package DataStructures.DynamicArray;

import java.util.*;

/**
 * This class implements a dynamic array
 * @param <E> the type that each index of the array will hold
 */
public class DynamicArray<E> implements Iterable<E> {

 private int capacity;
 private int size;
 private Object[] elements;

 /**
 * constructor
 * @param capacity the starting length of the desired array
 */
 public DynamicArray(final int capacity) {
 	this.size = 0;
 this.capacity = capacity;
 this.elements = new Object[this.capacity];
 }

 /**
 * No-args constructor
 */
 public DynamicArray() {
 	this.size = 0;
 	this.capacity = 10;
 this.elements = new Object[this.capacity];
 }

 /**
 * Doubles the capacity of the array
 * @return int the new capacity of the array
 */
 public int newCapacity() {
 this.capacity *= 2; 
 //changed from this.capacity <<= 1; now much easier to understand
 return this.capacity;
 }

 /**
 * Adds an element to the array
 * If full, creates a copy array twice the size of the current one
 * @param element the element of type <E> to be added to the array
 */
 public void add(final E element) {
 if (this.size == this.elements.length) {
 	this.elements = Arrays.copyOf(this.elements, newCapacity());
 }

 this.elements[this.size] = element;
 size++;
 }
 
 /**
 * Places element of type <E> at the desired index
 * @param index the index for the element to be placed
 * @param element the element to be inserted
 */
 public void put(final int index, E element) {
 this.elements[index] = element;
 }

 /**
 * get method for element at a given index
 * returns null if the index is empty
 * @param index the desired index of the element
 * @return <E> the element at the specified index
 */
 public E get(final int index) {
 return getElement(index);
 }
 
 /**
 * Removes an element from the array
 * @param index the index of the element to be removed
 * @return <E> the element removed
 */
 public E remove(final int index) {
 final E oldElement = getElement(index);
 fastRemove(this.elements, index);

 return oldElement;
 }
 
 /**
 * get method for size field
 * @return int size
 */
 public int getSize() {
 return this.size;
 }

 /**
 * isEmpty helper method
 * @return boolean true if the array contains no elements, false otherwise
 */
 public boolean isEmpty() {
 return this.size == 0;
 }
 
 public Stream<E> stream() {
 return StreamSupport.stream(spliterator(), false);
 }

 private void fastRemove(final Object[] elements, final int index) {
 final int newSize = this.size - 1;

 if (newSize > index) {
 	System.arraycopy(elements, index + 1, elements, index, newSize - index);
 }

 elements[this.size = newSize] = null;
 }

 private E getElement(final int index) {
 return (E) this.elements[index];
 }

 /**
 * returns a String representation of this object
 * @return String a String representing the array
 */
 @Override
 public String toString() {
 return Arrays.toString(Arrays.stream(this.elements).filter(Objects::nonNull).toArray());
 }

 /**
 * Creates and returns a new Dynamic Array Iterator
 * @return Iterator a Dynamic Array Iterator
 */
 @Override
 public Iterator iterator() {
 return new DynamicArrayIterator();
 }

 private class DynamicArrayIterator implements Iterator<E> {

 private int cursor;

 @Override
 public boolean hasNext() {
 return this.cursor != size;
 }

 @Override
 public E next() {
 if (this.cursor > DynamicArray.this.size) throw new NoSuchElementException();

 if (this.cursor > DynamicArray.this.elements.length) throw new ConcurrentModificationException();

 final E element = DynamicArray.this.getElement(this.cursor);
 this.cursor++;

 return element;
 }

 @Override
 public void remove() {
 if (this.cursor < 0) throw new IllegalStateException();

 DynamicArray.this.remove(this.cursor);
 this.cursor--;
 }

 @Override
 public void forEachRemaining(Consumer<? super E> action) {
 Objects.requireNonNull(action);

 for (int i = 0; i < DynamicArray.this.size; i++) {
 action.accept(DynamicArray.this.getElement(i));
 }
 }
 }

 /**
 * This class is the driver for the DynamicArray<E> class
 * it tests a variety of methods and prints the output
 */
 public static void main(String[] args) {
 DynamicArray<String> names = new DynamicArray<>();
 names.add("Peubes");
 names.add("Marley");

 for (String name : names) {
 System.out.println(name);
 }

 names.stream().forEach(System.out::println);

 System.out.println(names);

 System.out.println(names.getSize());

 names.remove(0);

 for (String name : names) {
 System.out.println(name);
 }
 }
}