AbstractClientSessionCRTP.h

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regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"; you may not use this file except in compliance
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  http://www.apache.org/licenses/LICENSE-2.0
 
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software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
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-----------------------------------------------------------------------*/
#pragma once
 
#include "ClientSession.h"
 
namespace ETP_NS
{
    // This uses the Curiously Recurring Template Pattern so that the same code works with both SSL streams and regular sockets.
    template<class Derived>
    class AbstractClientSessionCRTP : public ETP_NS::ClientSession
    {
    public:
 
        virtual ~AbstractClientSessionCRTP() = default;
 
        void on_ssl_handshake(boost::system::error_code ec) {
            if (ec) {
                std::cerr << "ERROR at Websocket connection : " << ec.message() << std::endl;
                return;
            }
 
#if BOOST_VERSION < 107000
            // Perform the websocket handshake
            derived().ws()->async_handshake_ex(responseType,
                etpServerHost + ":" + etpServerPort, etpServerTarget,
                [&](websocket::request_type& m)
                {
                    m.insert(boost::beast::http::field::sec_websocket_protocol, "etp12.energistics.org");
                    m.insert(boost::beast::http::field::authorization, etpServerAuthorization);
                    if (!proxyHost.empty() && !isTls()) {
                        m.insert(boost::beast::http::field::proxy_authorization, proxyAuthorization);
                    }
                    m.insert("etp-encoding", "binary");
                    for (const auto& mapEntry : additionalHandshakeHeaderFields_) {
                        m.insert(mapEntry.first, mapEntry.second);
                    }
                },
                std::bind(
                    &ClientSession::on_handshake,
                    std::static_pointer_cast<AbstractClientSessionCRTP>(shared_from_this()),
                    std::placeholders::_1));
#else
            derived().ws()->set_option(websocket::stream_base::decorator(
                [&](websocket::request_type& m)
                {
                    m.insert(boost::beast::http::field::sec_websocket_protocol, "etp12.energistics.org");
                    m.insert(boost::beast::http::field::authorization, etpServerAuthorization);
                    if (!proxyHost.empty() && !isTls()) {
                        m.insert(boost::beast::http::field::proxy_authorization, proxyAuthorization);
                    }
                    m.insert("etp-encoding", "binary");
                    for (const auto& mapEntry : additionalHandshakeHeaderFields_) {
                        m.insert(mapEntry.first, mapEntry.second);
                    }
                })
            );
            // Perform the websocket handshake
            derived().ws()->async_handshake(responseType,
                etpServerHost + ":" + etpServerPort, etpServerTarget,
                std::bind(
                    &ClientSession::on_handshake,
                    std::static_pointer_cast<AbstractClientSessionCRTP>(shared_from_this()),
                    std::placeholders::_1));
#endif
        }

        FETPAPI_DLL_IMPORT_OR_EXPORT void do_close() {
            derived().ws()->async_close(websocket::close_code::normal,
                std::bind(
                    &AbstractSession::on_close,
                    shared_from_this(),
                    std::placeholders::_1));
        }
        
        FETPAPI_DLL_IMPORT_OR_EXPORT void do_read()
        {
            if (webSocketSessionClosed) {
                fesapi_log("CLOSED : NOTHING MORE TO DO");
                return;
            }
 
            // Read a message into our buffer
            derived().ws()->async_read(
                receivedBuffer,
                std::bind(
                    &AbstractSession::on_read,
                    shared_from_this(),
                    std::placeholders::_1,
                    std::placeholders::_2));
        }
 
        void setMaxWebSocketMessagePayloadSize(uint64_t value) final {
            maxWebSocketMessagePayloadSize = value;
            derived().ws()->read_message_max(value);
        }
 
    protected:
        using ClientSession::ClientSession;
 
        // Access the derived class, this is part of the Curiously Recurring Template Pattern idiom.
        Derived& derived() { return static_cast<Derived&>(*this); }
 
        void do_write() {
            if (sendingQueue.empty()) {
                fesapi_log("The sending queue is empty.");
                return;
            }
 
            auto& front = sendingQueue.front();
            const std::lock_guard<std::mutex> specificProtocolHandlersLock(specificProtocolHandlersMutex);
            bool previousSentMessageCompleted = specificProtocolHandlers.find(std::get<0>(front)->messageHeader.messageId) == specificProtocolHandlers.end();
 
            if (!previousSentMessageCompleted) {
                fesapi_log("Cannot send Message id :", std::to_string(std::get<0>(front)->messageHeader.messageId), "because the previous message has not finished to be sent.");
            }
            else {
                fesapi_log("Sending Message id :", std::to_string(std::get<0>(front)->messageHeader.messageId));
 
                auto avroBytes = std::get<0>(front)->encodeHeaderAndBody();
 
                //asio::buffer is a non-owning view. We must keep the underlying storage alive until the I/O completes.
                if (avroBytes->size() < maxWebSocketMessagePayloadSize) {
                    derived().ws()->async_write(
                        boost::asio::buffer(*avroBytes),
                        [this, self{ this->shared_from_this() }, avroBytes](boost::system::error_code ec, std::size_t)
                        ->void
                    {
 
                        if (ec) {
                            std::cerr << "on_write : " << ec.message() << std::endl;
                        }
                        else {
                            // Register the handler to respond to the sent message
                            const std::lock_guard<std::mutex> specificProtocolHandlersLock(specificProtocolHandlersMutex);
                            auto& front = sendingQueue.front();
                            auto nextMessage = std::get<0>(front);
                            specificProtocolHandlers[nextMessage->messageHeader.messageId] =
                                std::make_tuple(nextMessage, std::get<1>(front), std::get<2>(front));
                        }
 
                        // Remove the sent message from the queue
                        const std::lock_guard<std::mutex> sendingQueueLock(sendingQueueMutex);
                        sendingQueue.pop();
 
                        do_write();
                    });
                }
                else {
                    throw std::invalid_argument("You cannot send a message which is too big. Please use message part or chunk or whatever else.");
                }
            }
        }
    };
}