/*
 * 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.flink.test.windowing.sessionwindows;

import java.util.Collection;
import java.util.Random;

public class LongRandomGenerator extends Random {

	static final long serialVersionUID = 32523525277L;

	public LongRandomGenerator(long seed) {
		super(seed);
	}

	/**
	 * @param minInclusive lower bound for the returned value (inclusive)
	 * @param maxExclusive upper bound for the returned value (exclusive)
	 * @return random long between the provided min (inclusive) and max (exclusive)
	 */
	public long randomLongBetween(long minInclusive, long maxExclusive) {
		if (maxExclusive <= minInclusive) {
			throw new IllegalArgumentException(String.format("Error: min (found %s) must be < than max (found %s)!",
					minInclusive, maxExclusive));
		}
		long bits;
		long generatedValue;
		long delta = maxExclusive - minInclusive;
		do {
			bits = (nextLong() << 1) >>> 1;
			generatedValue = bits % delta;
		} while (bits - generatedValue + (delta - 1) < 0L);
		return minInclusive + generatedValue;
	}

	/**
	 * @param collection collection to chose from
	 * @return selects a valid random index from the collection's range of indices
	 */
	public int choseRandomIndex(Collection<?> collection) {
		return nextInt(collection.size());
	}

	/**
	 * @return a randomly chosen element from collection
	 */
	public <T> T choseRandomElement(Collection<T> collection) {
		int choice = choseRandomIndex(collection);
		for (T key : collection) {
			if (choice == 0) {
				return key;
			}
			--choice;
		}
		return null;
	}
}