// 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.Immutable;
using System.Composition;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
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;
using Microsoft.CodeAnalysis.Shared.Utilities;
 
namespace Microsoft.CodeAnalysis.UseSystemHashCode;
 
[ExportCodeFixProvider(LanguageNames.CSharp, LanguageNames.VisualBasic, Name = PredefinedCodeFixProviderNames.UseSystemHashCode), Shared]
[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 UseSystemHashCodeCodeFixProvider() : SyntaxEditorBasedCodeFixProvider
{
    public override ImmutableArray<string> FixableDiagnosticIds { get; }
        = [IDEDiagnosticIds.UseSystemHashCode];
 
    public override Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        RegisterCodeFix(context, AnalyzersResources.Use_System_HashCode, nameof(AnalyzersResources.Use_System_HashCode));
        return Task.CompletedTask;
    }
 
    protected override async Task FixAllAsync(
        Document document, ImmutableArray<Diagnostic> diagnostics,
        SyntaxEditor editor, CancellationToken cancellationToken)
    {
        var generator = SyntaxGenerator.GetGenerator(document);
        var generatorInternal = document.GetRequiredLanguageService<SyntaxGeneratorInternal>();
        var declarationService = document.GetLanguageService<ISymbolDeclarationService>();
        if (declarationService == null)
        {
            return;
        }
 
        var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
        if (!HashCodeAnalyzer.TryGetAnalyzer(semanticModel.Compilation, out var analyzer))
        {
            Debug.Fail("Could not get analyzer");
            return;
        }
 
        foreach (var diagnostic in diagnostics)
        {
            var operationLocation = diagnostic.AdditionalLocations[0].FindNode(cancellationToken);
            var operation = semanticModel.GetOperation(operationLocation, cancellationToken);
 
            var methodDecl = diagnostic.AdditionalLocations[1].FindNode(cancellationToken);
            var method = semanticModel.GetDeclaredSymbol(methodDecl, cancellationToken);
            if (method == null)
                continue;
 
            var methodBlock = declarationService.GetDeclarations(method)[0].GetSyntax(cancellationToken);
 
            var (accessesBase, members, _) = analyzer.GetHashedMembers(method, operation);
            if (accessesBase || !members.IsDefaultOrEmpty)
            {
                // Produce the new statements for the GetHashCode method and replace the
                // existing ones with them.
 
                // Only if there was a base.GetHashCode() do we pass in the ContainingType
                // so that we generate the same.
                var containingType = accessesBase ? method!.ContainingType : null;
                var components = generator.GetGetHashCodeComponents(
                    generatorInternal, semanticModel.Compilation, containingType, members, justMemberReference: true);
 
                var updatedDecl = generator.WithStatements(
                    methodBlock,
                    generator.CreateGetHashCodeStatementsUsingSystemHashCode(
                        generatorInternal, analyzer.SystemHashCodeType, components));
                editor.ReplaceNode(methodBlock, updatedDecl);
            }
        }
    }
}