private static bool TryFindNodeAtSource()

in src/Microsoft.VisualStudio.Threading.Analyzers.CodeFixes/VSTHRD002UseJtfRunCodeFixWithAwait.cs [68:143]
64 lines of code
6 McCabe index (conditional complexity)

        private static bool TryFindNodeAtSource(Diagnostic diagnostic, SyntaxNode root, [NotNullWhen(true)] out ExpressionSyntax? target, [NotNullWhen(true)] out Func<ExpressionSyntax, CancellationToken, ExpressionSyntax>? transform)
        {
            transform = null;
            target = null;

            var syntaxNode = (ExpressionSyntax)root.FindNode(diagnostic.Location.SourceSpan);
            if (syntaxNode.FirstAncestorOrSelf<AnonymousFunctionExpressionSyntax>() is object)
            {
                // We don't support converting anonymous delegates to async.
                return false;
            }

            SimpleNameSyntax? FindStaticWaitInvocation(ExpressionSyntax from)
            {
                SimpleNameSyntax? name = ((from as InvocationExpressionSyntax)?.Expression as MemberAccessExpressionSyntax)?.Name;
                return name?.Identifier.ValueText switch
                {
                    nameof(Task.WaitAny) => name,
                    nameof(Task.WaitAll) => name,
                    _ => null,
                };
            }

            ExpressionSyntax? TransformStaticWhatInvocation(ExpressionSyntax from, CancellationToken cancellationToken = default(CancellationToken))
            {
                SimpleNameSyntax? name = FindStaticWaitInvocation(from);
                var newIdentifier = name!.Identifier.ValueText switch
                {
                    nameof(Task.WaitAny) => nameof(Task.WhenAny),
                    nameof(Task.WaitAll) => nameof(Task.WhenAll),
                    _ => throw new InvalidOperationException(),
                };

                return from.ReplaceToken(name.Identifier, SyntaxFactory.Identifier(newIdentifier)).WithoutAnnotations(FixUtils.BookmarkAnnotationName);
            }

            ExpressionSyntax? FindTwoLevelDeepIdentifierInvocation(ExpressionSyntax from, CancellationToken cancellationToken = default(CancellationToken)) =>
                ((((from as InvocationExpressionSyntax)?.Expression as MemberAccessExpressionSyntax)?.Expression as InvocationExpressionSyntax)?.Expression as MemberAccessExpressionSyntax)?.Expression;
            ExpressionSyntax? FindOneLevelDeepIdentifierInvocation(ExpressionSyntax from, CancellationToken cancellationToken = default(CancellationToken)) =>
                ((from as InvocationExpressionSyntax)?.Expression as MemberAccessExpressionSyntax)?.Expression;
            ExpressionSyntax? FindParentMemberAccess(ExpressionSyntax from, CancellationToken cancellationToken = default(CancellationToken)) =>
                (from as MemberAccessExpressionSyntax)?.Expression;

            InvocationExpressionSyntax? parentInvocation = syntaxNode.FirstAncestorOrSelf<InvocationExpressionSyntax>();
            MemberAccessExpressionSyntax? parentMemberAccess = syntaxNode.FirstAncestorOrSelf<MemberAccessExpressionSyntax>();
            if (FindTwoLevelDeepIdentifierInvocation(parentInvocation) is object)
            {
                // This method will not return null for the provided 'target' argument
                transform = NullableHelpers.AsNonNullReturnUnchecked<ExpressionSyntax, CancellationToken, ExpressionSyntax>(FindTwoLevelDeepIdentifierInvocation);
                target = parentInvocation;
            }
            else if (FindStaticWaitInvocation(parentInvocation) is object)
            {
                // This method will not return null for the provided 'target' argument
                transform = NullableHelpers.AsNonNullReturnUnchecked<ExpressionSyntax, CancellationToken, ExpressionSyntax>(TransformStaticWhatInvocation);
                target = parentInvocation;
            }
            else if (FindOneLevelDeepIdentifierInvocation(parentInvocation) is object)
            {
                // This method will not return null for the provided 'target' argument
                transform = NullableHelpers.AsNonNullReturnUnchecked<ExpressionSyntax, CancellationToken, ExpressionSyntax>(FindOneLevelDeepIdentifierInvocation);
                target = parentInvocation;
            }
            else if (FindParentMemberAccess(parentMemberAccess) is object)
            {
                // This method will not return null for the provided 'target' argument
                transform = NullableHelpers.AsNonNullReturnUnchecked<ExpressionSyntax, CancellationToken, ExpressionSyntax>(FindParentMemberAccess);
                target = parentMemberAccess;
            }
            else
            {
                return false;
            }

            return true;
        }