#define MAX_CARS 3
#define EAST 0
#define WEST 1
#define ANY 2

#include <iostream.h>
#include "synch.h"

/* The following procedures are protected by a monitor */

Lock *mylock = new Lock("amylock");
int currentDirection = ANY; // the flow of traffic on the bridge
int cars = 0;                      // The number of cars on the bridge
int waiters = 0;                   // cars waiting for space on the bridge

Condition* lessThanMax = new Condition ("max");
Condition* directionChange = new Condition ("change");
char* strings[2] = {"East","West"};

void CrossBridge (int myDirection) {
  cout <<  "Crossing the bridge" << endl;
}

void ArriveBridge (int myDirection) {
  mylock->Acquire();
  
  while (currentDirection != myDirection && currentDirection != ANY) {
    directionChange->Wait(mylock);
  }

  if (currentDirection != myDirection) {
    currentDirection = myDirection;
    cout << "Changed direction to: " << strings[myDirection] << endl;
  }
  
  while (cars == MAX_CARS) {
    waiters++;
    lessThanMax->Wait(mylock);
    waiters--;
  }

  cars++;
  cout << "Car crossing from the " << strings[myDirection] << endl;
  mylock->Release();
}

void ExitBridge (int myDirection) {
  mylock->Acquire();

  cout << "Car leaving from the " << strings[myDirection] << endl;  
  cars--;  
  lessThanMax->Signal(mylock);
      
  if (cars == 0 && waiters == 0) {
    currentDirection = ANY;
    directionChange->Broadcast(mylock);
  }

  mylock->Release();
}