#include <stdio.h>

#include "../shared/MiscSupport.h"

#include "FormatTime.h"

// We assume local time is Pacific.  Some of these things always use Eastern,
// so that's 3 hours difference.
#define EASTERN_OFFSET (3*60*60)

inline bool isDigit(char ch)
{
  return (ch >= '0') && (ch <= '9');
}

static bool looksLikeMySql(std::string const &s)
{
  if (s.size() != 19)
    return false;
  char const *ch = s.c_str();
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (*ch++ != '-') return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (*ch++ != '-') return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (*ch++ != ' ') return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (*ch++ != ':') return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  if (*ch++ != ':') return false;
  if (!isDigit(*ch++)) return false;
  if (!isDigit(*ch++)) return false;
  return true;
}

int getInt(char const *&ch, int digits)
{
  int result = 0;
  while (digits--)
    {
      result *= 10;
      result += (*ch++) - '0';
    }
  return result;
}

time_t importTime(std::string const &asString)
{
  if (looksLikeMySql(asString))
    {
      struct tm brokenDown;
      char const *ch = asString.c_str();
      brokenDown.tm_year = getInt(ch, 4) - 1900;
      ch++;
      brokenDown.tm_mon = getInt(ch, 2) - 1;
      ch++;
      brokenDown.tm_mday = getInt(ch, 2);
      ch++;
      brokenDown.tm_hour = getInt(ch, 2);
      ch++;
      brokenDown.tm_min = getInt(ch, 2);
      ch++;
      brokenDown.tm_sec = getInt(ch, 2);
      brokenDown.tm_isdst = -1;  // unknown.
      return mktime(&brokenDown) - EASTERN_OFFSET;
    }
  else
    return strtollDefault(asString, 0);
}

// If forceEastern is false, we just convert the integer to a string.  If       
// forceEastern is true, we export it in the mysql format and use eastern time.
// If time_t is 0, regardless of forceEastern, we return the empty string.      
std::string exportTime(time_t asUnix, bool forceEastern)
{
  if (asUnix <= 0)
    return "";
  else if (forceEastern)
    {
      asUnix += EASTERN_OFFSET;
      struct tm brokenDown;
      localtime_r(&asUnix, &brokenDown);
      // 72 bytes seems like overkill, but that keeps some versions of the
      // compiler from giving me a warning.  This is just a normal mysql
      // date and time, like "2020-05-13 14:04:19".
      char buffer[72];
      sprintf(buffer, "%04d-%02d-%02d %02d:%02d:%02d", 
	      (int)brokenDown.tm_year + 1900, 
	      (int)brokenDown.tm_mon + 1, 
	      (int)brokenDown.tm_mday, 
	      (int)brokenDown.tm_hour, 
	      (int)brokenDown.tm_min, 
	      (int)brokenDown.tm_sec);
      return buffer;
    }
  else
    return ntoa(asUnix);
}

#ifdef UNIT_TEST_FORMAT_TIME

// g++ -Wall -O4 -o format_time_test -DUNIT_TEST_FORMAT_TIME FormatTime.C ../shared/MiscSupport.C

#include <iostream>

int main(int, char**)
{
  while (std::cin)
    {
      std::cout<<"Time?  ";
      std::string line;
      getline(std::cin, line);
      if (!std::cin)
	{
	  std::cout<<'\n';
	  break;
	}
      const time_t t = importTime(line);
      std::cout<<"Export unix:  "<<exportTime(t, false)<<'\n'
	       <<"Export Eastern:  "<<exportTime(t,true)<<'\n'
	       <<"Local:  "<<ctimeString(t)<<"\n\n";
    }
}

#endif