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/*
 *  Copyright 2018 Data Artisans GmbH
 *
 *  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 com.dataartisans.streamingledger.examples.simpletrade.generator;

import org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;

import java.util.SplittableRandom;

import static org.apache.flink.util.Preconditions.checkArgument;

/**
 * A simple random data generator with data rate throttling logic.
 */
public abstract class BaseGenerator extends RichParallelSourceFunction {

    private static final long serialVersionUID = 1L;

    private final int maxRecordsPerSecond;

    private volatile boolean running = true;

    BaseGenerator(int maxRecordsPerSecond) {
        checkArgument(maxRecordsPerSecond == -1 || maxRecordsPerSecond > 0,
                "maxRecordsPerSecond must be positive or -1 (infinite)");
        this.maxRecordsPerSecond = maxRecordsPerSecond;
    }

    @Override
    public final void run(SourceContext ctx) throws Exception {
        final int numberOfParallelSubtasks = getRuntimeContext().getNumberOfParallelSubtasks();
        final Throttler throttler = new Throttler(maxRecordsPerSecond, numberOfParallelSubtasks);
        final SplittableRandom rnd = new SplittableRandom();

        while (running) {
            T event = randomEvent(rnd);
            ctx.collect(event);
            throttler.throttle();
        }
    }

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

    abstract T randomEvent(SplittableRandom rnd);

}