/*
    * Copyright (C) 2007 The Guava Authors
    *
    * 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 com.google.common.collect;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.io.Serializable;
  import java.util.Iterator;
  
  import javax.annotation.Nullable;
  
  /**
   * An ordering which sorts iterables by comparing corresponding elements
   * pairwise.
   */
  @GwtCompatible(serializable = true)
  final class LexicographicalOrdering<T>
      extends Ordering<Iterable<T>> implements Serializable {
    final Ordering<? super T> elementOrder;
  
    LexicographicalOrdering(Ordering<? super T> elementOrder) {
      this.elementOrder = elementOrder;
    }
  
    @Override public int compare(
        Iterable<T> leftIterable, Iterable<T> rightIterable) {
      Iterator<T> left = leftIterable.iterator();
      Iterator<T> right = rightIterable.iterator();
      while (left.hasNext()) {
        if (!right.hasNext()) {
          return LEFT_IS_GREATER; // because it's longer
        }
        int result = elementOrder.compare(left.next(), right.next());
        if (result != 0) {
          return result;
        }
      }
      if (right.hasNext()) {
        return RIGHT_IS_GREATER; // because it's longer
      }
      return 0;
    }
  
    @Override public boolean equals(@Nullable Object object) {
      if (object == this) {
        return true;
      }
      if (object instanceof LexicographicalOrdering) {
        LexicographicalOrdering<?> that = (LexicographicalOrdering<?>) object;
        return this.elementOrder.equals(that.elementOrder);
      }
      return false;
    }
  
    @Override public int hashCode() {
      return elementOrder.hashCode() ^ 2075626741; // meaningless
    }
  
    @Override public String toString() {
      return elementOrder + ".lexicographical()";
    }
  
    private static final long serialVersionUID = 0;
  }