ReductionSettings.java

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package org.egothor.stemmer;

import java.util.Objects;

/**
 * Immutable reduction configuration used by {@link FrequencyTrie.Builder}.
 *
 * <p>
 * The settings influence how mutable trie nodes are merged into canonical
 * read-only nodes during compilation.
 * 
 * @param reductionMode                 reduction mode
 * @param dominantWinnerMinPercent      minimum dominant winner percentage
 * @param dominantWinnerOverSecondRatio minimum winner-over-second ratio
 */
@SuppressWarnings("PMD.LongVariable")
public record ReductionSettings(ReductionMode reductionMode, int dominantWinnerMinPercent,
        int dominantWinnerOverSecondRatio) {

    /**
     * Default minimum dominant winner percentage.
     */
    public static final int DEFAULT_DOMINANT_WINNER_MIN_PERCENT = 75;

    /**
     * Default minimum winner-over-second ratio.
     */
    public static final int DEFAULT_DOMINANT_WINNER_OVER_SECOND_RATIO = 3;

    /**
     * Creates a new instance.
     *
     * @param reductionMode                 reduction mode
     * @param dominantWinnerMinPercent      minimum dominant winner percentage in
     *                                      the inclusive range {@code 1..100}
     * @param dominantWinnerOverSecondRatio minimum winner-over-second ratio, must
     *                                      be at least {@code 1}
     * @throws NullPointerException     if {@code reductionMode} is {@code null}
     * @throws IllegalArgumentException if any numeric value is outside the valid
     *                                  range
     */
    public ReductionSettings(final ReductionMode reductionMode, final int dominantWinnerMinPercent,
            final int dominantWinnerOverSecondRatio) {
        this.reductionMode = Objects.requireNonNull(reductionMode, "reductionMode");
        if (dominantWinnerMinPercent < 1 || dominantWinnerMinPercent > 100) {
            throw new IllegalArgumentException("dominantWinnerMinPercent must be in range 1..100.");
        }
        if (dominantWinnerOverSecondRatio < 1) { // NOPMD
            throw new IllegalArgumentException("dominantWinnerOverSecondRatio must be at least 1.");
        }
        this.dominantWinnerMinPercent = dominantWinnerMinPercent;
        this.dominantWinnerOverSecondRatio = dominantWinnerOverSecondRatio;
    }

    /**
     * Creates settings with default dominance thresholds.
     *
     * @param reductionMode reduction mode
     * @return new settings instance
     * @throws NullPointerException if {@code reductionMode} is {@code null}
     */
    public static ReductionSettings withDefaults(final ReductionMode reductionMode) {
        return new ReductionSettings(reductionMode, DEFAULT_DOMINANT_WINNER_MIN_PERCENT,
                DEFAULT_DOMINANT_WINNER_OVER_SECOND_RATIO);
    }
}