/*
 * 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.streaming.tests;

import org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;
import org.apache.flink.streaming.tests.verify.TtlStateVerifier;

import java.util.Map;
import java.util.Random;
import java.util.stream.Collectors;

/**
 * Source of randomly generated keyed state updates.
 *
 * <p>Internal loop generates {@code sleepAfterElements} state updates
 * for each verifier from {@link TtlStateVerifier#VERIFIERS} using {@link TtlStateVerifier#generateRandomUpdate}
 * and waits for {@code sleepTime} to continue generation.
 */
class TtlStateUpdateSource extends RichParallelSourceFunction<TtlStateUpdate> {

	private static final long serialVersionUID = 1L;

	private final int maxKey;
	private final long sleepAfterElements;
	private final long sleepTime;

	/** Flag that determines if this source is running, i.e. generating events. */
	private volatile boolean running = true;

	TtlStateUpdateSource(int maxKey, long sleepAfterElements, long sleepTime) {
		this.maxKey = maxKey;
		this.sleepAfterElements = sleepAfterElements;
		this.sleepTime = sleepTime;
	}

	@Override
	public void run(SourceContext<TtlStateUpdate> ctx) throws Exception {
		Random random = new Random();
		long elementsBeforeSleep = sleepAfterElements;
		while (running) {
			for (int i = 0; i < sleepAfterElements; i++) {
				synchronized (ctx.getCheckpointLock()) {
					Map<String, Object> updates = TtlStateVerifier.VERIFIERS.stream()
						.collect(Collectors.toMap(TtlStateVerifier::getId, TtlStateVerifier::generateRandomUpdate));
					ctx.collect(new TtlStateUpdate(random.nextInt(maxKey), updates));
				}
			}

			if (sleepTime > 0) {
				if (elementsBeforeSleep == 1) {
					elementsBeforeSleep = sleepAfterElements;
					long rnd = sleepTime < Integer.MAX_VALUE ? random.nextInt((int) sleepTime) : 0L;
					Thread.sleep(rnd + sleepTime);
				} else if (elementsBeforeSleep > 1) {
					--elementsBeforeSleep;
				}
			}
		}
	}

	@Override
	public void cancel() {
		running = false;
	}
}