// 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.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.RemoveRedundantEquality
{
    [ExportCodeFixProvider(LanguageNames.CSharp, LanguageNames.VisualBasic, Name = PredefinedCodeFixProviderNames.RemoveRedundantEquality), Shared]
    internal sealed class RemoveRedundantEqualityCodeFixProvider
        : SyntaxEditorBasedCodeFixProvider
    {
        [ImportingConstructor]
        [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
        public RemoveRedundantEqualityCodeFixProvider()
        {
        }
 
        public override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(IDEDiagnosticIds.RemoveRedundantEqualityDiagnosticId);
 
        public override Task RegisterCodeFixesAsync(CodeFixContext context)
        {
            foreach (var diagnostic in context.Diagnostics)
            {
                RegisterCodeFix(context, AnalyzersResources.Remove_redundant_equality, nameof(AnalyzersResources.Remove_redundant_equality), diagnostic);
            }
 
            return Task.CompletedTask;
        }
 
        protected override async Task FixAllAsync(Document document, ImmutableArray<Diagnostic> diagnostics, SyntaxEditor editor, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)
        {
            var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
            var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
            foreach (var diagnostic in diagnostics)
            {
                var node = root.FindNode(diagnostic.AdditionalLocations[0].SourceSpan, getInnermostNodeForTie: true);
 
                editor.ReplaceNode(node, (n, _) =>
                {
                    if (!syntaxFacts.IsBinaryExpression(n))
                    {
                        // This should happen only in error cases.
                        return n;
                    }
 
                    syntaxFacts.GetPartsOfBinaryExpression(n, out var left, out var right);
                    if (diagnostic.Properties[RedundantEqualityConstants.RedundantSide] == RedundantEqualityConstants.Right)
                    {
                        return WithElasticTrailingTrivia(left);
                    }
                    else if (diagnostic.Properties[RedundantEqualityConstants.RedundantSide] == RedundantEqualityConstants.Left)
                    {
                        return WithElasticTrailingTrivia(right);
                    }
 
                    return n;
                });
            }
 
            return;
 
            static SyntaxNode WithElasticTrailingTrivia(SyntaxNode node)
            {
                return node.WithTrailingTrivia(node.GetTrailingTrivia().Select(SyntaxTriviaExtensions.AsElastic));
            }
        }
    }
}