#include "os.h"

#include <boost/algorithm/string/split.hpp>

#include <unistd.h>

#include <fstream>
#include <vector>

using namespace std::string_literals;

namespace {

 std::string to_string(uint32_t v, size_t size)
 {
  std::string result{std::to_string(v)};

  return (size > result.size() ? std::string(size - result.size(), char('0')) : ""s) + result;
 }

 std::string to_time_string(uint32_t sec)
 {
  uint32_t days = sec / (24 * 3600);
  uint32_t hours = (sec % (24 * 3600)) / 3600;
  uint32_t minutes = (sec % 3600) / 60;
  uint32_t seconds = (sec % 60);

  return std::to_string(days) + " days, "s + to_string(hours, 2) + ":"s + to_string(minutes, 2) + ":"s + to_string(seconds, 2);
 }

 uint64_t uptime()
 {
  double uptime_seconds{};
  if (std::ifstream("/proc/uptime", std::ios::in) >> uptime_seconds)
  {
   return static_cast<uint64_t>(uptime_seconds);
  }

  return 0;
 }

} // anonymous namespace

std::string OS::uptime_host()
{
 return to_time_string(uptime());
}

std::string OS::uptime_process()
{
 std::string filepath{"/proc/self/stat"};
 std::ifstream f(filepath, std::ios::in);
 if (f.is_open()) {
  std::string line;
  std::getline(f, line);
  std::vector<std::string> elements;
  boost::algorithm::split(elements, line, [](char c){ return c == ' '; });
  if (elements.size() < 22)
   throw std::runtime_error("Bad contents of /proc/self/stat");

  long jiffies_per_second {sysconf(_SC_CLK_TCK)};
  if (jiffies_per_second == 0)
   throw std::runtime_error("Jiffies per second is 0");

  try {
   unsigned long starttime { std::stoul(elements[21])};

   unsigned long runtime = uptime() - starttime / jiffies_per_second;

   return to_time_string(runtime);
  } catch (const std::exception& ex) {
   throw std::runtime_error("Bad value in /proc/self/stat: "s + ex.what());
  }

 } else
  throw std::runtime_error("Reading /proc/self/stat");
}