/*
 * Copyright (C) 2007-2017 Sebastiano Vigna
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package PACKAGE;

import java.util.Collection;
import java.util.NoSuchElementException;

/** A simple, brute-force implementation of a set based on a backing array.
 *
 * <p>The main purpose of this
 * implementation is that of wrapping cleanly the brute-force approach to the storage of a very
 * small number of items: just put them into an array and scan linearly to find an item.
 */

public class ARRAY_SET KEY_GENERIC extends ABSTRACT_SET KEY_GENERIC implements java.io.Serializable, Cloneable {

	private static final long serialVersionUID = 1L;
	/** The backing array (valid up to {@link #size}, excluded). */
	private transient KEY_TYPE[] a;
	/** The number of valid entries in {@link #a}. */
	private int size;

	/** Creates a new array set using the given backing array. The resulting set will have as many elements as the array.
	 *
	 * <p>It is responsibility of the caller that the elements of {@code a} are distinct.
	 *
	 * @param a the backing array.
	 */
	public ARRAY_SET(final KEY_TYPE[] a) {
		this.a = a;
		size = a.length;
	}

	/** Creates a new empty array set.
	 */
	public ARRAY_SET() { this.a = ARRAYS.EMPTY_ARRAY; }

	/** Creates a new empty array set of given initial capacity.
	 *
	 * @param capacity the initial capacity.
	 */
	public ARRAY_SET(final int capacity) { this.a = new KEY_TYPE[capacity]; }

	/** Creates a new array set copying the contents of a given collection.
	 * @param c a collection.
	 */
	public ARRAY_SET(COLLECTION KEY_GENERIC c) {
		this(c.size ());
		addAll(c);
	}

	/** Creates a new array set copying the contents of a given set.
	 * @param c a collection.
	 */
	public ARRAY_SET(final Collection<? extends KEY_GENERIC_CLASS> c) {
		this(c.size());
		addAll(c);
	}


	/** Creates a new array set using the given backing array and the given number of elements of the array.
	 *
	 * <p>It is responsibility of the caller that the first {@code size} elements of {@code a} are distinct.
	 *
	 * @param a the backing array.
	 * @param size the number of valid elements in {@code a}.
	 */
	public ARRAY_SET(final KEY_TYPE[] a, final int size) {
		this.a = a;
		this.size = size;
		if (size > a.length) throw new IllegalArgumentException("The provided size (" + size + ") is larger than or equal to the array size (" + a.length + ")");
	}

	private int findKey(final KEY_TYPE o) {
		for(int i = size; i-- != 0;) if (KEY_EQUALS(a[i], o)) return i;
		return -1;
	}

	@Override
	SUPPRESS_WARNINGS_KEY_UNCHECKED
	public KEY_ITERATOR KEY_GENERIC iterator() {
		return new KEY_ITERATOR KEY_GENERIC () {
			int next = 0;

			@Override
			public boolean hasNext() { return next < size; }

			@Override
			public KEY_GENERIC_TYPE NEXT_KEY() {
				if (! hasNext()) throw new NoSuchElementException();
				return KEY_GENERIC_CAST a[next++];
			}

			@Override
			public void remove() {
				final int tail = size-- - next--;
				System.arraycopy(a, next + 1, a, next, tail);
#if KEYS_REFERENCE
				a[size] = null;
#endif
			}
		};
	}

	@Override
	public boolean contains(final KEY_TYPE k) { return findKey(k) != -1; }

	@Override
	public int size() { return size; }

	@Override
	public boolean remove(final KEY_TYPE k) {
		final int pos = findKey(k);
		if (pos == -1) return false;
		final int tail = size - pos - 1;
		for(int i = 0; i < tail; i++) a[pos + i] = a[pos + i + 1];
		size--;
#if KEYS_REFERENCE
		a[size] = null;
#endif
		return true;
	}

	@Override
	public boolean add(final KEY_GENERIC_TYPE k) {
		final int pos = findKey(k);
		if (pos != -1) return false;
		if (size == a.length) {
			final KEY_TYPE[] b = new KEY_TYPE[size == 0 ? 2 : size * 2];
			for(int i = size; i-- != 0;) b[i] = a[i];
			a = b;
		}
		a[size++] = k;
		return true;
	}

	@Override
	public void clear() {
#if KEYS_REFERENCE
		java.util.Arrays.fill(a, 0, size, null);
#endif
		size = 0;
	}

	@Override
	public boolean isEmpty() { return size == 0; }

	/** Returns a deep copy of this set.
	 *
	 * <p>This method performs a deep copy of this array set; the data stored in the
	 * set, however, is not cloned. Note that this makes a difference only for object keys.
	 *
	 *  @return a deep copy of this set.
	 */
	@Override
	SUPPRESS_WARNINGS_KEY_UNCHECKED
	public ARRAY_SET KEY_GENERIC clone() {
		ARRAY_SET KEY_GENERIC c;
		try {
			c = (ARRAY_SET KEY_GENERIC)super.clone();
		}
		catch(CloneNotSupportedException cantHappen) {
			throw new InternalError();
		}
		c.a = a.clone();
		return c;
	}

	private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
		s.defaultWriteObject();
		for(int i = 0; i < size; i++) s.WRITE_KEY(a[i]);
	}

	private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
		s.defaultReadObject();
		a = new KEY_TYPE[size];
		for(int i = 0; i < size; i++) a[i] = s.READ_KEY();
	}
}
