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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.java.util.common.collect;


import com.google.common.base.Preconditions;
import com.google.common.collect.Iterators;

import javax.annotation.Nullable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

public class Utils
{
  public static  Map zipMap(K[] keys, V[] values)
  {
    Preconditions.checkArgument(values.length == keys.length,
                                "number of values[%s] different than number of keys[%s]",
                                values.length, keys.length
    );

    return zipMapPartial(keys, values);
  }

  public static  Map zipMapPartial(K[] keys, V[] values)
  {
    Preconditions.checkArgument(values.length <= keys.length,
                                "number of values[%s] exceeds number of keys[%s]",
                                values.length, keys.length
    );

    Map retVal = new LinkedHashMap<>();

    for (int i = 0; i < values.length; ++i) {
      retVal.put(keys[i], values[i]);
    }

    return retVal;
  }

  /**
   * Create a Map from iterables of keys and values. Will throw an exception if there are more keys than values,
   * or more values than keys.
   */
  public static  Map zipMap(Iterable keys, Iterable values)
  {
    Map retVal = new LinkedHashMap<>();

    Iterator keysIter = keys.iterator();
    Iterator valsIter = values.iterator();

    while (keysIter.hasNext()) {
      final K key = keysIter.next();

      Preconditions.checkArgument(valsIter.hasNext(),
                                  "number of values[%s] less than number of keys, broke on key[%s]",
                                  retVal.size(), key
      );

      retVal.put(key, valsIter.next());
    }

    Preconditions.checkArgument(!valsIter.hasNext(),
                                "number of values[%s] exceeds number of keys[%s]",
                                retVal.size() + Iterators.size(valsIter), retVal.size()
    );

    return retVal;
  }

  /**
   * Create a Map from iterables of keys and values. If there are more keys than values, or more values than keys,
   * the excess will be omitted.
   */
  public static  Map zipMapPartial(Iterable keys, Iterable values)
  {
    Map retVal = new LinkedHashMap<>();

    Iterator keysIter = keys.iterator();
    Iterator valsIter = values.iterator();

    while (keysIter.hasNext()) {
      final K key = keysIter.next();

      if (valsIter.hasNext()) {
        retVal.put(key, valsIter.next());
      } else {
        break;
      }

    }

    return retVal;
  }

  @SafeVarargs
  public static  List nullableListOf(@Nullable T... elements)
  {
    final List list;
    if (elements == null) {
      list = new ArrayList<>(1);
      list.add(null);
    } else {
      list = new ArrayList<>(elements.length);
      for (T element : elements) {
        list.add(element);
      }
    }
    return list;
  }
}