void OnProtocolHeader()

in src/Transport/AmqpTransportListener.cs [226:283]
50 lines of code
9 McCabe index (conditional complexity)

            void OnProtocolHeader(ByteBuffer buffer)
            {
                ProtocolHeader header = new ProtocolHeader();
                header.Decode(buffer);
                AmqpTrace.OnProtocolHeader(header, false);

                // Protocol id negotiation
                TransportProvider provider = null;
                if (!this.parent.settings.TryGetTransportProvider(header, out provider))
                {
                    Fx.Assert(provider != null, "At least on provider should be configured.");
                    this.WriteReplyHeader(new ProtocolHeader(provider.ProtocolId, provider.DefaultVersion), true);
                    return;
                }

                // Protocol version negotiation
                AmqpVersion version;
                if (!provider.TryGetVersion(header.Version, out version))
                {
                    this.WriteReplyHeader(new ProtocolHeader(provider.ProtocolId, version), true);
                    return;
                }

                TransportBase newTransport = null;
                try
                {
                    newTransport = provider.CreateTransport(this.args.Transport, false);
                }
                catch (InvalidOperationException ioe)
                {
                    // treat this the same as protocol ID/version failure
                    // which are all client config issues
                    AmqpTrace.Provider.AmqpLogError(this, "CreateTransport", ioe);
                    this.WriteReplyHeader(new ProtocolHeader(ProtocolId.Amqp, AmqpVersion.V100), true);
                    return;
                }

                if (object.ReferenceEquals(newTransport, this.args.Transport))
                {
                    if ((this.parent.settings.RequireSecureTransport && !newTransport.IsSecure) ||
                        (!this.parent.settings.AllowAnonymousConnection && !newTransport.IsAuthenticated))
                    {
                        AmqpTrace.Provider.AmqpInsecureTransport(this.parent, newTransport, newTransport.IsSecure, newTransport.IsAuthenticated);
                        this.WriteReplyHeader(this.parent.settings.GetDefaultHeader(), true);
                    }
                    else
                    {
                        this.args.UserToken = header;
                        this.parent.OnHandleTransportComplete(this.args);
                    }
                }
                else
                {
                    AmqpTrace.Provider.AmqpUpgradeTransport(this, args.Transport, newTransport);
                    this.args.Transport = newTransport;
                    this.WriteReplyHeader(header, false);
                }
            }