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OptaPlanner solves planning problems. This lightweight, embeddable planning engine implements powerful and scalable algorithms to optimize business resource scheduling and planning. This module contains the examples which demonstrate how to use it in a normal Java application.

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/*
 * Copyright 2020 Red Hat, Inc. and/or its affiliates.
 *
 * 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 org.optaplanner.examples.scrabble.optional.score;

import org.optaplanner.core.api.score.buildin.hardmediumsoft.HardMediumSoftScore;
import org.optaplanner.core.api.score.stream.Constraint;
import org.optaplanner.core.api.score.stream.ConstraintCollectors;
import org.optaplanner.core.api.score.stream.ConstraintFactory;
import org.optaplanner.core.api.score.stream.ConstraintProvider;
import org.optaplanner.core.api.score.stream.Joiners;
import org.optaplanner.examples.scrabble.domain.ScrabbleCell;
import org.optaplanner.examples.scrabble.domain.ScrabbleWordAssignment;
import org.optaplanner.examples.scrabble.domain.ScrabbleWordDirection;

public class ScrabbleConstraintProvider implements ConstraintProvider {

    @Override
    public Constraint[] defineConstraints(ConstraintFactory constraintFactory) {
        return new Constraint[] {
                characterConflict(constraintFactory),
                noParallelHorizontalNeighbours(constraintFactory),
                noParallelVerticalNeighbours(constraintFactory),
                outOfGrid(constraintFactory),
                maximizeMergesPerWord(constraintFactory),
                pullToCenter(constraintFactory)
        };
    }

    private Constraint characterConflict(ConstraintFactory cf) {
        return cf.from(ScrabbleCell.class)
                .filter(sc -> sc.getCharacterSet().size() >= 2)
                .penalize("Character conflict", HardMediumSoftScore.ONE_HARD, sc -> sc.getCharacterSet().size() - 1);
    }

    private Constraint noParallelHorizontalNeighbours(ConstraintFactory cf) {
        return cf.from(ScrabbleCell.class).filter(sc -> sc.hasWordSet(ScrabbleWordDirection.HORIZONTAL))
                .ifExists(ScrabbleCell.class,
                        Joiners.equal(ScrabbleCell::getX), Joiners.equal(ScrabbleCell::getY, c -> c.getY() + 1),
                        Joiners.filtering((first, second) -> second.hasWordSet(ScrabbleWordDirection.HORIZONTAL)))
                .penalize("No parallel horizontal neighbours", HardMediumSoftScore.ONE_HARD);
    }

    private Constraint noParallelVerticalNeighbours(ConstraintFactory cf) {
        return cf.from(ScrabbleCell.class).filter(sc -> sc.hasWordSet(ScrabbleWordDirection.VERTICAL))
                .ifExists(ScrabbleCell.class,
                        Joiners.equal(ScrabbleCell::getY), Joiners.equal(ScrabbleCell::getX, c -> c.getX() + 1),
                        Joiners.filtering((first, second) -> second.hasWordSet(ScrabbleWordDirection.VERTICAL)))
                .penalize("No parallel vertical neighbours", HardMediumSoftScore.ONE_HARD);
    }

    private Constraint outOfGrid(ConstraintFactory cf) {
        return cf.from(ScrabbleWordAssignment.class)
                .filter(ScrabbleWordAssignment::isOutOfGrid)
                .penalize("Out of grid", HardMediumSoftScore.ONE_HARD, swa -> swa.getWord().length());
    }

    private Constraint maximizeMergesPerWord(ConstraintFactory cf) {
        return cf.from(ScrabbleWordAssignment.class)
                .join(ScrabbleCell.class, Joiners.filtering((swa, sc) -> sc.getWordSet().contains(swa) && sc.hasMerge()))
                .groupBy((swa, sc) -> swa.getId(), ConstraintCollectors.countBi())
                .reward("Maximize merges per word", HardMediumSoftScore.ONE_MEDIUM, (id, count) -> count * count);
    }

    private Constraint pullToCenter(ConstraintFactory cf) {
        return cf.from(ScrabbleWordAssignment.class)
                .penalize("Pull to the center", HardMediumSoftScore.ONE_SOFT, ScrabbleWordAssignment::getDistanceToCenter);
    }
}