#ifndef CORE_SESSION_MQH
#define CORE_SESSION_MQH
//+------------------------------------------------------------------+
//| session.mqh - time before price: daily trading windows           |
//|                                                                  |
//| A window is a daily span in minutes since midnight SERVER time   |
//| (use HM(9, 30) for 09:30). start > end wraps past midnight, so   |
//| HM(22, 0) .. HM(6, 0) is a valid Asian-style window. The start   |
//| minute is inclusive and the end minute exclusive.                |
//|                                                                  |
//| Ids returned by defineWindow() stay valid for the object's life; |
//| removeWindow() retires an id but never hands it out again.       |
//+------------------------------------------------------------------+
#include "common.mqh"

#define SESSION_ALL_DAYS 0x7F   // bit n = weekday n, 0 = Sunday .. 6 = Saturday

class CSession
  {
private:
   struct SWindow
     {
      int            startMinute;
      int            endMinute;
      int            dayMask;
      bool           live;
     };
   SWindow           m_windows[];

   bool              covers(const SWindow &w, const datetime t) const;

public:
   static int        HM(const int hour, const int minute = 0) { return hour * 60 + minute; }

   //--- true and sessionIndex set on success; false on an invalid window
   bool              defineWindow(const int startMinute, const int endMinute, int &sessionIndex,
                                  const int dayMask = SESSION_ALL_DAYS);
   void              removeWindow(const int sessionIndex);
   //--- t = 0 means TimeCurrent(). Pass a bar's time when replaying history.
   bool              isSessionActive(const int sessionIndex, const datetime t = 0) const;
   bool              isThisTimeASession(const datetime t = 0) const { return whichSession(t) >= 0; }
   //--- id of the first live window that covers t, or -1
   int               whichSession(const datetime t = 0) const;
   int               windowCount() const;
  };

//+------------------------------------------------------------------+
bool CSession::defineWindow(const int startMinute, const int endMinute, int &sessionIndex, const int dayMask)
  {
   if(startMinute < 0 || startMinute >= 1440 || endMinute < 0 || endMinute > 1440
      || startMinute == endMinute || (dayMask & SESSION_ALL_DAYS) == 0)
      return false;

   const int n = ArraySize(m_windows);
   if(ArrayResize(m_windows, n + 1) != n + 1)
      return false;

   m_windows[n].startMinute = startMinute;
   m_windows[n].endMinute   = endMinute;
   m_windows[n].dayMask     = dayMask & SESSION_ALL_DAYS;
   m_windows[n].live        = true;
   sessionIndex = n;
   return true;
  }

void CSession::removeWindow(const int sessionIndex)
  {
   if(sessionIndex >= 0 && sessionIndex < ArraySize(m_windows))
      m_windows[sessionIndex].live = false;
  }

bool CSession::covers(const SWindow &w, const datetime t) const
  {
   MqlDateTime dt;
   TimeToStruct(t, dt);
   if((w.dayMask & (1 << dt.day_of_week)) == 0)
      return false;

   const int minute = dt.hour * 60 + dt.min;
   if(w.startMinute < w.endMinute)
      return minute >= w.startMinute && minute < w.endMinute;
   return minute >= w.startMinute || minute < w.endMinute;   // wraps midnight
  }

bool CSession::isSessionActive(const int sessionIndex, const datetime t) const
  {
   if(sessionIndex < 0 || sessionIndex >= ArraySize(m_windows) || !m_windows[sessionIndex].live)
      return false;
   return covers(m_windows[sessionIndex], t == 0 ? TimeCurrent() : t);
  }

int CSession::whichSession(const datetime t) const
  {
   const datetime when = (t == 0) ? TimeCurrent() : t;
   for(int i = 0; i < ArraySize(m_windows); i++)
     {
      if(m_windows[i].live && covers(m_windows[i], when))
         return i;
     }
   return -1;
  }

int CSession::windowCount() const
  {
   int n = 0;
   for(int i = 0; i < ArraySize(m_windows); i++)
      if(m_windows[i].live)
         n++;
   return n;
  }

#endif // CORE_SESSION_MQH