/*
 * Copyright (c) 2007, intarsys consulting GmbH
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * - Neither the name of intarsys nor the names of its contributors may be used
 *   to endorse or promote products derived from this software without specific
 *   prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package de.intarsys.tools.collection;

/**
 * <p>
 * A hash map that uses primitive ints for the key rather than objects.
 * </p>
 * 
 * <p>
 * Copied from Jakarta Commons Lang internal implementation. To be removed as
 * soon as Jakarta Commons Collections provides it.
 * </p>
 */
public class IntHashMap {
	/**
	 * The hash table data.
	 */
	private transient Entry[] table;

	/**
	 * The total number of entries in the hash table.
	 */
	private transient int count;

	/**
	 * The table is rehashed when its size exceeds this threshold. (The value of
	 * this field is (int)(capacity * loadFactor).)
	 * 
	 * @serial
	 */
	private int threshold;

	/**
	 * The load factor for the hashtable.
	 * 
	 * @serial
	 */
	private float loadFactor;

	/**
	 * <p>
	 * Innerclass that acts as a datastructure to create a new entry in the
	 * table.
	 * </p>
	 */
	private static class Entry {
		int hash;

		int key;

		Object value;

		Entry next;

		/**
		 * <p>
		 * Create a new entry with the given values.
		 * </p>
		 * 
		 * @param hash
		 *            The code used to hash the object with
		 * @param key
		 *            The key used to enter this in the table
		 * @param value
		 *            The value for this key
		 * @param next
		 *            A reference to the next entry in the table
		 */
		protected Entry(int hash, int key, Object value, Entry next) {
			this.hash = hash;
			this.key = key;
			this.value = value;
			this.next = next;
		}
	}

	/**
	 * <p>
	 * Constructs a new, empty hashtable with a default capacity and load
	 * factor, which is <code>20</code> and <code>0.75</code> respectively.
	 * </p>
	 */
	public IntHashMap() {
		this(20, 0.75f);
	}

	/**
	 * <p>
	 * Constructs a new, empty hashtable with the specified initial capacity and
	 * default load factor, which is <code>0.75</code>.
	 * </p>
	 * 
	 * @param initialCapacity
	 *            the initial capacity of the hashtable.
	 * @throws IllegalArgumentException
	 *             if the initial capacity is less than zero.
	 */
	public IntHashMap(int initialCapacity) {
		this(initialCapacity, 0.75f);
	}

	/**
	 * <p>
	 * Constructs a new, empty hashtable with the specified initial capacity and
	 * the specified load factor.
	 * </p>
	 * 
	 * @param initialCapacity
	 *            the initial capacity of the hashtable.
	 * @param loadFactor
	 *            the load factor of the hashtable.
	 * @throws IllegalArgumentException
	 *             if the initial capacity is less than zero, or if the load
	 *             factor is nonpositive.
	 */
	public IntHashMap(int initialCapacity, float loadFactor) {
		super();
		if (initialCapacity < 0) {
			throw new IllegalArgumentException("Illegal Capacity: "
					+ initialCapacity);
		}
		if (loadFactor <= 0) {
			throw new IllegalArgumentException("Illegal Load: " + loadFactor);
		}
		if (initialCapacity == 0) {
			initialCapacity = 1;
		}

		this.loadFactor = loadFactor;
		table = new Entry[initialCapacity];
		threshold = (int) (initialCapacity * loadFactor);
	}

	/**
	 * <p>
	 * Returns the number of keys in this hashtable.
	 * </p>
	 * 
	 * @return the number of keys in this hashtable.
	 */
	public int size() {
		return count;
	}

	/**
	 * <p>
	 * Tests if this hashtable maps no keys to values.
	 * </p>
	 * 
	 * @return <code>true</code> if this hashtable maps no keys to values;
	 *         <code>false</code> otherwise.
	 */
	public boolean isEmpty() {
		return count == 0;
	}

	/**
	 * <p>
	 * Tests if some key maps into the specified value in this hashtable. This
	 * operation is more expensive than the <code>containsKey</code> method.
	 * </p>
	 * 
	 * <p>
	 * Note that this method is identical in functionality to containsValue,
	 * (which is part of the Map interface in the collections framework).
	 * </p>
	 * 
	 * @param value
	 *            a value to search for.
	 * @return <code>true</code> if and only if some key maps to the
	 *         <code>value</code> argument in this hashtable as determined by
	 *         the <tt>equals</tt> method; <code>false</code> otherwise.
	 * @throws NullPointerException
	 *             if the value is <code>null</code>.
	 * @see #containsKey(int)
	 * @see #containsValue(Object)
	 * @see java.util.Map
	 */
	public boolean contains(Object value) {
		if (value == null) {
			throw new NullPointerException();
		}

		Entry[] tab = table;
		for (int i = tab.length; i-- > 0;) {
			for (Entry e = tab[i]; e != null; e = e.next) {
				if (e.value.equals(value)) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * <p>
	 * Returns <code>true</code> if this HashMap maps one or more keys to this
	 * value.
	 * </p>
	 * 
	 * <p>
	 * Note that this method is identical in functionality to contains (which
	 * predates the Map interface).
	 * </p>
	 * 
	 * @param value
	 *            value whose presence in this HashMap is to be tested.
	 * @return boolean <code>true</code> if the value is contained
	 * @see java.util.Map
	 * @since JDK1.2
	 */
	public boolean containsValue(Object value) {
		return contains(value);
	}

	/**
	 * <p>
	 * Tests if the specified object is a key in this hashtable.
	 * </p>
	 * 
	 * @param key
	 *            possible key.
	 * @return <code>true</code> if and only if the specified object is a key
	 *         in this hashtable, as determined by the <tt>equals</tt> method;
	 *         <code>false</code> otherwise.
	 * @see #contains(Object)
	 */
	public boolean containsKey(int key) {
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index]; e != null; e = e.next) {
			if (e.hash == hash) {
				return true;
			}
		}
		return false;
	}

	/**
	 * <p>
	 * Returns the value to which the specified key is mapped in this map.
	 * </p>
	 * 
	 * @param key
	 *            a key in the hashtable.
	 * @return the value to which the key is mapped in this hashtable;
	 *         <code>null</code> if the key is not mapped to any value in this
	 *         hashtable.
	 * @see #put(int, Object)
	 */
	public Object get(int key) {
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index]; e != null; e = e.next) {
			if (e.hash == hash) {
				return e.value;
			}
		}
		return null;
	}

	/**
	 * <p>
	 * Increases the capacity of and internally reorganizes this hashtable, in
	 * order to accommodate and access its entries more efficiently.
	 * </p>
	 * 
	 * <p>
	 * This method is called automatically when the number of keys in the
	 * hashtable exceeds this hashtable's capacity and load factor.
	 * </p>
	 */
	protected void rehash() {
		int oldCapacity = table.length;
		Entry[] oldMap = table;

		int newCapacity = (oldCapacity * 2) + 1;
		Entry[] newMap = new Entry[newCapacity];

		threshold = (int) (newCapacity * loadFactor);
		table = newMap;

		for (int i = oldCapacity; i-- > 0;) {
			for (Entry old = oldMap[i]; old != null;) {
				Entry e = old;
				old = old.next;

				int index = (e.hash & 0x7FFFFFFF) % newCapacity;
				e.next = newMap[index];
				newMap[index] = e;
			}
		}
	}

	/**
	 * <p>
	 * Maps the specified <code>key</code> to the specified <code>value</code>
	 * in this hashtable. The key cannot be <code>null</code>.
	 * </p>
	 * 
	 * <p>
	 * The value can be retrieved by calling the <code>get</code> method with
	 * a key that is equal to the original key.
	 * </p>
	 * 
	 * @param key
	 *            the hashtable key.
	 * @param value
	 *            the value.
	 * @return the previous value of the specified key in this hashtable, or
	 *         <code>null</code> if it did not have one.
	 * @throws NullPointerException
	 *             if the key is <code>null</code>.
	 * @see #get(int)
	 */
	public Object put(int key, Object value) {
		// Makes sure the key is not already in the hashtable.
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index]; e != null; e = e.next) {
			if (e.hash == hash) {
				Object old = e.value;
				e.value = value;
				return old;
			}
		}

		if (count >= threshold) {
			// Rehash the table if the threshold is exceeded
			rehash();

			tab = table;
			index = (hash & 0x7FFFFFFF) % tab.length;
		}

		// Creates the new entry.
		Entry e = new Entry(hash, key, value, tab[index]);
		tab[index] = e;
		count++;
		return null;
	}

	/**
	 * <p>
	 * Removes the key (and its corresponding value) from this hashtable.
	 * </p>
	 * 
	 * <p>
	 * This method does nothing if the key is not present in the hashtable.
	 * </p>
	 * 
	 * @param key
	 *            the key that needs to be removed.
	 * @return the value to which the key had been mapped in this hashtable, or
	 *         <code>null</code> if the key did not have a mapping.
	 */
	public Object remove(int key) {
		Entry[] tab = table;
		int hash = key;
		int index = (hash & 0x7FFFFFFF) % tab.length;
		for (Entry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
			if (e.hash == hash) {
				if (prev != null) {
					prev.next = e.next;
				} else {
					tab[index] = e.next;
				}
				count--;
				Object oldValue = e.value;
				e.value = null;
				return oldValue;
			}
		}
		return null;
	}

	/**
	 * <p>
	 * Clears this hashtable so that it contains no keys.
	 * </p>
	 */
	public synchronized void clear() {
		Entry[] tab = table;
		for (int index = tab.length; --index >= 0;) {
			tab[index] = null;
		}
		count = 0;
	}
}
