/*
 * Copyright 2012-2017 the original author or 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 org.springframework.boot.actuate.metrics.buffer;

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Collection;
import java.util.HashSet;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.atomic.DoubleAdder;
import java.util.concurrent.atomic.LongAdder;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.regex.Pattern;

import org.junit.AfterClass;
import org.junit.BeforeClass;
import org.junit.experimental.theories.DataPoints;
import org.junit.experimental.theories.Theories;
import org.junit.experimental.theories.Theory;
import org.junit.runner.RunWith;

import org.springframework.boot.actuate.metrics.GaugeService;
import org.springframework.boot.actuate.metrics.Metric;
import org.springframework.util.StopWatch;

import static org.assertj.core.api.Assertions.assertThat;

/**
 * Speed tests for {@link BufferGaugeService}.
 *
 * @author Dave Syer
 */
@RunWith(Theories.class)
public class BufferGaugeServiceSpeedTests {

	@DataPoints
	public static String[] values = new String[10];

	public static String[] names = new String[] { "foo", "bar", "spam", "bucket" };

	public static String[] sample = new String[1000];

	private GaugeBuffers gauges = new GaugeBuffers();

	private GaugeService service = new BufferGaugeService(this.gauges);

	private BufferMetricReader reader = new BufferMetricReader(new CounterBuffers(),
			this.gauges);

	private static int threadCount = 2;

	private static final int number = Boolean.getBoolean("performance.test") ? 10000000
			: 1000000;

	private static StopWatch watch = new StopWatch("count");

	private static int count;

	private static PrintWriter err;

	@BeforeClass
	public static void prime() throws FileNotFoundException {
		err = new NullPrintWriter();
		final Random random = new Random();
		for (int i = 0; i < 1000; i++) {
			sample[i] = names[random.nextInt(names.length)];
		}
	}

	@AfterClass
	public static void washup() {
		System.err.println(watch);
	}

	@Theory
	public void raw(String input) throws Exception {
		iterate("writeRaw");
		double rate = number / watch.getLastTaskTimeMillis() * 1000;
		System.err.println("Rate(" + count + ")=" + rate + ", " + watch);
		watch.start("readRaw" + count);
		for (String name : names) {
			this.gauges.forEach(Pattern.compile(name).asPredicate(),
					new BiConsumer<String, GaugeBuffer>() {
						@Override
						public void accept(String name, GaugeBuffer value) {
							err.println(name + "=" + value);
						}
					});
		}
		final DoubleAdder total = new DoubleAdder();
		this.gauges.forEach(Pattern.compile(".*").asPredicate(),
				new BiConsumer<String, GaugeBuffer>() {
					@Override
					public void accept(String name, GaugeBuffer value) {
						total.add(value.getValue());
					}
				});
		watch.stop();
		System.err.println("Read(" + count + ")=" + watch.getLastTaskTimeMillis() + "ms");
		assertThat(number * threadCount < total.longValue()).isTrue();
	}

	@Theory
	public void reader(String input) throws Exception {
		iterate("writeReader");
		double rate = number / watch.getLastTaskTimeMillis() * 1000;
		System.err.println("Rate(" + count + ")=" + rate + ", " + watch);
		watch.start("readReader" + count);
		this.reader.findAll().forEach(new Consumer<Metric<?>>() {
			@Override
			public void accept(Metric<?> metric) {
				err.println(metric);
			}
		});
		final LongAdder total = new LongAdder();
		this.reader.findAll().forEach(new Consumer<Metric<?>>() {
			@Override
			public void accept(Metric<?> value) {
				total.add(value.getValue().intValue());
			}
		});
		watch.stop();
		System.err.println("Read(" + count + ")=" + watch.getLastTaskTimeMillis() + "ms");
		assertThat(0 < total.longValue()).isTrue();
	}

	private void iterate(String taskName) throws Exception {
		watch.start(taskName + count++);
		ExecutorService pool = Executors.newFixedThreadPool(threadCount);
		Runnable task = new Runnable() {
			@Override
			public void run() {
				for (int i = 0; i < number; i++) {
					String name = sample[i % sample.length];
					BufferGaugeServiceSpeedTests.this.service.submit(name, count + i);
				}
			}
		};
		Collection<Future<?>> futures = new HashSet<>();
		for (int i = 0; i < threadCount; i++) {
			futures.add(pool.submit(task));
		}
		for (Future<?> future : futures) {
			future.get();
		}
		watch.stop();
	}

}
