http/http_client.hpp

/*
// Copyright (c) 2020 Intel Corporation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, 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 under the License.
*/
#pragma once
#include <boost/asio/strand.hpp>
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>

#include <cstdlib>
#include <functional>
#include <iostream>
#include <memory>
#include <queue>
#include <string>

namespace crow
{

static constexpr uint8_t maxRequestQueueSize = 50;

enum class ConnState
{
    initialized,
    connectInProgress,
    connectFailed,
    connected,
    sendInProgress,
    sendFailed,
    recvFailed,
    idle,
    suspended,
    closed
};

class HttpClient : public std::enable_shared_from_this<HttpClient>
{
  private:
    boost::beast::tcp_stream conn;
    boost::beast::flat_buffer buffer;
    boost::beast::http::request<boost::beast::http::string_body> req;
    boost::beast::http::response<boost::beast::http::string_body> res;
    boost::asio::ip::tcp::resolver::results_type endpoint;
    std::vector<std::pair<std::string, std::string>> headers;
    std::queue<std::string> requestDataQueue;
    ConnState state;
    std::string host;
    std::string port;
    std::string uri;
    int retryCount;
    int maxRetryAttempts;

    void doConnect()
    {
        if (state == ConnState::connectInProgress)
        {
            return;
        }
        state = ConnState::connectInProgress;

        BMCWEB_LOG_DEBUG << "Trying to connect to: " << host << ":" << port;
        // Set a timeout on the operation
        conn.expires_after(std::chrono::seconds(30));
        conn.async_connect(endpoint, [self(shared_from_this())](
                                         const boost::beast::error_code& ec,
                                         const boost::asio::ip::tcp::resolver::
                                             results_type::endpoint_type& ep) {
            if (ec)
            {
                BMCWEB_LOG_ERROR << "Connect " << ep
                                 << " failed: " << ec.message();
                self->state = ConnState::connectFailed;
                self->checkQueue();
                return;
            }
            self->state = ConnState::connected;
            BMCWEB_LOG_DEBUG << "Connected to: " << ep;

            self->checkQueue();
        });
    }

    void sendMessage(const std::string& data)
    {
        if (state == ConnState::sendInProgress)
        {
            return;
        }
        state = ConnState::sendInProgress;

        BMCWEB_LOG_DEBUG << __FUNCTION__ << "(): " << host << ":" << port;

        req.version(static_cast<int>(11)); // HTTP 1.1
        req.target(uri);
        req.method(boost::beast::http::verb::post);

        // Set headers
        for (const auto& [key, value] : headers)
        {
            req.set(key, value);
        }
        req.set(boost::beast::http::field::host, host);
        req.keep_alive(true);

        req.body() = data;
        req.prepare_payload();

        // Set a timeout on the operation
        conn.expires_after(std::chrono::seconds(30));

        // Send the HTTP request to the remote host
        boost::beast::http::async_write(
            conn, req,
            [self(shared_from_this())](const boost::beast::error_code& ec,
                                       const std::size_t& bytesTransferred) {
                if (ec)
                {
                    BMCWEB_LOG_ERROR << "sendMessage() failed: "
                                     << ec.message();
                    self->state = ConnState::sendFailed;
                    self->checkQueue();
                    return;
                }
                BMCWEB_LOG_DEBUG << "sendMessage() bytes transferred: "
                                 << bytesTransferred;
                boost::ignore_unused(bytesTransferred);

                self->recvMessage();
            });
    }

    void recvMessage()
    {
        // Receive the HTTP response
        boost::beast::http::async_read(
            conn, buffer, res,
            [self(shared_from_this())](const boost::beast::error_code& ec,
                                       const std::size_t& bytesTransferred) {
                if (ec)
                {
                    BMCWEB_LOG_ERROR << "recvMessage() failed: "
                                     << ec.message();
                    self->state = ConnState::recvFailed;
                    self->checkQueue();
                    return;
                }
                BMCWEB_LOG_DEBUG << "recvMessage() bytes transferred: "
                                 << bytesTransferred;
                boost::ignore_unused(bytesTransferred);

                // Discard received data. We are not interested.
                BMCWEB_LOG_DEBUG << "recvMessage() data: " << self->res;

                // Send is successful, Lets remove data from queue
                // check for next request data in queue.
                self->requestDataQueue.pop();
                self->state = ConnState::idle;
                self->checkQueue();
            });
    }

    void doClose()
    {
        boost::beast::error_code ec;
        conn.socket().shutdown(boost::asio::ip::tcp::socket::shutdown_both, ec);

        state = ConnState::closed;
        // not_connected happens sometimes so don't bother reporting it.
        if (ec && ec != boost::beast::errc::not_connected)
        {
            BMCWEB_LOG_ERROR << "shutdown failed: " << ec.message();
            return;
        }
        BMCWEB_LOG_DEBUG << "Connection closed gracefully";
    }

    void checkQueue(const bool newRecord = false)
    {
        if (requestDataQueue.empty())
        {
            // TODO: Having issue in keeping connection alive. So lets close if
            // nothing to be trasferred.
            doClose();

            BMCWEB_LOG_DEBUG << "requestDataQueue is empty\n";
            return;
        }

        if (retryCount >= maxRetryAttempts)
        {
            BMCWEB_LOG_ERROR << "Maximum number of retries is reached.";

            // Clear queue.
            while (!requestDataQueue.empty())
            {
                requestDataQueue.pop();
            }

            // TODO: Take 'DeliveryRetryPolicy' action.
            // For now, doing 'SuspendRetries' action.
            state = ConnState::suspended;
            return;
        }

        if ((state == ConnState::connectFailed) ||
            (state == ConnState::sendFailed) ||
            (state == ConnState::recvFailed))
        {
            if (newRecord)
            {
                // We are already running async wait and retry.
                // Since record is added to queue, it gets the
                // turn in FIFO.
                return;
            }

            retryCount++;
            // TODO: Perform async wait for retryTimeoutInterval before proceed.
        }
        else
        {
            // reset retry count.
            retryCount = 0;
        }

        switch (state)
        {
            case ConnState::connectInProgress:
            case ConnState::sendInProgress:
            case ConnState::suspended:
                // do nothing
                break;
            case ConnState::initialized:
            case ConnState::closed:
            case ConnState::connectFailed:
            case ConnState::sendFailed:
            case ConnState::recvFailed:
            {
                // After establishing the connection, checkQueue() will
                // get called and it will attempt to send data.
                doConnect();
                break;
            }
            case ConnState::connected:
            case ConnState::idle:
            {
                std::string data = requestDataQueue.front();
                sendMessage(data);
                break;
            }
            default:
                break;
        }

        return;
    }

  public:
    explicit HttpClient(boost::asio::io_context& ioc, const std::string& destIP,
                        const std::string& destPort,
                        const std::string& destUri) :
        conn(ioc),
        host(destIP), port(destPort), uri(destUri)
    {
        boost::asio::ip::tcp::resolver resolver(ioc);
        endpoint = resolver.resolve(host, port);
        state = ConnState::initialized;
        retryCount = 0;
        maxRetryAttempts = 5;
    }

    void sendData(const std::string& data)
    {
        if (state == ConnState::suspended)
        {
            return;
        }

        if (requestDataQueue.size() <= maxRequestQueueSize)
        {
            requestDataQueue.push(data);
            checkQueue(true);
        }
        else
        {
            BMCWEB_LOG_ERROR << "Request queue is full. So ignoring data.";
        }

        return;
    }

    void setHeaders(
        const std::vector<std::pair<std::string, std::string>>& httpHeaders)
    {
        headers = httpHeaders;
    }
};

} // namespace crow