#include "queue.h"

//------------- private -----------------------

#define MAX_QUEUE_SIZE 10

int first = 0;
int last = 0;
int size = 0;
QueueElement theQueue[MAX_QUEUE_SIZE];

int nextPos(int currentPos) {
  //The next position is 0 if the current position is at the end of the array.
  return ++currentPos % MAX_QUEUE_SIZE;
}

//-------------------- public ---------------

int enqueue(QueueElement element) {
  if (size == MAX_QUEUE_SIZE) {
    //The queue is full, return error code (-1).
    return -1;
  } else {
    //The queue is not full. Enqueue and return success code (0).
    size++;
    theQueue[last] = element;
    last = nextPos(last);
    return 0;
  }
}

int dequeue(QueueElement *element) {
  if (size == 0) {
    //The queue is empty, return error code (-1).
    return -1;
  } else {
    //The queue is not empty. Dequeue and return success code (0).
    size--;
    *element = theQueue[first];
    first = nextPos(first);
    return 0;
  }
}