ServerComm.h

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#ifndef SERVER_COMM_H
#define SERVER_COMM_H
 
#include <string>
#include <vector>
using namespace std;
#include <curl/curl.h> //curl
#include "./data_src/EarthquakeUSGS.h"
#include "./data_src/Game.h"
#include "./data_src/Shakespeare.h"
#include "./data_src/GutenbergBook.h"
#include "./data_src/CancerIncidence.h"
#include "./data_src/ActorMovieIMDB.h"
#include "./data_src/Song.h"
#include "bridges_exception.h"
 
namespace bridges {
 
    class ServerComm {
            //Used to access to this class private functions
            friend class Bridges;
            friend class DataSource;
 
            ServerComm() = delete; //Prevents instantiation
 
            static size_t curlWriteFunction(void *contents, size_t size,
                size_t nmemb, void *results) {
                size_t handled = size * nmemb;
                if (results) {
                    ((string*)results)->append((char*)contents, handled);
                }
                return handled;
            }
            static string makeRequest(const string& url, const vector<string>&
                headers, const string& data = "") {
                string results;
                string returned_headers;
                // first load curl enviornment (only need be called
                // once in entire session tho)
                curl_global_init(CURL_GLOBAL_ALL);
                CURL* curl = curl_easy_init(); // get a curl handle
                if (curl) {
                    char error_buffer[CURL_ERROR_SIZE];
                    CURLcode res;
                    //setting verbose
                    if (0) {
                        res = curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
                        if (res != CURLE_OK)
                            throw "curl_easy_setopt failed";
                    }
                    // setting error buffer
                    res = curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, error_buffer);
                    if (res != CURLE_OK)
                        throw "curl_easy_setopt failed";
 
                    // set the URL to GET from
                    res = curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
                    if (res != CURLE_OK)
                        throw "curl_easy_setopt failed";
                    //pass pointer to callback function
                    res = curl_easy_setopt(curl, CURLOPT_WRITEDATA, &results);
                    if (res != CURLE_OK)
                        throw "curl_easy_setopt failed";
                    //sends all data to this function
                    res = curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, curlWriteFunction);
                    if (res != CURLE_OK)
                        throw "curl_easy_setopt failed";
                    //sends all header to this function
                    res = curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, curlWriteFunction);
                    //pass pointer to callback function
                    res = curl_easy_setopt(curl, CURLOPT_HEADERDATA, &returned_headers);
                    if (res != CURLE_OK)
                        throw "curl_easy_setopt failed";
                    // We should not set
                    // CURLOPT_FAILONERROR because
                    // we want the full content of
                    // the returned document and
                    // headers that may contain
                    // useful information
                    //
                    // res = curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
                    // if (res != CURLE_OK)
                    //   throw "curl_easy_setopt failed";
                    if (data.length() > 0) {
                        // Now specify the POST data
                        res = curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data.c_str());
                        if (res != CURLE_OK)
                            throw "curl_easy_setopt failed";
                        // Now specify the POST data size
                        res = curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, data.length());
                        if (res != CURLE_OK)
                            throw "curl_easy_setopt failed";
                        //  a post request
                        res = curl_easy_setopt(curl, CURLOPT_POST, 1L);
                        if (res != CURLE_OK)
                            throw "curl_easy_setopt failed";
                    }
 
                    struct curl_slist * curlHeaders = nullptr;
                    for (const string& header : headers) {
                        curlHeaders = curl_slist_append(curlHeaders, header.c_str());
                    }
                    res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, curlHeaders);
                    if (res != CURLE_OK)
                        throw "curl_easy_setopt failed";
 
                    // Perform the request, res will get the return code
                    res = curl_easy_perform(curl);
 
                    curl_slist_free_all(curlHeaders);
 
                    if (res != CURLE_OK) {
 
                        string footer = string("Root cause: ") + string("curl_easy_perform() failed.\n")
                            + "Curl Error Code "    + to_string(res) + "\n" + curl_easy_strerror(res) + "\n"
                            + "ErrorBuffer: " + error_buffer + "\n"
                            + "Headers: " + returned_headers + "\n"
                            + "Results: " + results + "\n";
                        throw footer;
                    }
 
                    if (res == CURLE_OK) {
                        long httpcode = -1;
                        curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &httpcode);
 
                        if (httpcode >= 300) {
                            throw HTTPException(url, httpcode, returned_headers, results);
                        }
 
                    }
                    curl_easy_cleanup(curl);
                }
                else {
                    throw "curl_easy_init() failed!\nNothing retrieved from server.\n";
                }
 
                curl_global_cleanup();
                return results;
            }
 
            static std::string encodeURLPart (const std::string& s) {
                std::string returnstr;
 
                curl_global_init(CURL_GLOBAL_ALL);
                CURL* curl = curl_easy_init(); // get a curl handle
 
                char* encodedstr = curl_easy_escape (curl, s.c_str(), 0);
                returnstr = encodedstr;
 
                curl_free(encodedstr);
 
                curl_easy_cleanup(curl);
                curl_global_cleanup();
 
                return returnstr;
            }
    }; //server comm
 
}// namespace bridges
#endif