/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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.giraph.types.ops.collections.array;
  
  import java.util.NoSuchElementException;
  
  import org.apache.giraph.function.Consumer;
  import org.apache.giraph.function.Predicate;
  import org.apache.giraph.types.ops.collections.ResettableIterator;
  
  /**
   * Private utilities class
   *
   * (needed since Java 7 has no default methods on interfaces,
   * and we need to extend appropriate fastutil classes)
   */
  class WArrayListPrivateUtils {
    /** Hide constructor */
    private WArrayListPrivateUtils() { }
  
    /**
     * Fast iterator over collection objects, which doesn't allocate new
     * element for each returned element, and can be iterated multiple times
     * using reset().
     *
     * Object returned by next() is only valid until next() is called again,
     * because it is reused.
     *
     * @param list Collection to iterate over
     * @param iterationValue reusable iteration value
     * @return RessettableIterator
     * @param <T> Element type
     */
    static <T> ResettableIterator<T> fastIterator(
        final WArrayList<T> list, final T iterationValue) {
      return new ResettableIterator<T>() {
        private int pos;
  
        @Override
        public boolean hasNext() {
          return pos < list.size();
        }
  
        @Override
        public T next() {
          if (!hasNext()) {
            throw new NoSuchElementException();
          }
          list.getIntoW(pos, iterationValue);
          pos++;
          return iterationValue;
        }
  
        @Override
        public void reset() {
          pos = 0;
        }
  
        @Override
        public void remove() {
          throw new UnsupportedOperationException();
        }
      };
    }
  
    /**
     * Traverse all elements of the collection, calling given function on each
     * element. Passed values are valid only during the call to the passed
     * function, so data needs to be consumed during the function.
     *
     * @param list Collection to iterate over
     * @param f Function to call on each element.
     * @param iterationValue reusable iteration value
     * @param <T> Element type
     */
    static <T> void fastForEach(
        WArrayList<T> list, Consumer<T> f, T iterationValue) {
      for (int i = 0; i < list.size(); ++i) {
        list.getIntoW(i, iterationValue);
        f.apply(iterationValue);
      }
    }
  
    /**
    * Traverse all elements of the collection, calling given function on each
    * element, or until predicate returns false.
    * Passed values are valid only during the call to the passed
    * function, so data needs to be consumed during the function.
    *
    * @param list Collection to iterate over
    * @param f Function to call on each element.
    * @param iterationValue reusable iteration value
    * @return true if the predicate returned true for all elements,
    *    false if it returned false for some element.
    * @param <T> Element type
    */
   static <T> boolean fastForEachWhile(
       WArrayList<T> list, Predicate<T> f, T iterationValue) {
     for (int i = 0; i < list.size(); ++i) {
       list.getIntoW(i, iterationValue);
       if (!f.apply(iterationValue)) {
         return false;
       }
     }
     return true;
   }
 }