org.conqat.lib.commons.datamining.RecommenderRatingDatabase Maven / Gradle / Ivy

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Provides common utility functions

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/*
 * Copyright (c) CQSE GmbH
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.conqat.lib.commons.datamining;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

import org.conqat.lib.commons.collections.CollectionUtils;
import org.conqat.lib.commons.collections.ListMap;
import org.conqat.lib.commons.collections.UnmodifiableSet;

/**
 * Binary rating database. A rating is either 'like' or 'unrated'.
 */
public class RecommenderRatingDatabase implements Serializable {

	/** Serial ID */
	private static final long serialVersionUID = 1L;

	/** The data */
	private final ListMap data = new ListMap<>();

	/** Returns all users contained in this database. */
	public UnmodifiableSet getUsers() {
		return CollectionUtils.asUnmodifiable(data.getKeys());
	}

	/** Adds the given users to this rating database. */
	public void add(IRecommenderUser user, Set likedItems) {
		data.addAll(user, likedItems);
	}

	/** Removes the user completely */
	public void remove(IRecommenderUser user) {
		data.removeCollection(user);
	}

	/**
	 * Returns the items liked by the given user. If no entry for this user is found an
	 * IllegalArgumentException is thrown.
	 */
	public Set getLikedItems(IRecommenderUser user) {
		if (!data.containsCollection(user)) {
			throw new IllegalArgumentException("No such user: " + user);
		}
		return new HashSet<>(data.getCollection(user));
	}

	/**
	 * Constructs a new {@link RecommenderRatingDatabase} from the given shopping baskets
	 */
	public static  RecommenderRatingDatabase fromShoppingBaskets(Set> shoppingBaskets) {
		RecommenderRatingDatabase ratingDatabase = new RecommenderRatingDatabase<>();
		for (Set basket : shoppingBaskets) {
			ratingDatabase.add(new ShoppingBasketUser(basket), basket);
		}
		return ratingDatabase;
	}

	/** {@inheritDoc} */
	@Override
	public String toString() {
		return data.toString();
	}
}