/*
 * 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.jmeter.timers.poissonarrivals;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class PreciseThroughputTimerTest {
	private static final Logger LOG = LoggerFactory.getLogger(PreciseThroughputTimerTest.class);

	@Test
	public void testTimer1() throws Exception {
		ConstantPoissonProcessGenerator gen = getConstantPoissonProcessGenerator(2, 5, 42L);
		gen.generateNext();
		assertEquals(0.6501751901910952, gen.next(), 0.01);
		assertEquals(1.2249545461599474, gen.next(), 0.01);
		assertEquals(1.409559315928937, gen.next(), 0.01);
		assertEquals(1.5717866281130652, gen.next(), 0.01);
		assertEquals(2.1194190047658874, gen.next(), 0.01);
		assertEquals(3.2878637366551384, gen.next(), 0.01);
		assertEquals(3.517916456559849, gen.next(), 0.01);
		assertEquals(3.679224444929692, gen.next(), 0.01);
		assertEquals(3.9907119513763165, gen.next(), 0.01);
		assertEquals(4.754414649148714, gen.next(), 0.01);
		// ^^ 10 samples for 5 seconds
		assertEquals(6.013095167372755, gen.next(), 0.01);
	}

	@Test
	public void testExactNumberOfSamples() throws Exception {
		java.util.Random rnd = new java.util.Random();
		long seed = rnd.nextLong();
		// Log seed, so the test can be reproduced in case of failure
		LOG.info("testExactNumberOfSamples is using seed " + seed);
		rnd.setSeed(seed);

		int testDuration = 5;
		for (int i = 0; i < 1000; i++) {
			ConstantPoissonProcessGenerator gen = getConstantPoissonProcessGenerator(2, testDuration, rnd.nextLong());
			gen.generateNext();
			for (int j = 0; j < 10; j++) {
				double next = gen.next();
				assertTrue("Delay #" + j + " (0-based) exceeds " + testDuration + " seconds", next < 5.0);
			}
		}
	}

	protected ConstantPoissonProcessGenerator getConstantPoissonProcessGenerator(
			final double throughput, final int duration, long seed) {
		return new ConstantPoissonProcessGenerator(
				new ThroughputProvider() {
					@Override
					public double getThroughput() {
						return throughput; // samples per second
					}
				},
				1,
				0,
				new DurationProvider() {
					@Override
					public long getDuration() {
						return duration; // "expected" test duration: 3 seconds
					}
				},
				10000,
				0.1,
				seed, // Seed
				false
		);
	}

}
