//+------------------------------------------------------------------+
//|                                              GenerateCases.mq5   |
//|                     CalendarDifference Test Generator            |
//+------------------------------------------------------------------+
#property script_show_inputs

#include "..\TimeUtils.mqh"

input int RandomPairs = 100000;

const datetime MIN_TIME = D'1970.01.01 00:00:00';
const datetime MAX_TIME = D'3000.12.31 23:59:59';

//---------------------------------------------------------------
// SplitMix64
//---------------------------------------------------------------
struct SplitMix64
{
   ulong state;

   SplitMix64()
   {
      state = (ulong)GetTickCount64();
   }

   ulong Next()
   {
      ulong z = (state += 0x9E3779B97F4A7C15);
      z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9;
      z = (z ^ (z >> 27)) * 0x94D049BB133111EB;
      return z ^ (z >> 31);
   }
};

SplitMix64 RNG;

//---------------------------------------------------------------

string ISO(datetime t)
{
   MqlDateTime s;
   TimeToStructFast(t, s);

   return StringFormat("%04d-%02d-%02dT%02d:%02d:%02d",
                       s.year,
                       s.mon,
                       s.day,
                       s.hour,
                       s.min,
                       s.sec);
}

//---------------------------------------------------------------

void WritePair(int file,
               datetime from,
               datetime to)
{
   MqlDateTime diff;
   CalendarDifference(from, to, diff);

   FileWrite(file,
             ISO(from),
             ISO(to),
             diff.year,
             diff.mon,
             diff.day,
             diff.hour,
             diff.min,
             diff.sec);
}

//+------------------------------------------------------------------+
//| Writes the pair only if both timestamps are in range             |
//+------------------------------------------------------------------+
void WritePairIfValid(const int file,
                      const datetime from,
                      const datetime to)
{
   if(to < MIN_TIME || to > MAX_TIME)
      return;

   WritePair(file, from, to);
}

//---------------------------------------------------------------

datetime RandomTime()
{
   ulong span = (ulong)(MAX_TIME - MIN_TIME);

   return (datetime)(MIN_TIME + (datetime)(RNG.Next() % span));
}

//---------------------------------------------------------------

void GenerateMonthEnds(int file)
{
   for(int year=1970; year<=3000; year++)
   {
      for(int month=1; month<=12; month++)
      {
         int last=DaysInMonth(year,month);

         for(int day=MathMax(1,last-3); day<=last; day++)
         {
            datetime t=DateFrom(year,month,day);

            WritePairIfValid(file, t, AddDays(t, -2));
            WritePairIfValid(file, t, AddDays(t, -1));
            WritePairIfValid(file, t, AddDays(t, 1));
            WritePairIfValid(file, t, AddDays(t, 2));

            WritePairIfValid(file, t, AddMonths(t, -1));
            WritePairIfValid(file, t, AddMonths(t, 1));

            WritePairIfValid(file, t, AddYears(t, -1));
            WritePairIfValid(file, t, AddYears(t, 1));
         }
      }
   }
}

//---------------------------------------------------------------

void GenerateLeapYears(int file)
{
   for(int year=1970; year<=3000; year++)
   {
      if(!IsLeapYear(year))
         continue;

      datetime feb28=DateFrom(year,2,28);

      WritePairIfValid(file,feb28,AddDays(feb28,1));
      WritePairIfValid(file,feb28,AddDays(feb28,2));

      datetime feb29=DateFrom(year,2,29);

      WritePairIfValid(file,feb29,AddYears(feb29,1));
      WritePairIfValid(file,feb29,AddYears(feb29,4));

      WritePairIfValid(file,feb29,AddMonths(feb29,12));
   }
}

//---------------------------------------------------------------

void GenerateYearBoundaries(int file)
{
   for(int year=1970; year<=3000; year++)
   {
      datetime end=DateFrom(year,12,31,23,59,59);

      WritePairIfValid(file,end,AddSeconds(end,1));
      WritePairIfValid(file,end,AddDays(end,1));
      WritePairIfValid(file,end,AddMonths(end,1));
      WritePairIfValid(file,end,AddYears(end,1));
   }
}

//---------------------------------------------------------------

void GenerateQuarterBoundaries(int file)
{
   const int months[]={3,6,9,12};

   for(int year=1970; year<=3000; year++)
   {
      for(int i=0;i<4;i++)
      {
         int month=months[i];

         datetime t=DateFrom(
             year,
             month,
             DaysInMonth(year,month));

         WritePairIfValid(file,t,AddDays(t,1));
         WritePairIfValid(file,t,AddMonths(t,3));
      }
   }
}

//---------------------------------------------------------------

void GenerateRandom(int file)
{
   for(int i=0;i<RandomPairs;i++)
   {
      WritePairIfValid(file,
                       RandomTime(),
                       RandomTime());
   }
}

//---------------------------------------------------------------

void OnStart()
{
   int file = FileOpen(
      "CalendarDifferenceCases.csv",
      FILE_WRITE | FILE_CSV | FILE_ANSI,
      ','
   );

   if(file == INVALID_HANDLE)
   {
      Print("FileOpen() failed. Error = ", GetLastError());
      return;
   }

   FileWrite(file,
             "from",
             "to",
             "years",
             "months",
             "days",
             "hours",
             "minutes",
             "seconds");

   GenerateMonthEnds(file);

   GenerateLeapYears(file);

   GenerateQuarterBoundaries(file);

   GenerateYearBoundaries(file);

   GenerateRandom(file);

   FileClose(file);

   Print("CalendarDifferenceCases.csv generated.");
}