#include "queue.h"


void enqueue(Node **head, Node **tail, int value) {

  Node *new_node = (Node*)malloc(sizeof(Node));

  if ( ! new_node ) {
    fprintf(stderr,"Error: Out of memory");
    return;
  }

  new_node->value = value;
  new_node->next = NULL;
  
  // Case 1: queue is empty
  if ( is_empty(*head) ) {
    *head = new_node;
  } 
  // Case 2: queue is not empty
  else {
    (*tail)->next = new_node;
  }

  *tail = new_node;
  
}


// Pre-condition: queue cannot be empty
int dequeue(Node **head, Node **tail) {

  Node *removed = *head;

  *head = (*head)->next;

  if ( !(*head) ) {
    *tail = NULL;
  }
    
  int value = removed->value;
  free(removed);

  return value;
}


bool is_empty(Node *head) {
  return (head == NULL);
}


void print(Node *head) {

  Node *current = head;

  while ( current ) {
    printf("%d ", current->value);
    current = current->next;
  }
  printf("\n");

}