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/*
 * 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.pragmaticminds.crunch.api.trigger.strategy;

import org.pragmaticminds.crunch.api.records.MRecord;
import org.pragmaticminds.crunch.api.trigger.comparator.SerializableFunction;
import org.pragmaticminds.crunch.api.trigger.comparator.SerializableResultFunction;

import java.util.HashSet;
import java.util.Set;

/**
 * Wraps the {@link TriggerStrategy} so that it can be implemented with lambda definitions.
 *
 * @author Erwin Wagasow
 * Created by Erwin Wagasow on 27.09.2018
 */
public class LambdaTriggerStrategy implements TriggerStrategy {

    private SerializableFunction isToBeTriggeredLambda;
    private SerializableResultFunction> getChannelIdentifiersLambda;

    /**
     * Main constructor that takes the lambdas which are defining the processing.
     *
     * @param isToBeTriggeredLambda       determines whether to be triggered.
     * @param getChannelIdentifiersLambda collect all channel identifiers that are being used.
     */
    public LambdaTriggerStrategy(
            SerializableFunction isToBeTriggeredLambda,
            SerializableResultFunction> getChannelIdentifiersLambda) {
        this.isToBeTriggeredLambda = isToBeTriggeredLambda;
        this.getChannelIdentifiersLambda = getChannelIdentifiersLambda;
    }

    /**
     * Decides if the event is to be triggered by the decision base typed value
     *
     * @param values contains the indicator if processing is to be triggered
     * @return true if triggering was positive
     */
    @Override
    public boolean isToBeTriggered(MRecord values) {
        return isToBeTriggeredLambda.apply(values);
    }

    /**
     * Returns all channel identifiers which are necessary for the function to do its job.
     * It is not allowed to return null, an empty set can be returned (but why should??).
     *
     * @return a {@link Set} all channel identifiers that are needed by the Evaluation Function.
     */
    @Override
    public Set getChannelIdentifiers() {
        return getChannelIdentifiersLambda.get();
    }
}