// Chap 7, pp 339 - 341
// Rename this file as EL.h

//**********************************************************
// Header file EL.h for ADT event list.
// The event list contains events that are sorted by the
// time of the event. There are two kinds of events:
//   Arrival:   Person enters the line. Event is represented
//              by the arrival time and transaction time.
//   Departure: Person completes transaction and leaves the 
//              line. Event is represented by the departure 
//              time.
//**********************************************************
#include <stddef.h>     // defines NULL
#include <iostream.h>
#include "boolean.h"

enum eventKind {A, D};  // 2 kinds of events

struct event
{
   eventKind WhichEvent;  // A (arrival) or D (departure)
   int       Time;        // time of event
   int       TransTime;   // transaction time; used
                          // for arrival events only
   // constructors:
   event();
   event(eventKind KindOfEvent, int EventTime,
         int TransactionTime);
};  // end struct

struct eventNode;       // defined in implementation file
typedef eventNode* eventPtrType;

class eventListClass
{
public:
// constructors and destructor:
   eventListClass();
   eventListClass(const eventListClass& E);
   ~eventListClass();

// event list operations:
   boolean EventListIsEmpty();
   // Determines whether the event list is empty.
   // Precondition: The constructor has been called.
   // Postcondition: Returns TRUE if the event list is 
   // empty, otherwise returns FALSE.

   void InsertEvent(event NewEvent, boolean& Success);
   // Inserts an event into the event list in its proper 
   // order by time.
   // Precondition: The constructor has been called. 
   // NewEvent is the event to be added to the list.
   // Postcondition: If insertion is successful, NewEvent is 
   // added to the event list such that times are ordered
   // (if events have the same times, arrival events come
   // before departure events) and Success is TRUE. 
   // Otherwise, Success is FALSE.

   void DeleteEvent(boolean& Success);
   // Deletes the first event in the event list.
   // Precondition: The constructor has been called.
   // Postcondition: If deletion is successful, the first
   // event is deleted and Success is TRUE. Otherwise, the
   // event list is unchanged and Success is FALSE.

   void RetrieveEvent(event& FirstEvent, boolean& Success);
   // Retrieves the first event in the event list.
   // Precondition: The constructor has been called.
   // Postcondition: If retrieval is successful, the first
   // event is copied into FirstEvent and Success is TRUE. 
   // Otherwise, FirstEvent is unchanged and Success is
   // FALSE.

private:
   eventPtrType EL;  // pointer to linked event list
};  // end class
// End of header file.