FastUserIndex.java

/* 
 * Copyright (C) 2015 Information Retrieval Group at Universidad Autónoma
 * de Madrid, http://ir.ii.uam.es
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package es.uam.eps.ir.ranksys.fast.index;

import es.uam.eps.ir.ranksys.core.index.UserIndex;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import org.jooq.lambda.tuple.Tuple;
import org.jooq.lambda.tuple.Tuple2;
import org.ranksys.core.util.tuples.Tuple2id;
import org.ranksys.core.util.tuples.Tuple2io;
import org.ranksys.core.util.tuples.Tuple2od;
import org.ranksys.core.util.tuples.Tuples;

/**
 * Fast version of UserIndex, where users are internally represented with numerical indices from 0 (inclusive) to the number of indexed users (exclusive).
 *
 * @author Saúl Vargas (saul.vargas@uam.es)
 *
 * @param <U> type of the users
 */
public interface FastUserIndex<U> extends UserIndex<U> {

    @Override
    default boolean containsUser(U u) {
        return user2uidx(u) >= 0;
    }

    @Override
    default Stream<U> getAllUsers() {
        return getAllUidx().mapToObj(this::uidx2user);
    }

    /**
     * Gets all the indices of the users.
     *
     * @return a stream of indexes of users
     */
    default IntStream getAllUidx() {
        return IntStream.range(0, numUsers());
    }

    /**
     * Returns the index assigned to the user.
     *
     * @param u user
     * @return the index of the user, or -1 if the user does not exist
     */
    int user2uidx(U u);

    /**
     * Returns the user represented with the index.
     *
     * @param uidx user index
     * @return the user whose index is uidx
     */
    U uidx2user(int uidx);

    /**
     * Applies FastUserIndex::user2uidx to the first element of the tuple.
     *
     * @param <V> type of value
     * @param tuple user-value tuple
     * @return uidx-value tuple
     */
    default <V> Tuple2io<V> user2uidx(Tuple2<U, V> tuple) {
        return Tuples.tuple(user2uidx(tuple.v1), tuple.v2);
    }

    /**
     * Applies FastUserIndex::uidx2user to the first element of the tuple.
     *
     * @param <V> type of value
     * @param tuple uidx-value tuple
     * @return user-value tuple
     */
    default <V> Tuple2<U, V> uidx2user(Tuple2io<V> tuple) {
        return Tuple.tuple(uidx2user(tuple.v1), tuple.v2);
    }

    /**
     * Applies FastUserIndex::user2uidx to the first element of the tuple.
     *
     * @param tuple user-double tuple
     * @return uidx-double tuple
     */
    default Tuple2id user2uidx(Tuple2od<U> tuple) {
        return Tuples.tuple(user2uidx(tuple.v1), tuple.v2);
    }

    /**
     * Applies FastUserIndex::uidx2user to the first element of the tuple.
     *
     * @param tuple uidx-double tuple
     * @return user-double tuple
     */
    default Tuple2od<U> uidx2user(Tuple2id tuple) {
        return Tuples.tuple(uidx2user(tuple.v1), tuple.v2);
    }

}