// 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.Collections.Generic;
using System.Collections.Immutable;
using System.Composition;
using System.Diagnostics.CodeAnalysis;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.RemoveUnnecessarySuppressions;

#if !CODE_STYLE // Not exported in CodeStyle layer: https://github.com/dotnet/roslyn/issues/47942
[ExportCodeFixProvider(LanguageNames.CSharp, LanguageNames.VisualBasic, Name = PredefinedCodeFixProviderNames.RemoveUnnecessaryPragmaSuppressions), Shared]
#endif
[method: ImportingConstructor]
[method: SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
internal sealed class RemoveUnnecessaryInlineSuppressionsCodeFixProvider() : SyntaxEditorBasedCodeFixProvider
{
    public override ImmutableArray<string> FixableDiagnosticIds
        => [IDEDiagnosticIds.RemoveUnnecessarySuppressionDiagnosticId];

    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        var root = await context.Document.GetRequiredSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
        var syntaxFacts = context.Document.GetRequiredLanguageService<ISyntaxFactsService>();
        foreach (var diagnostic in context.Diagnostics)
        {
            // Defensive check that we are operating on the diagnostic on a pragma.
            if (root.FindNode(diagnostic.Location.SourceSpan) is { } node && syntaxFacts.IsAttribute(node) ||
                root.FindTrivia(diagnostic.Location.SourceSpan.Start).HasStructure)
            {
                RegisterCodeFix(context, AnalyzersResources.Remove_unnecessary_suppression, nameof(AnalyzersResources.Remove_unnecessary_suppression));
            }
        }
    }

    protected override async Task FixAllAsync(Document document, ImmutableArray<Diagnostic> diagnostics, SyntaxEditor editor, CancellationToken cancellationToken)
    {
        // We need to track unique set of processed nodes when removing the nodes.
        // This is because we generate an unnecessary pragma suppression diagnostic at both the pragma disable and matching pragma restore location
        // with the corresponding restore/disable location as an additional location to be removed.
        // Our code fix ensures that we remove both the disable and restore directives with a single code fix application.
        // So, we need to ensure that we do not attempt to remove the same node multiple times when performing a FixAll in document operation.
        using var _ = PooledHashSet<SyntaxNode>.GetInstance(out var processedNodes);
        var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
        foreach (var diagnostic in diagnostics)
        {
            RemoveNode(diagnostic.Location, editor, processedNodes, syntaxFacts);

            foreach (var location in diagnostic.AdditionalLocations)
            {
                RemoveNode(location, editor, processedNodes, syntaxFacts);
            }
        }

        return;

        static void RemoveNode(
            Location location,
            SyntaxEditor editor,
            HashSet<SyntaxNode> processedNodes,
            ISyntaxFacts syntaxFacts)
        {
            SyntaxNode node;
            var options = SyntaxGenerator.DefaultRemoveOptions;
            if (editor.OriginalRoot.FindNode(location.SourceSpan) is { } attribute &&
                syntaxFacts.IsAttribute(attribute))
            {
                node = attribute;
                // Keep leading trivia for attributes as we don't want to remove doc comments, or anything else
                options |= SyntaxRemoveOptions.KeepLeadingTrivia;
            }
            else
            {
                node = editor.OriginalRoot.FindTrivia(location.SourceSpan.Start).GetStructure()!;
            }

            if (processedNodes.Add(node))
            {
                editor.RemoveNode(node, options);
            }
        }
    }
}