/*
 * The MIT License
 * Copyright © 2014-2019 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package com.iluwatar.commander.queue;

import com.iluwatar.commander.exceptions.IsEmptyException;

/**
 * Queue data structure implementation.
 *
 * @param <T> is the type of object the queue will hold.
 */

public class Queue<T> {

  private Node<T> front;
  private Node<T> rear;
  private int size;

  static class Node<V> {
    V value;
    Node<V> next;

    Node(V obj, Node<V> b) {
      value = obj;
      next = b;
    }
  }

  /**
   * Queue constructor.
   */
  Queue() {
    front = null;
    rear = null;
    size = 0;
  }

  boolean isEmpty() {
    return size == 0;
  }

  void enqueue(T obj) {
    if (front == null) {
      front = new Node<>(obj, null);
      rear = front;
    } else {
      var temp = new Node<>(obj, null);
      rear.next = temp;
      rear = temp;
    }
    size++;
  }

  T dequeue() throws IsEmptyException {
    if (isEmpty()) {
      throw new IsEmptyException();
    } else {
      var temp = front;
      front = front.next;
      size = size - 1;
      return temp.value;
    }
  }

  T peek() throws IsEmptyException {
    if (isEmpty()) {
      throw new IsEmptyException();
    } else {
      return front.value;
    }
  }
}
