package org.optaplanner.test.impl.score.stream;

import static java.util.Objects.requireNonNull;

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.stream.Collectors;

import org.optaplanner.constraint.streams.common.AbstractConstraint;
import org.optaplanner.constraint.streams.common.AbstractConstraintStreamScoreDirectorFactory;
import org.optaplanner.constraint.streams.common.ScoreImpactType;
import org.optaplanner.core.api.score.Score;
import org.optaplanner.core.api.score.constraint.ConstraintMatchTotal;
import org.optaplanner.core.api.score.constraint.Indictment;
import org.optaplanner.core.impl.score.DefaultScoreExplanation;
import org.optaplanner.core.impl.score.definition.ScoreDefinition;
import org.optaplanner.test.api.score.stream.SingleConstraintAssertion;

public final class DefaultSingleConstraintAssertion<Solution_, Score_ extends Score<Score_>>
        implements SingleConstraintAssertion {

    private final AbstractConstraint<Solution_, ?, ?> constraint;
    private final ScoreDefinition<Score_> scoreDefinition;
    private final Score_ score;
    private final Collection<ConstraintMatchTotal<Score_>> constraintMatchTotalCollection;
    private final Collection<Indictment<Score_>> indictmentCollection;

    DefaultSingleConstraintAssertion(AbstractConstraintStreamScoreDirectorFactory<Solution_, Score_> scoreDirectorFactory,
            Score_ score, Map<String, ConstraintMatchTotal<Score_>> constraintMatchTotalMap,
            Map<Object, Indictment<Score_>> indictmentMap) {
        this.constraint = (AbstractConstraint<Solution_, ?, ?>) scoreDirectorFactory.getConstraints()[0];
        this.scoreDefinition = scoreDirectorFactory.getScoreDefinition();
        this.score = requireNonNull(score);
        this.constraintMatchTotalCollection = new ArrayList<>(requireNonNull(constraintMatchTotalMap).values());
        this.indictmentCollection = new ArrayList<>(requireNonNull(indictmentMap).values());
    }

    @Override
    public void penalizesBy(int matchWeightTotal, String message) {
        validateMatchWeighTotal(matchWeightTotal);
        assertImpact(ScoreImpactType.PENALTY, matchWeightTotal, message);
    }

    @Override
    public void penalizesBy(long matchWeightTotal, String message) {
        validateMatchWeighTotal(matchWeightTotal);
        assertImpact(ScoreImpactType.PENALTY, matchWeightTotal, message);
    }

    @Override
    public void penalizesBy(BigDecimal matchWeightTotal, String message) {
        validateMatchWeighTotal(matchWeightTotal);
        assertImpact(ScoreImpactType.PENALTY, matchWeightTotal, message);
    }

    @Override
    public void penalizes(long times, String message) {
        assertMatchCount(ScoreImpactType.PENALTY, times, message);
    }

    @Override
    public void penalizes(String message) {
        assertMatch(ScoreImpactType.PENALTY, message);
    }

    @Override
    public void rewardsWith(int matchWeightTotal, String message) {
        validateMatchWeighTotal(matchWeightTotal);
        assertImpact(ScoreImpactType.REWARD, matchWeightTotal, message);
    }

    @Override
    public void rewardsWith(long matchWeightTotal, String message) {
        validateMatchWeighTotal(matchWeightTotal);
        assertImpact(ScoreImpactType.REWARD, matchWeightTotal, message);
    }

    @Override
    public void rewardsWith(BigDecimal matchWeightTotal, String message) {
        validateMatchWeighTotal(matchWeightTotal);
        assertImpact(ScoreImpactType.REWARD, matchWeightTotal, message);
    }

    @Override
    public void rewards(long times, String message) {
        assertMatchCount(ScoreImpactType.REWARD, times, message);
    }

    @Override
    public void rewards(String message) {
        assertMatch(ScoreImpactType.REWARD, message);
    }

    private void validateMatchWeighTotal(Number matchWeightTotal) {
        if (matchWeightTotal.doubleValue() < 0) {
            throw new IllegalArgumentException("The matchWeightTotal (" + matchWeightTotal + ") must be positive.");
        }
    }

    private void assertImpact(ScoreImpactType scoreImpactType, Number matchWeightTotal, String message) {
        Number impact = deduceImpact();
        long longImpact = impact.longValue(); // Impact is always int or long, so this is safe.
        ScoreImpactType actualScoreImpactType = constraint.getScoreImpactType();
        if (actualScoreImpactType == ScoreImpactType.MIXED) {
            // Impact means we need to check for expected impact type and actual impact match.
            switch (scoreImpactType) {
                case REWARD:
                    if (matchWeightTotal.longValue() == -longImpact) {
                        return;
                    }
                    break;
                case PENALTY:
                    if (matchWeightTotal.longValue() == longImpact) {
                        return;
                    }
                    break;
            }
        } else if (actualScoreImpactType == scoreImpactType && matchWeightTotal.longValue() == longImpact) {
            // Reward and positive or penalty and negative means all is OK.
            return;
        }
        String constraintId = constraint.getConstraintId();
        String assertionMessage = buildAssertionErrorMessage(scoreImpactType, matchWeightTotal, actualScoreImpactType,
                impact, constraintId, message);
        throw new AssertionError(assertionMessage);
    }

    private Number deduceImpact() {
        Score_ zeroScore = scoreDefinition.getZeroScore();
        Number zero = zeroScore.toLevelNumbers()[0]; // Zero in the exact numeric type expected by the caller.
        if (constraintMatchTotalCollection.isEmpty()) {
            return zero;
        }
        // We do not know the matchWeight, so we need to deduce it.
        // Constraint matches give us a score, whose levels are in the form of (matchWeight * constraintWeight).
        // Here, we strip the constraintWeight.
        Score_ totalMatchWeightedScore = constraintMatchTotalCollection.stream()
                .map(matchScore -> scoreDefinition.divideBySanitizedDivisor(matchScore.getScore(),
                        matchScore.getConstraintWeight()))
                .reduce(zeroScore, Score::add);
        // Each level of the resulting score now has to be the same number, the matchWeight.
        // Except for where the number is zero.
        List<Number> matchWeightsFound = Arrays.stream(totalMatchWeightedScore.toLevelNumbers())
                .distinct()
                .filter(matchWeight -> !Objects.equals(matchWeight, zero))
                .collect(Collectors.toList());
        if (matchWeightsFound.isEmpty()) {
            return zero;
        } else if (matchWeightsFound.size() != 1) {
            throw new IllegalStateException("Impossible state: expecting at most one match weight," +
                    " but got matchWeightsFound (" + matchWeightsFound + ") instead.");
        }
        return matchWeightsFound.get(0);
    }

    private void assertMatchCount(ScoreImpactType scoreImpactType, long expectedMatchCount, String message) {
        long actualMatchCount = determineMatchCount(scoreImpactType);
        if (actualMatchCount == expectedMatchCount) {
            return;
        }
        String constraintId = constraint.getConstraintId();
        String assertionMessage =
                buildAssertionErrorMessage(scoreImpactType, expectedMatchCount, actualMatchCount, constraintId, message);
        throw new AssertionError(assertionMessage);
    }

    private void assertMatch(ScoreImpactType scoreImpactType, String message) {
        if (determineMatchCount(scoreImpactType) > 0) {
            return;
        }
        String constraintId = constraint.getConstraintId();
        String assertionMessage = buildAssertionErrorMessage(scoreImpactType, constraintId, message);
        throw new AssertionError(assertionMessage);
    }

    private long determineMatchCount(ScoreImpactType scoreImpactType) {
        if (constraintMatchTotalCollection.isEmpty()) {
            return 0;
        }
        ScoreImpactType actualImpactType = constraint.getScoreImpactType();

        if (actualImpactType != scoreImpactType && actualImpactType != ScoreImpactType.MIXED) {
            return 0;
        }
        Score_ zeroScore = scoreDefinition.getZeroScore();
        return constraintMatchTotalCollection.stream()
                .mapToLong(constraintMatchTotal -> {
                    if (actualImpactType == ScoreImpactType.MIXED) {
                        boolean isImpactPositive = constraintMatchTotal.getScore().compareTo(zeroScore) > 0;
                        boolean isImpactNegative = constraintMatchTotal.getScore().compareTo(zeroScore) < 0;
                        if (isImpactPositive && scoreImpactType == ScoreImpactType.PENALTY) {
                            return constraintMatchTotal.getConstraintMatchSet().size();
                        } else if (isImpactNegative && scoreImpactType == ScoreImpactType.REWARD) {
                            return constraintMatchTotal.getConstraintMatchSet().size();
                        } else {
                            return 0;
                        }
                    } else {
                        return constraintMatchTotal.getConstraintMatchSet().size();
                    }
                })
                .sum();
    }

    private String buildAssertionErrorMessage(ScoreImpactType expectedImpactType, Number expectedImpact,
            ScoreImpactType actualImpactType, Number actualImpact, String constraintId, String message) {
        String expectation = message != null ? message : "Broken expectation.";
        String preformattedMessage = "%s%n" +
                "%18s: %s%n" +
                "%18s: %s (%s)%n" +
                "%18s: %s (%s)%n%n" +
                "  %s";
        String expectedImpactLabel = "Expected " + getImpactTypeLabel(expectedImpactType);
        String actualImpactLabel = "Actual " + getImpactTypeLabel(actualImpactType);
        return String.format(preformattedMessage,
                expectation,
                "Constraint", constraintId,
                expectedImpactLabel, expectedImpact, expectedImpact.getClass(),
                actualImpactLabel, actualImpact, actualImpact.getClass(),
                DefaultScoreExplanation.explainScore(score, constraintMatchTotalCollection, indictmentCollection));
    }

    private String buildAssertionErrorMessage(ScoreImpactType impactType, long expectedTimes, long actualTimes,
            String constraintId, String message) {
        String expectation = message != null ? message : "Broken expectation.";
        String preformattedMessage = "%s%n" +
                "%18s: %s%n" +
                "%18s: %s time(s)%n" +
                "%18s: %s time(s)%n%n" +
                "  %s";
        String expectedImpactLabel = "Expected " + getImpactTypeLabel(impactType);
        String actualImpactLabel = "Actual " + getImpactTypeLabel(impactType);
        return String.format(preformattedMessage,
                expectation,
                "Constraint", constraintId,
                expectedImpactLabel, expectedTimes,
                actualImpactLabel, actualTimes,
                DefaultScoreExplanation.explainScore(score, constraintMatchTotalCollection, indictmentCollection));
    }

    private String buildAssertionErrorMessage(ScoreImpactType impactType, String constraintId, String message) {
        String expectation = message != null ? message : "Broken expectation.";
        String preformattedMessage = "%s%n" +
                "%18s: %s%n" +
                "%18s but there was none.%n%n" +
                "  %s";
        String expectedImpactLabel = "Expected " + getImpactTypeLabel(impactType);
        return String.format(preformattedMessage,
                expectation,
                "Constraint", constraintId,
                expectedImpactLabel,
                DefaultScoreExplanation.explainScore(score, constraintMatchTotalCollection, indictmentCollection));
    }

    private String getImpactTypeLabel(ScoreImpactType scoreImpactType) {
        if (scoreImpactType == ScoreImpactType.PENALTY) {
            return "penalty";
        } else if (scoreImpactType == ScoreImpactType.REWARD) {
            return "reward";
        } else { // Needs to work with null.
            return "impact";
        }
    }

}
