example for sqllite on sqllix

// example of putting a dataset into SQL Lite this might have been parsed from a string
// to the server and contains the products costs and quantities
//
// for SQL Lite you will need :-
// sudo apt update
// sudo apt-cache search sqlite
// sudo apt install sqlite3
//
// To Compile as well as the header file here
// https://github.com/dmitigr/sqlixx
// you also need
// sudo apt-get install libsqlite3-dev
//
// to compile
// g++-7 -std=c++17 batch_request.cpp -o batch_request -lsqlite3
//
#include <cstdlib>
#include <iostream>
#include <string>
#include <optional>
#include "sqlixx.hpp"

#include <fstream>
#include <algorithm>
#include <map>

using namespace std;

int g_index {0};

struct product_word_t {
  unsigned char ourText[100];
  unsigned char ourNums[20];
  unsigned char ourMoneys[20];
};

// parses string input to an int or null
std::optional<double> ParseStringToDouble(string& arg)
{
    try
    {
        return { std::stod(arg,0) };                                         // converts first number
    }
    catch (...)
    {
        std::cout << "cannot convert \'" << arg << "\' to int!\n";
    }

    return { };
}

int main()
{
  namespace sqlixx = dmitigr::sqlixx;
  sqlixx::Connection c{"", SQLITE_OPEN_READWRITE | SQLITE_OPEN_MEMORY};
  product_word_t inputCatalog;
  std::string printitdesc;
  std::string printitmoneys;
  std::string printitqty;
  std::string costConvertTofloat;
  std::string qtyConvertTofloat;

  // ============= Create the table for products costs and quantity =======================
  c.execute(
    R"(
    create table if not exists prod_cost_tab(
      id integer primary key AUTOINCREMENT,
      cost real,
      qty real,
      ct text,
      printmoney text,
      printqty text,
      cb blob)
    )"
  );

  // =============== Truncate the product cost table. ======================================
  c.execute("delete from prod_cost_tab");

  // =============== set up the message object with dummy data ============================
  strcpy((char*)&inputCatalog.ourText[0],"This is an example product");
  strcpy((char*)&inputCatalog.ourMoneys[0],"$10.75");
  strcpy((char*)&inputCatalog.ourNums[0],"  5.6Kg");

  // =============== get the data from the message object =================================
  char * pout = (char*) &inputCatalog.ourText[0];
  printitdesc.append(pout);
  pout = (char*) &inputCatalog.ourMoneys[0];
  printitmoneys.append(pout);
  costConvertTofloat.append(pout+1);                                                              // append the number without the leading currency identifier
  auto cost_float = ParseStringToDouble(costConvertTofloat);

  pout = (char*) &inputCatalog.ourNums[0];
  printitqty.append(pout);
  qtyConvertTofloat.append(pout);                                                                 // append the number can have e.g kg after but no leading char
  auto qty_float = ParseStringToDouble(qtyConvertTofloat);

  // =========== Populate the table with the information passed from the structure ==========
  if ((qty_float) && (cost_float))                                                                // qty and cost are valid
  {
      auto s = c.prepare("insert into prod_cost_tab(id, cost, qty, ct, printmoney, printqty, cb) values(?, ?, ?, ?, ?, ?, ?)");
      c.execute("begin");
      s.execute(g_index, *cost_float, *qty_float, printitdesc, printitmoneys, printitqty, sqlixx::Blob{"four", 4});
      c.execute("end");
      g_index++;
  }

  // ============== Query the product cost table. ===========================================
  c.execute([](const sqlixx::Statement& s)
  {
    const auto b = s.result<sqlixx::Blob>("cb");
    const std::string_view cb{static_cast<const char*>(b.data()), b.size()};
    const auto t1 = s.result<sqlixx::Text_utf8>("ct");
    const auto t2 = s.result<std::string>("ct");
    const auto t3 = s.result<std::string_view>("ct");
    assert(!std::strcmp(t1.data(), t2.data()) && (t2 == t3));
    std::cout << "id: " << s.result<int>("id") << "\n"
              << "number cost: " << s.result<double>("cost") << "\n"
              << "quantity: " << s.result<double>("qty") << "\n"
              << "description: " << t3 << "\n"
              << "blob: " << cb << "\n";
    const auto t4 = s.result<sqlixx::Text_utf8>("printmoney");
    const auto t5 = s.result<std::string>("printmoney");
    const auto t6 = s.result<std::string_view>("printmoney");
    assert(!std::strcmp(t4.data(), t5.data()) && (t5 == t6));
    const auto t7 = s.result<sqlixx::Text_utf8>("printqty");
    const auto t8 = s.result<std::string>("printqty");
    const auto t9 = s.result<std::string_view>("printqty");
    assert(!std::strcmp(t7.data(), t8.data()) && (t8 == t9));
    //std::cout << t1 << " " << t4 << " " << t7 << std::endl;
  },
  "select * from prod_cost_tab where id >= ? and id < ?", 0,  g_index);

}