/*
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.edgent.samples.topology;

import java.util.Random;
import java.util.concurrent.TimeUnit;

import org.apache.edgent.providers.direct.DirectProvider;
import org.apache.edgent.topology.TStream;
import org.apache.edgent.topology.Topology;

/**
 * Periodic polling of source data.
 *
 */
public class PeriodicSource {
    /**
     * Shows polling a data source to periodically obtain a value.
     * Polls a random number generator for a new value every second
     * and then prints out the raw value and a filtered and transformed stream.
     * @param args command arguments
     * @throws Exception on failure
     */
    public static void main(String[] args) throws Exception {

        DirectProvider tp = new DirectProvider();

        Topology t = tp.newTopology("PeriodicSource");

        // Since this is the Direct provider the graph can access
        // objects created while the topology is being defined
        // (in this case the Random object r).
        Random r = new Random();
        TStream<Double> gaussian = t.poll(() -> r.nextGaussian(), 1, TimeUnit.SECONDS);

        // Peek at the value on the Stream printing it to System.out
        gaussian = gaussian.peek(g -> System.out.println("R:" + g));

        // A filter
        gaussian = gaussian.filter(g -> g > 0.5);

        // A transformation
        TStream<String> gs = gaussian.map(g -> "G:" + g + ":");
        gs.print();

        tp.submit(t);
    }
}