/*
    * Copyright (C) 2009, Google Inc.
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
    *
   * All rights reserved.
   *
   * 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 the Eclipse Foundation, Inc. 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 org.eclipse.jgit.util;
  
  /**
   * Simple Map<long, Object>.
   *
   * @param <V>
   *            type of the value instance.
   * @since 4.9
   */
  public class LongMap<V> {
  	private static final float LOAD_FACTOR = 0.75f;
  
  	private Node<V>[] table;
  
  	/** Number of entries currently in the map. */
  	private int size;
  
  	/** Next {@link #size} to trigger a {@link #grow()}. */
  	private int growAt;
  
  	/**
  	 * Initialize an empty LongMap.
  	 */
  	public LongMap() {
  		table = createArray(64);
  		growAt = (int) (table.length * LOAD_FACTOR);
  	}
  
  	/**
  	 * Whether {@code key} is present in the map.
  	 *
  	 * @param key
  	 *            the key to find.
  	 * @return {@code true} if {@code key} is present in the map.
  	 */
  	public boolean containsKey(long key) {
  		return get(key) != null;
  	}
  
  	/**
  	 * Get value for this {@code key}
  	 *
  	 * @param key
  	 *            the key to find.
  	 * @return stored value for this key, or {@code null}.
  	 */
  	public V get(long key) {
  		for (Node<V> n = table[index(key)]; n != null; n = n.next) {
  			if (n.key == key)
  				return n.value;
  		}
  		return null;
  	}
  
  	/**
  	 * Remove an entry from the map
 	 *
 	 * @param key
 	 *            key to remove from the map.
 	 * @return old value of the key, or {@code null}.
 	 */
 	public V remove(long key) {
 		Node<V> n = table[index(key)];
 		Node<V> prior = null;
 		while (n != null) {
 			if (n.key == key) {
 				if (prior == null)
 					table[index(key)] = n.next;
 				else
 					prior.next = n.next;
 				size--;
 				return n.value;
 			}
 			prior = n;
 			n = n.next;
 		}
 		return null;
 	}
 
 	/**
 	 * Put a new entry into the map
 	 *
 	 * @param key
 	 *            key to store {@code value} under.
 	 * @param value
 	 *            new value.
 	 * @return prior value, or null.
 	 */
 	public V put(long key, V value) {
 		for (Node<V> n = table[index(key)]; n != null; n = n.next) {
 			if (n.key == key) {
 				final V o = n.value;
 				n.value = value;
 				return o;
 			}
 		}
 
 		if (++size == growAt)
 			grow();
 		insert(new Node<>(key, value));
 		return null;
 	}
 
 	private void insert(Node<V> n) {
 		final int idx = index(n.key);
 		n.next = table[idx];
 		table[idx] = n;
 	}
 
 	private void grow() {
 		final Node<V>[] oldTable = table;
 		final int oldSize = table.length;
 
 		table = createArray(oldSize << 1);
 		growAt = (int) (table.length * LOAD_FACTOR);
 		for (int i = 0; i < oldSize; i++) {
 			Node<V> e = oldTable[i];
 			while (e != null) {
 				final Node<V> n = e.next;
 				insert(e);
 				e = n;
 			}
 		}
 	}
 
 	private final int index(long key) {
 		int h = ((int) key) >>> 1;
 		h ^= (h >>> 20) ^ (h >>> 12);
 		return h & (table.length - 1);
 	}
 
 	@SuppressWarnings("unchecked")
 	private static final <V> Node<V>[] createArray(int sz) {
 		return new Node[sz];
 	}
 
 	private static class Node<V> {
 		final long key;
 		V value;
 		Node<V> next;
 
 		Node(long k, V v) {
 			key = k;
 			value = v;
 		}
 	}
 }