/*******************************************************************************
 * Copyright (c) 2004, 2012 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:
 *     Andrew Niefer (IBM Corporation) - Initial API and implementation
 *     Sergey Prigogin (Google)
 *******************************************************************************/
package org.eclipse.cdt.core.parser.util;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * @noextend This class is not intended to be subclassed by clients.
 */
public abstract class ObjectTable<T> extends HashTable implements Iterable<T> {
	protected T[] keyTable;

	@SuppressWarnings("unchecked")
	public ObjectTable(int initialSize) {
		super(initialSize);
		keyTable = (T[]) new Object[capacity()];
	}

	@Override
	@SuppressWarnings("unchecked")
	public Object clone() {
		ObjectTable<T> newTable = (ObjectTable<T>) super.clone();

		int size = capacity();
		newTable.keyTable = (T[]) new Object[size];
		System.arraycopy(keyTable, 0, newTable.keyTable, 0, keyTable.length);

		return newTable;
	}

	public List<T> toList() {
		int size = size();
		List<T> list = new ArrayList<>(size);
		for (int i = 0; i < size; i++) {
			list.add(keyAt(i));
		}
		return list;
	}

	public T keyAt(int i) {
		if (i < 0 || i > currEntry)
			return null;

		return keyTable[i];
	}

	@Override
	public void clear() {
		super.clear();
		Arrays.fill(keyTable, null);
	}

	@Override
	protected final int hash(int pos) {
		return hash(keyTable[pos]);
	}

	private int hash(Object obj) {
		return hashTable == null ? 0 : hashToOffset(obj.hashCode());
	}

	@Override
	@SuppressWarnings("unchecked")
	protected void resize(int size) {
		Object[] oldKeyTable = keyTable;
		keyTable = (T[]) new Object[size];
		System.arraycopy(oldKeyTable, 0, keyTable, 0, oldKeyTable.length);
		super.resize(size);
	}

	protected final int add(T obj) {
		int pos = lookup(obj);
		if (pos != -1)
			return pos;

		if (currEntry + 1 >= capacity()) {
			resize();
		}
		currEntry++;
		keyTable[currEntry] = obj;
		linkIntoHashTable(currEntry, hash(obj));
		return currEntry;
	}

	protected void removeEntry(int i) {
		// Remove the entry from the keyTable, shifting everything over if necessary
		int hash = hash(keyTable[i]);
		if (i < currEntry)
			System.arraycopy(keyTable, i + 1, keyTable, i, currEntry - i);

		keyTable[currEntry] = null;

		// Make sure you remove the value before calling super where currEntry will change
		removeEntry(i, hash);
	}

	protected final int lookup(Object buffer) {
		if (hashTable != null) {
			int hash = hash(buffer);

			if (hashTable[hash] == 0)
				return -1;

			int i = hashTable[hash] - 1;
			if (buffer.equals(keyTable[i]))
				return i;

			// Follow the next chain.
			for (i = nextTable[i] - 1; i >= 0 && i != nextTable[i] - 1; i = nextTable[i] - 1) {
				if (buffer.equals(keyTable[i]))
					return i;
			}

			return -1;
		}
		for (int i = 0; i <= currEntry; i++) {
			if (buffer.equals(keyTable[i]))
				return i;
		}
		return -1;
	}

	public boolean containsKey(T key) {
		return lookup(key) != -1;
	}

	public Object[] keyArray() {
		Object[] keys = new Object[size()];
		System.arraycopy(keyTable, 0, keys, 0, keys.length);
		return keys;
	}

	@SuppressWarnings("unchecked")
	public <X> X[] keyArray(Class<X> c) {
		X[] keys = (X[]) Array.newInstance(c, size());
		System.arraycopy(keyTable, 0, keys, 0, keys.length);
		return keys;
	}

	public boolean isEquivalent(ObjectTable<T> other, IObjectMatcher matcher) {
		if (size() != other.size()) {
			return false;
		}

		for (int i = 0; i < keyTable.length; i++) {
			T key1 = keyTable[i];
			T key2 = other.keyTable[i];
			if (key1 != key2 && !matcher.isEquivalent(key1, key2)) {
				return false;
			}
		}
		return true;
	}

	/**
	 * @since 5.4
	 */
	@Override
	public Iterator<T> iterator() {
		return new Iterator<T>() {
			int nextIndex;

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

			@Override
			public T next() {
				T element = keyAt(nextIndex);
				if (element == null) {
					throw new NoSuchElementException();
				}
				nextIndex++;
				return element;
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException();
			}
		};
	}

	@Override
	public String toString() {
		return Arrays.toString(keyTable);
	}
}
