content: /*
   * Copyright 2005-2010 Roger Kapsi, Sam Berlin
   *
   *   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 org.apache.cassandra.index.sasi.utils.trie;
  
  import java.util.Map;
  import java.util.SortedMap;
  
  import org.apache.cassandra.index.sasi.utils.trie.Cursor.Decision;
  
  /**
   * This class is taken from https://github.com/rkapsi/patricia-trie (v0.6), and slightly modified
   * to correspond to Cassandra code style, as the only Patricia Trie implementation,
   * which supports pluggable key comparators (e.g. commons-collections PatriciaTrie (which is based
   * on rkapsi/patricia-trie project) only supports String keys)
   * but unfortunately is not deployed to the maven central as a downloadable artifact.
   */
  
  /**
   * Defines the interface for a prefix tree, an ordered tree data structure. For
   * more information, see <a href="http://en.wikipedia.org/wiki/Trie">Tries</a>.
   *
   * @author Roger Kapsi
   * @author Sam Berlin
   */
  public interface Trie<K, V> extends SortedMap<K, V>
  {
      /**
       * Returns the {@link Map.Entry} whose key is closest in a bitwise XOR
       * metric to the given key. This is NOT lexicographic closeness.
       * For example, given the keys:
       *
       * <ol>
       * <li>D = 1000100
       * <li>H = 1001000
       * <li>L = 1001100
       * </ol>
       *
       * If the {@link Trie} contained 'H' and 'L', a lookup of 'D' would
       * return 'L', because the XOR distance between D &amp; L is smaller
       * than the XOR distance between D &amp; H.
       *
       * @return The {@link Map.Entry} whose key is closest in a bitwise XOR metric
       * to the provided key.
       */
      Map.Entry<K, V> select(K key);
  
      /**
       * Returns the key that is closest in a bitwise XOR metric to the
       * provided key. This is NOT lexicographic closeness!
       *
       * For example, given the keys:
       *
       * <ol>
       * <li>D = 1000100
       * <li>H = 1001000
       * <li>L = 1001100
       * </ol>
       *
       * If the {@link Trie} contained 'H' and 'L', a lookup of 'D' would
       * return 'L', because the XOR distance between D &amp; L is smaller
       * than the XOR distance between D &amp; H.
       *
       * @return The key that is closest in a bitwise XOR metric to the provided key.
       */
      @SuppressWarnings("unused")
      K selectKey(K key);
  
      /**
       * Returns the value whose key is closest in a bitwise XOR metric to
       * the provided key. This is NOT lexicographic closeness!
       *
       * For example, given the keys:
       *
       * <ol>
       * <li>D = 1000100
       * <li>H = 1001000
       * <li>L = 1001100
       * </ol>
       *
       * If the {@link Trie} contained 'H' and 'L', a lookup of 'D' would
       * return 'L', because the XOR distance between D &amp; L is smaller
       * than the XOR distance between D &amp; H.
       *
       * @return The value whose key is closest in a bitwise XOR metric
       * to the provided key.
       */
      @SuppressWarnings("unused")
      V selectValue(K key);
  
      /**
       * Iterates through the {@link Trie}, starting with the entry whose bitwise
       * value is closest in an XOR metric to the given key. After the closest
       * entry is found, the {@link Trie} will call select on that entry and continue
       * calling select for each entry (traversing in order of XOR closeness,
       * NOT lexicographically) until the cursor returns {@link Decision#EXIT}.
       *
       * <p>The cursor can return {@link Decision#CONTINUE} to continue traversing.
       *
       * <p>{@link Decision#REMOVE_AND_EXIT} is used to remove the current element
       * and stop traversing.
       *
       * <p>Note: The {@link Decision#REMOVE} operation is not supported.
       *
       * @return The entry the cursor returned {@link Decision#EXIT} on, or null
       * if it continued till the end.
       */
      Map.Entry<K,V> select(K key, Cursor<? super K, ? super V> cursor);
  
      /**
       * Traverses the {@link Trie} in lexicographical order.
       * {@link Cursor#select(java.util.Map.Entry)} will be called on each entry.
       *
       * <p>The traversal will stop when the cursor returns {@link Decision#EXIT},
       * {@link Decision#CONTINUE} is used to continue traversing and
       * {@link Decision#REMOVE} is used to remove the element that was selected
       * and continue traversing.
       *
       * <p>{@link Decision#REMOVE_AND_EXIT} is used to remove the current element
       * and stop traversing.
       *
       * @return The entry the cursor returned {@link Decision#EXIT} on, or null
       * if it continued till the end.
       */
      Map.Entry<K,V> traverse(Cursor<? super K, ? super V> cursor);
  
      /**
       * Returns a view of this {@link Trie} of all elements that are prefixed
       * by the given key.
       *
       * <p>In a {@link Trie} with fixed size keys, this is essentially a
       * {@link #get(Object)} operation.
       *
       * <p>For example, if the {@link Trie} contains 'Anna', 'Anael',
       * 'Analu', 'Andreas', 'Andrea', 'Andres', and 'Anatole', then
       * a lookup of 'And' would return 'Andreas', 'Andrea', and 'Andres'.
       */
      SortedMap<K, V> prefixMap(K prefix);
  }
  