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package org.javimmutable.collections.array.trie32;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Holder;
import org.javimmutable.collections.JImmutableMap;
import org.javimmutable.collections.SplitableIterator;
import org.javimmutable.collections.common.MutableDelta;

/**
 * Interface for transformation objects that manage the leaf nodes in the hash table.
 * Implementations are free to use any class for their leaf nodes and manage them as needed.
 * NOTE: The transforms object is shared across all versions of a hash table so it MUST BE IMMUTABLE.
 * If the transforms object is not immutable it can cause the table to become
 * corrupted over time and/or make older versions of the table invalid.
 */
public interface Transforms
{
    /**
     * Take the current leaf object (if there is one) and produce a new one
     * (possibly the same) with the specified key and value.  If there is not currently
     * a leaf for this key in the array the Holder will be empty.  The result must be
     * a non-null leaf object with the specified value associated with the specified key.
     * If this key was not previously present the method must add 1 to the delta
     * so that the size of the array can be properly maintained.
     */
    T update(Holder leaf,
             K key,
             V value,
             MutableDelta delta);

    /**
     * Take the current leaf object and produce a new one (possibly the same)
     * with the specified key removed.  If the key was previously present in the leaf
     * the method must subtract 1 from the delta so that the size of the array can be
     * properly maintained.
     */
    Holder delete(T leaf,
                     K key,
                     MutableDelta delta);

    /**
     * Look for the specified key in the leaf object and return a Holder
     * that is empty if the key is not in the leaf or else contains the value associated
     * with the key.
     */
    Holder findValue(T leaf,
                        K key);

    /**
     * Look for the specified key in the leaf object and return a Holder
     * that is empty if the key is not in the leaf or else contains a JImmutableMap.Entry
     * associated with the key and value.
     */
    Holder> findEntry(T leaf,
                                                K key);

    /**
     * Return a (possibly empty) Cursor over all of the JImmutableMap.Entries
     * in the specified leaf object.
     */
    Cursor> cursor(T leaf);

    /**
     * Return a (possibly empty) SplitableIterator over all of the JImmutableMap.Entries
     * in the specified leaf object.
     */
    SplitableIterator> iterator(T leaf);
}