/**
 * Defines the a singly-linked list class
 * @author Ryan Riley Puzon
 * @author Owehn Lagman
 */

import java.util.NoSuchElementException;

public class List {
    private class Node {
        private int data;
        private Node next;

        public Node(int data) {
            this.data = data;
            this.next = null;
        }
    }

    private int length;
    private Node first;
    private Node last;

  /****CONSTRUCTOR****/

    /**
     * Instantiates a new List with default values
     * @postcondition creates a new empty list with length of 0
     */
    public List() {
        length = 0;
        first = null;
        last = null;

    }

    /****ACCESSORS****/

    /**
     * Returns the value stored in the first node
     * @precondition length != 0
     * @return the integer value stored at node first
     * @throws NoSuchElementException when precondition is violated
     */
    public int getFirst() throws NoSuchElementException{
        if (length == 0) {
            throw new NoSuchElementException("getFirst: List is Empty. No data to access!");
        }
        return first.data;
    }

    /**
     * Returns the value stored in the last node
     * @precondition length != 0
     * @return the integer value stored in the node last
     * @throws NoSuchElementException when precondition is violated
     */
    public int getLast() throws  NoSuchElementException{
        if(length == 0) {
            throw new NoSuchElementException("getLast: List is Empty. No data to access!");
        }
        return last.data;
    }
    public int testfunction() {
        getLast();
        return 0;
    }
    /**
     * Returns the current length of the list
     * @return the length of the list from 0 to n
     */
    public int getLength() {
        return length;
    }

    /**
     * Returns whether the list is currently empty
     * @return whether the list is empty
     */
    public boolean isEmpty() {
       return length == 0;
    }

    /****MUTATORS****/

    /**
     * Creates a new first element
     * @param data the data to insert at the
     * front of the list
     * @postcondition inserts a new given data point at the front of the list and creates new first
     */
    public void addFirst(int data) {
        if (first == null) {
            first = last = new Node(data);
        } else {
            Node N = new Node(data);
            N.next = first;
            first = N;
        }
        length++;
    }

    /**
     * Creates a new last element
     * @param data the data to insert at the
     * end of the list
     * @postcondition inserts a new given data at the end of the list and creates new last
     */
    public void addLast(int data) {
        if(length==0) {
            first = last = new Node(data);
        } else {
            Node temp = new Node(data);
            last.next = temp;
            last = temp;
        }
        length++;
        return;
    }

    /**
    * removes the element at the front of the list
    * @precondition length != 0
    * @postcondition removes the first element and makes the next element in the list the new first
    * @throws NoSuchElementException when precondition is violated
    */
    public void removeFirst() throws NoSuchElementException{
        if(length == 0) {
            throw new
            NoSuchElementException("removeFirst(): Cannot remove from an empty List!");
        } else if (length == 1) {
            first = last = null;
        } else {
        first = first.next;
        }
        length--;
        return;
    }

    /**
     * removes the element at the end of the list
     * @precondition length != 0
     * @postcondition removes the last node and makes the prior element before the last the new last element of the list
     * @throws NoSuchElementException when precondition is violated
     */
      public void removeLast() throws NoSuchElementException {
          //add your if statement here
          if (length == 0) {
              throw new NoSuchElementException("removeLast(): Cannot remove from an empty List!");
          }
          else if (length == 1) {
              //add a line of code here
              first = last = null;
          } else {
              Node temp = first;
              while (temp.next != last) {
                  temp = temp.next;
              }
              last = temp;
              last.next = null;
          }
          length--;
          return;
      }

    /****ADDITIONAL OPERATIONS****/

      /**
       * List with each value separated by a blank space
       * At the end of the List a new line
       * @return the List as a String for display
       */
        @Override public String toString() {
            String result = "";
            Node temp = first;
            while(temp != null) {
                result += temp.data + " ";
                temp = temp.next;
                //fill in here
            }
            result += "\n";
            return result;
        }

}