();
        }
    }
}