// Chap 7, pp 341 - 343
// Rename this file as EL.CPP

//**********************************************************
// Implementation file EL.cpp for ADT event list.
//**********************************************************
#include "EL.h"  // header file
#include <assert.h>

event::event()
{
}  // end default constructor

event::event(eventKind KindOfEvent,
             int EventTime, int TransactionTime):
   WhichEvent(KindOfEvent), Time(EventTime),
   TransTime(TransactionTime)
{
}  // end constructor

struct eventNode  // event list node
{  event        Event;
   eventPtrType Next;
};  // end struct

eventListClass::eventListClass() : EL(NULL)
{
}  // end constructor

eventListClass::eventListClass(const eventListClass& E)
{  // Implementation left as an exercise (Exercise 10).
}  // end copy constructor

eventListClass::~eventListClass()
{  // Implementation left as an exercise (Exercise 10).
}  // end destructor

boolean eventListClass::EventListIsEmpty()
{
   return boolean(EL == NULL);
}  // end EventListIsEmpty

void eventListClass::InsertEvent(event NewEvent,
                                 boolean& Success)
{
   // create new node
   eventPtrType NewPtr = new eventNode;
   Success = boolean(NewPtr != NULL);

   if (Success)
   {  // allocation successful; set data members of new node
      NewPtr->Event = NewEvent;
      NewPtr->Next = NULL;

      // if the event list is empty, simply add node
      if (EL == NULL)
      EL = NewPtr;

      // else if event list is not empty, insert new node
      // at front or end of list according to times of new 
      // event and first event on list:

      // case 1 - new event is earlier or is an arrival 
      // event at same time: insert at front of list
      else if ( (NewPtr->Event.Time <  EL->Event.Time) ||
              ( (NewPtr->Event.Time == EL->Event.Time) &&
                (NewPtr->Event.WhichEvent == A) ) )
      {  NewPtr->Next = EL;
         EL = NewPtr;
      }  // end else

      // case 2 - new event is later or is a departure
      // event at same time: insert at end of list
      else
      {  NewPtr->Next = NULL;
         EL->Next = NewPtr;
      }  // end if
   }  // end if
}  // end InsertEvent

void eventListClass::DeleteEvent(boolean& Success)
{
   Success = boolean(!EventListIsEmpty());

   if (Success)
      EL = EL -> Next;
}  // end DeleteEvent

void eventListClass::RetrieveEvent(event& FirstEvent,
                                   boolean& Success)
{
   Success = boolean(!EventListIsEmpty());

   if (Success)
      FirstEvent = EL->Event;
}  // end RetrieveEvent
// End of implementation file.