Copyright (c) 2000, 2014 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2014 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.utils;

Adapted from a homonym class in org.eclipse.osgi. A hash table of
KeyedElements.
/** Adapted from a homonym class in org.eclipse.osgi. A hash table of
 * <code>KeyedElement</code>s.
 */

public class KeyedHashSet {
	public interface KeyedElement {

		boolean compare(KeyedElement other);

		Object getKey();

		int getKeyHashCode();
	}

	protected static final int MINIMUM_SIZE = 7;
	private int capacity;
	protected int elementCount = 0;
	protected KeyedElement[] elements;
	protected boolean replace;

	public KeyedHashSet(int capacity) {
		this(capacity, true);
	}

	public KeyedHashSet(int capacity, boolean replace) {
		elements = new KeyedElement[Math.max(MINIMUM_SIZE, capacity * 2)];
		this.replace = replace;
		this.capacity = capacity;
	}

	
Adds an element to this set. If an element with the same key already exists,
replaces it depending on the replace flag.
Returns:
true if the element was added/stored, false otherwise/**
	 * Adds an element to this set. If an element with the same key already exists,
	 * replaces it depending on the replace flag.
	 * @return true if the element was added/stored, false otherwise
	 */
	public boolean add(KeyedElement element) {
		int hash = hash(element);

		// search for an empty slot at the end of the array
		for (int i = hash; i < elements.length; i++) {
			if (elements[i] == null) {
				elements[i] = element;
				elementCount++;
				// grow if necessary
				if (shouldGrow())
					expand();
				return true;
			}
			if (elements[i].compare(element)) {
				if (replace)
					elements[i] = element;
				return replace;
			}
		}

		// search for an empty slot at the beginning of the array
		for (int i = 0; i < hash - 1; i++) {
			if (elements[i] == null) {
				elements[i] = element;
				elementCount++;
				// grow if necessary
				if (shouldGrow())
					expand();
				return true;
			}
			if (elements[i].compare(element)) {
				if (replace)
					elements[i] = element;
				return replace;
			}
		}

		// if we didn't find a free slot, then try again with the expanded set
		expand();
		return add(element);
	}

	public void clear() {
		elements = new KeyedElement[Math.max(MINIMUM_SIZE, capacity * 2)];
		elementCount = 0;
	}

	
The array isn't large enough so double its size and rehash
all its current values.
/**
	 * The array isn't large enough so double its size and rehash
	 * all its current values.
	 */
	protected void expand() {
		KeyedElement[] oldElements = elements;
		elements = new KeyedElement[elements.length * 2];

		int maxArrayIndex = elements.length - 1;
		for (KeyedElement element : oldElements) {
			if (element != null) {
				int hash = hash(element);
				while (elements[hash] != null) {
					hash++;
					if (hash > maxArrayIndex)
						hash = 0;
				}
				elements[hash] = element;
			}
		}
	}

	
Returns the set element with the given id, or null
if not found.
/**
	 * Returns the set element with the given id, or null
	 * if not found.
	 */
	public KeyedElement getByKey(Object key) {
		if (elementCount == 0)
			return null;
		int hash = keyHash(key);

		// search the last half of the array
		for (int i = hash; i < elements.length; i++) {
			KeyedElement element = elements[i];
			if (element == null)
				return null;
			if (element.getKey().equals(key))
				return element;
		}

		// search the beginning of the array
		for (int i = 0; i < hash - 1; i++) {
			KeyedElement element = elements[i];
			if (element == null)
				return null;
			if (element.getKey().equals(key))
				return element;
		}

		// nothing found so return null
		return null;
	}

	private int hash(KeyedElement key) {
		return Math.abs(key.getKeyHashCode()) % elements.length;
	}

	private int keyHash(Object key) {
		return Math.abs(key.hashCode()) % elements.length;
	}

	
The element at the given index has been removed so move
elements to keep the set properly hashed.
/**
	 * The element at the given index has been removed so move
	 * elements to keep the set properly hashed.
	 */
	protected void rehashTo(int anIndex) {

		int target = anIndex;
		int index = anIndex + 1;
		if (index >= elements.length)
			index = 0;
		KeyedElement element = elements[index];
		while (element != null) {
			int hashIndex = hash(element);
			boolean match;
			if (index < target)
				match = !(hashIndex > target || hashIndex <= index);
			else
				match = !(hashIndex > target && hashIndex <= index);
			if (match) {
				elements[target] = element;
				target = index;
			}
			index++;
			if (index >= elements.length)
				index = 0;
			element = elements[index];
		}
		elements[target] = null;
	}

	public boolean remove(KeyedElement toRemove) {
		if (elementCount == 0)
			return false;

		int hash = hash(toRemove);

		for (int i = hash; i < elements.length; i++) {
			KeyedElement element = elements[i];
			if (element == null)
				return false;
			if (element.compare(toRemove)) {
				rehashTo(i);
				elementCount--;
				return true;
			}
		}

		for (int i = 0; i < hash - 1; i++) {
			KeyedElement element = elements[i];
			if (element == null)
				return false;
			if (element.compare(toRemove)) {
				rehashTo(i);
				elementCount--;
				return true;
			}
		}
		return false;
	}

	private boolean shouldGrow() {
		return elementCount > elements.length * 0.75;
	}

	public int size() {
		return elementCount;
	}

	@Override
	public String toString() {
		StringBuilder result = new StringBuilder(100);
		result.append('{');
		boolean first = true;
		for (KeyedElement element : elements) {
			if (element != null) {
				if (first)
					first = false;
				else
					result.append(", "); //$NON-NLS-1$
				result.append(element);
			}
		}
		result.append('}');
		return result.toString();
	}
}