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

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

struct Node {
  QueueElement element;
  struct Node* next;
};

struct Node* last = NULL;

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

int enqueue(QueueElement element) {
  struct Node* newNode = (struct Node*)malloc(sizeof(struct Node));
  newNode->element = element;
  
  if (last == NULL) {
    //The queue is empty.
    newNode->next = newNode;
  } else {
    //The queue is not empty.
    newNode->next = last->next;
    last->next = newNode;
  }
  last = newNode;

  //There is allways room for a new node.
  return 0;
}

int dequeue(QueueElement *element) {
  if (last == NULL) {
    //The queue is empty, return error code (-1).
    return -1;
  } else {
    *element = last->next->element;
    struct Node* tmp = last->next;
    if (last->next == last->next->next) {
      //There is only one node left in the queue.
      last = NULL;
    } else {
      last->next = last->next->next;
    }
    free(tmp);
    
    return 0;
  }
}