/*
 * 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.runtime.io.network.api.serialization.types;

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Random;

/**
 * Utility class to help serialization for testing.
 */
public final class Util {

	private static final long SEED = 64871654635745873L;

	private static Random random = new Random(SEED);

	public static SerializationTestType randomRecord(SerializationTestTypeFactory type) {
		return type.factory().getRandom(Util.random);
	}

	public static MockRecords randomRecords(final int numElements, final SerializationTestTypeFactory type) {

		return new MockRecords(numElements) {
			@Override
			protected SerializationTestType getRecord() {
				return type.factory().getRandom(Util.random);
			}
		};
	}

	public static MockRecords randomRecords(final int numElements) {

		return new MockRecords(numElements) {
			@Override
			protected SerializationTestType getRecord() {
				// select random test type factory
				SerializationTestTypeFactory[] types = SerializationTestTypeFactory.values();
				int i = Util.random.nextInt(types.length);

				return types[i].factory().getRandom(Util.random);
			}
		};
	}

	// -----------------------------------------------------------------------------------------------------------------
	public abstract static class MockRecords implements Iterable<SerializationTestType> {

		private int numRecords;

		public MockRecords(int numRecords) {
			this.numRecords = numRecords;
		}

		@Override
		public Iterator<SerializationTestType> iterator() {
			return new Iterator<SerializationTestType>() {
				@Override
				public boolean hasNext() {
					return numRecords > 0;
				}

				@Override
				public SerializationTestType next() {
					if (numRecords > 0) {
						numRecords--;

						return getRecord();
					}

					throw new NoSuchElementException();
				}

				@Override
				public void remove() {
					throw new UnsupportedOperationException();
				}
			};
		}

		abstract protected SerializationTestType getRecord();
	}

	/**
	 * No instantiation.
	 */
	private Util() {
		throw new RuntimeException();
	}
}