/*  Submitted by:   Maderal, Kurt Merkell John P.
//                  ICS 20 A
//                  Xavier University
//
//
//
//  An implementation of a List-Based Queues
*/

import java.io.*;

public class QueueList
{
    public BufferedReader ItemReader;
    private int size, check;
    private Node head, tail;
    private String programName;
    private String inp3;

    public QueueList(String n) throws IOException
    {
        programName = n;
        size=0;
        check=0;
        System.out.println("\n   -------------------- List-Based Queue --------------------\n");
        instruct();
        access();
    }

    public void enqueue(Object obj)
    {
        System.out.println("                      Enqueued :     "+ obj);

        Node node = new Node();
        node.setElement(obj);
        node.setNext(null); // node will be new tail node

        if (size==0)
        {
            head = node; // special case if a previously empty queue
        }
        else
            tail.setNext(node); //add node at the tail of the list

        tail = node;  //update the reference to the tail node
        size++;
    }

    public void dequeue()
    {
        Object obj=null;

        if (size==0)
            System.out.println("                      Error..!!!  "+ programName.toUpperCase() +" is Empty...");
        else
            obj = head.getElement();
            head = head.getNext();
            size--;

        if (size == 0)
            tail = null; // the queue is now empty
        System.out.println("                      Dequeued :     "+ obj.toString());
    }


    //inner class Node for the reference
    public class Node
    {
        //instance variables
        private Object element;
        private Node next;

        //simple constructor
        public Node() { this(null,null); }
        public Node (Object o, Node n) { element=o; next=n; }

        //accessor methods
        public Object getElement() { return element; }
        public Node getNext() { return next; }

        //modifier methods
        public void setElement(Object newElem) { element=newElem; }
        public void setNext(Node newNext) { next=newNext; }
    }

    //main
    public static void main(String args[]) throws IOException
    {
       QueueList list = new QueueList("List-Based Queue");
    }

    // method instructions
    public void instruct()
    {
        System.out.println("\nCommands for Methods: type  \" e \" for "+"\"Enqueue\""+"     with your Input...");
        System.out.println("                            \" d \" for "+"\"Dequeue\"");
        System.out.println("                            \" f \" for "+"\"Front\"");
        System.out.println("                            \" y \" for "+"\"IsEmpty?\"");
        System.out.println("                            \" r \" for "+"\"Reset All\"");
        System.out.println("                            \" a \" for "+"\"Displaying all Inputs\"");
        System.out.println("                            \" i \" for "+"\"Commands / Instructions / HELP\"");
        System.out.println("                            \" x \" for "+"\"Exit Program\"\n\n");
        System.out.println("                    --------> NOTE  :     NO SPACES.... <--------\n\n");
    }  

    //method access() for starting
    public void access() throws IOException
    {
        // "infinite for loop" so that inputs are ask over and over
        // if check == -1 then loop terminates and reset method is called
        for (; ; )
        {
            inputs();
            if (check==-1)
            {
                break;
            }
        }
        reset();
    }

    //reset method that calls for a new Object of type Queues
    public void reset() throws IOException
    {
        QueueList ql = new QueueList("List-Based Queues");
    }

    //method inputs()
    public void inputs() throws IOException
    {
        ItemReader = new BufferedReader(new InputStreamReader(System.in));
        System.out.print("Type Command:  ");
        inp3 = ItemReader.readLine();
        String com3 = (inp3.charAt(0)+"");


            if ( (com3.equals("e"))||(com3.equals("d"))||(com3.equals("f"))||(com3.equals("y"))||(com3.equals("x"))||(com3.equals("r"))||(com3.equals("a"))||(com3.equals("i")) )
            {
                if (com3.equals("e"))
                {
                    String s3 = "";
                    for (int i=1; i<inp3.length(); i++)
                    {
                        s3 += (inp3.charAt(i)+"");
                    }
                        enqueue(new String(s3));
                }
                if (com3.equals("d"))
                {
                    dequeue();
                }
                if (com3.equals("f"))
                {
                    front();
                }
                if (com3.equals("y"))
                {
                    System.out.println("                      IsEmpty? :     "+ IsEmpty());
                }
                if (com3.equals("x"))
                {
                    System.out.println("\n\n                      Program Terminated...");
                    System.exit(0);
                }
                if (com3.equals("a"))
                {
                    displayInputs();
                }
                if (com3.equals("i"))
                {
                    instruct();
                }
                if (com3.equals("r"))
                {
                    check = -1;
                }
            }
            else
                {
                    System.out.print("                      Command Not Found!...\n");
                }
    }//end of method -->  inputs ( )

    //display all the remaining inputs from the list
    public void displayInputs()
    {
        Node current = head;

        if (size==0)
        {
            System.out.println("                      Error..!!!  "+ programName.toUpperCase() +" is Empty...");
            return;
        }
            System.out.print("\nALL Stored inputs  :-->>   ");

            while (current != null)
            {
               System.out.print(current.element.toString()+ ", ");//.next from class Node
               current = current.next;
            }
            System.out.println("\n");
    }

    // method IsEmpty : returns " true " if queue is Empty, " false " otherwise
    public boolean IsEmpty( )
    {
        return size==0;
    }

    // method front : return and show the item / element that will be dequeued next
    public void front()
    {
        if (size==0)
        {
            System.out.println("                      Error..!!!  "+ programName.toUpperCase() +" is Empty...");
        }
        else
            System.out.println("                      Front    :     "+ head.getElement().toString() );
    }
}