#include <stdio.h>                                              /* queue.c */
#include <stdlib.h>
#include "queue.h"

void printQueue( Queue * q ) {
  QueueNode * n = q->head;
  while( n != NULL ) {
    printf("%c", n->data);
    n = n->nextPtr;
  }
}
void initQueue(Queue * q) { /*@{}@XPC{@I q is assumed to be non-NULL}*/
    q->head = NULL;
    q->tail = NULL;
}
Queue * newQueue() {
    Queue * q = malloc( sizeof(Queue) );
    if ( q == NULL )  { fprintf(stderr, "newQueue: out of memory!\n"); }
    else                      { initQueue(q); }
    return q;
}
/*@{}@XPC{pass by reference --- @I {q} is assumed to be non-NULL!}*/
bool enqueue( Queue * q, char c ) {
    QueueNode * n = malloc( sizeof(QueueNode) );
    if ( n == NULL ) {
        fprintf(stderr, "enqueue: out of memory!\n");
        return false;
    }
    else {
        n->data = c;
        n->nextPtr = NULL;
        if ( q->head == NULL )  { q->head = n; }
        else                                  { q->tail->nextPtr = n; }
        q->tail = n;
        return true;
    }
}
bool isEmpty( Queue * q ) { return q->head == NULL; }

/*@{}@XPC{pass by reference --- @I {q} is assumed to be non-NULL and non-empty!}*/
char dequeue( Queue * q ) {
    QueueNode * oldHead = q->head;
    char c  = oldHead->data;
    q->head = oldHead->nextPtr;
    if ( q->head == NULL )
        { q->tail = NULL; }
    free( oldHead );
    return c;
}