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package org.egothor.stemmer;

/**
 * Defines the subtree reduction strategy applied during trie compilation.
 *
 * <p>
 * All reduction modes operate on the full subtree semantics, not only on the
 * local content of a single node. This is important because trie values may be
 * stored on both internal nodes and leaf nodes.
 */
@SuppressWarnings("PMD.LongVariable")
public enum ReductionMode {

    /**
     * Merges subtrees whose {@code getAll()} results are equivalent for every
     * reachable key suffix and whose local result ordering is the same.
     *
     * <p>
     * This mode ignores absolute frequencies when comparing subtree signatures, but
     * preserves the value order returned by {@code getAll()}.
     */
    MERGE_SUBTREES_WITH_EQUIVALENT_RANKED_GET_ALL_RESULTS,

    /**
     * Merges subtrees whose {@code getAll()} results are equivalent for every
     * reachable key suffix, regardless of the local ordering of values.
     *
     * <p>
     * This mode ignores both absolute frequencies and local result ordering when
     * comparing subtree signatures.
     */
    MERGE_SUBTREES_WITH_EQUIVALENT_UNORDERED_GET_ALL_RESULTS,

    /**
     * Merges subtrees whose preferred {@code get()} results are equivalent for
     * every reachable key suffix, provided that the locally dominant winner
     * satisfies the configured dominance constraints.
     *
     * <p>
     * If a node does not satisfy the dominance constraints, the implementation
     * falls back to ranked {@code getAll()} semantics for that node in order to
     * avoid unsafe over-reduction.
     */
    MERGE_SUBTREES_WITH_EQUIVALENT_DOMINANT_GET_RESULTS
}
