/*
 * 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.wayang.core.mapping;

import java.util.Map;
import java.util.function.BiFunction;
import org.apache.commons.lang3.Validate;
import org.apache.wayang.core.plan.wayangplan.ActualOperator;
import org.apache.wayang.core.plan.wayangplan.InputSlot;
import org.apache.wayang.core.plan.wayangplan.Operator;
import org.apache.wayang.core.plan.wayangplan.OperatorAlternative;
import org.apache.wayang.core.plan.wayangplan.OperatorBase;
import org.apache.wayang.core.plan.wayangplan.OutputSlot;
import org.apache.wayang.core.plan.wayangplan.Subplan;

/**
 * This factory takes an {@link SubplanMatch} and derives a replacement {@link Subplan} from it.
 */
public abstract class ReplacementSubplanFactory {

    public Operator createReplacementSubplan(SubplanMatch subplanMatch, int epoch) {
        final Operator replacementSubplan = this.translate(subplanMatch, epoch);
        this.checkSanity(subplanMatch, replacementSubplan);
        this.copyNames(subplanMatch, replacementSubplan);
        return replacementSubplan;
    }

    protected void copyNames(SubplanMatch subplanMatch, Operator replacementSubplan) {
        if (subplanMatch.getOperatorMatches().size() == 1) {
            final OperatorMatch operatorMatch = subplanMatch.getOperatorMatches().values().stream().findAny().get();
            final Operator operator = operatorMatch.getOperator();
            String operatorName;
            if ((operatorName = operator.getName()) != null) {
                this.setNameTo(operatorName, replacementSubplan);
            }
        }
    }

    private void setNameTo(String operatorName, Operator targetOperator) {
        if (targetOperator instanceof Subplan || targetOperator instanceof OperatorAlternative) {
            // Minor: Propagate names to subplans.
        } else if (targetOperator instanceof ActualOperator && targetOperator instanceof OperatorBase) {
            final OperatorBase operatorBase = (OperatorBase) targetOperator;
            if (operatorBase.getName() == null) {
                operatorBase.setName(operatorName);
            }
        }
    }


    protected void checkSanity(SubplanMatch subplanMatch, Operator replacementSubplan) {
        if (replacementSubplan.getNumInputs() != subplanMatch.getInputMatch().getOperator().getNumInputs()) {
            throw new IllegalStateException("Incorrect number of inputs in the replacement subplan.");
        }
        if (replacementSubplan.getNumOutputs() != subplanMatch.getOutputMatch().getOperator().getNumOutputs()) {
            throw new IllegalStateException("Incorrect number of outputs in the replacement subplan.");
        }
    }

    protected abstract Operator translate(SubplanMatch subplanMatch, int epoch);

    /**
     * Implementation of the {@link ReplacementSubplanFactory}
     * <ul>
     * <li>that replaces exactly one {@link Operator} with exactly one {@link Operator},</li>
     * <li>where both have the exact same {@link InputSlot}s and {@link OutputSlot} in the exact same order.</li>
     * </ul>
     */
    public static class OfSingleOperators<MatchedOperator extends Operator> extends ReplacementSubplanFactory {

        private final BiFunction<MatchedOperator, Integer, Operator> replacementFactory;

        /**
         * Creates a new instance.
         *
         * @param replacementFactory factory for the replacement {@link Operator}s
         */
        public OfSingleOperators(BiFunction<MatchedOperator, Integer, Operator> replacementFactory) {
            this.replacementFactory = replacementFactory;
        }

        @Override
        protected Operator translate(SubplanMatch subplanMatch, int epoch) {
            // Extract the single matched Operator.
            final Map<String, OperatorMatch> operatorMatches = subplanMatch.getOperatorMatches();
            Validate.isTrue(operatorMatches.size() == 1);
            final OperatorMatch operatorMatch = operatorMatches.values().stream().findFirst().get();
            final Operator matchedOperator = operatorMatch.getOperator();

            // Create a replacement Operator and align the InputSlots.
            final Operator replacementOperator = this.replacementFactory.apply((MatchedOperator) matchedOperator, epoch);
            for (int inputIndex = matchedOperator.getNumRegularInputs(); inputIndex < matchedOperator.getNumInputs(); inputIndex++) {
                final InputSlot<?> broadcastInput = matchedOperator.getInput(inputIndex);
                Validate.isTrue(broadcastInput.isBroadcast());
                replacementOperator.addBroadcastInput(broadcastInput.copyFor(replacementOperator));
            }

            return replacementOperator;
        }
    }

}