// 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 Microsoft.CodeAnalysis.CSharp.LanguageService;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Operations;
using Microsoft.CodeAnalysis.SimplifyLinqExpression;
 
namespace Microsoft.CodeAnalysis.CSharp.SimplifyLinqExpression
{
    [DiagnosticAnalyzer(LanguageNames.CSharp)]
    internal sealed class CSharpSimplifyLinqExpressionDiagnosticAnalyzer : AbstractSimplifyLinqExpressionDiagnosticAnalyzer<InvocationExpressionSyntax, MemberAccessExpressionSyntax>
    {
        protected override ISyntaxFacts SyntaxFacts => CSharpSyntaxFacts.Instance;
 
        protected override IInvocationOperation? TryGetNextInvocationInChain(IInvocationOperation invocation)
            // In C#, exention methods contain the methods they are being called from in the `this` parameter 
            // So in the case of A().ExensionB() to get to ExensionB from A we do the following:
            => invocation.Parent is IArgumentOperation argument &&
               argument.Parent is IInvocationOperation nextInvocation
                    ? nextInvocation
                    : null;
    }
}