#include "queue.h"
#include<stdio.h>
#include<stdlib.h>

struct QueueStruct {
  int first;
  int last;
  int size;
  ElementType elems[MAX_QUEUE_SIZE];
};

void initQueue(QueueType* queue) {
  (*queue) = malloc(sizeof(QueueType));
  if (*queue) {
    (*queue)->first = 0;
    (*queue)->last = 0;
    (*queue)->size = 0;
  } else {
    printf("Error: couldn't allocate memory for queue!\n");
  }
}

void enqueue(QueueType queue, ElementType element) {
  if (queue->size < MAX_QUEUE_SIZE-1) {
    queue->elems[queue->last] = element;
    queue->last = (queue->last+1) % MAX_QUEUE_SIZE;
    queue->size++;
  } else {
    printf("Error: queue overflow\n");
    exit(0);
  }
}

void dequeue(QueueType queue, ElementType* element) {
  if (queue->size > 0) {
    (*element) = queue->elems[queue->first];
    queue->first = (queue->first+1) % MAX_QUEUE_SIZE;
    queue->size--;
  } else {
    printf("Error: queue underflow\n");
    exit(0);
  }
}

int queueSize(QueueType queue) {
  return queue->size;
}

void printQueue(QueueType queue, void (*printElement)(ElementType)) {
  int i;
  printf("QUEUE CONTAINS:\n");
  i = queue->first;
  while (i != queue->last) {
    printElement(queue->elems[i]);
    i = (i+1) % MAX_QUEUE_SIZE;
  }
  printf("--------------------------------\n");
}