// queue.cpp
#include <iostream.h>
#include "queue.h"

queue::queue() {
   head = NULL;
   tail = NULL;
   size = 0;
}  // end of queue constructor.

queue::~queue() {
   while (!empty()) {
      remove();
   }
}  // end of queue destructor.
   
void queue::insert(itemtype anItem) {
   node* p = new node;
   p->item = anItem;
   p->next = NULL;

   if ( empty() ) {
      tail = head = p;
   } else if (anItem != tail->item) {
      tail = tail->next = p;
   }
}  // end of method insert().

boolean queue::empty() const {
   return (head == NULL);
}  // end of method empty().

itemtype queue::remove() {
   node* temp;
   itemtype itemVal;

   if (!empty()) {
      temp = head;
      head = head->next;
      itemVal = temp->item;
      if (head == NULL) tail = NULL;
      delete temp;
   } else {
      err(UNDERFLOW);
   }

   return itemVal;
}  // end of method remove().

void queue::see() const {
   node* temp;
   
   if (!empty()) {
      temp = head;
      while (temp != NULL) {
         if (temp->next == NULL) {
            cout << temp->item;
         } else {
            cout << temp->item << ",";
         }
         temp = temp->next;
      }
   } else {
      cout << "Queue is empty.\n";
   }
}  // end of method see().

int queue::length() {
   node* temp;
   int total = 0;

   if (!empty()) {
      temp = head;
      while (temp != NULL) {
         temp = temp->next;
         total++;
      }
   }

   return total;
}
 
void queue::clear() {
   itemtype junk;
   while (!empty()) {
      junk = remove();
   }
}  // end of method clear().

itemtype queue::front() const { // get the first item of the queue.
   if (empty()) {
      err(UNDERFLOW);
   } else {
      return head->item;
   }
}  // end of method front().

void queue::err(queueError err) const {
   cout << "\nError: ";
   switch (err) {
      case UNDERFLOW: cerr << "UNDERFLOW!"; break;
      case EMPTY:     cerr <<"EMPTY!"; break;
      default:        cerr << "UNKNOWN!";
   }
}  // end of method err().