/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.mahout.cf.taste.impl.model;
import java.util.Collection;
import org.apache.mahout.cf.taste.common.NoSuchItemException;
import org.apache.mahout.cf.taste.common.NoSuchUserException;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
import org.apache.mahout.cf.taste.impl.common.LongPrimitiveIterator;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.model.PreferenceArray;
import com.google.common.base.Preconditions;
/**
* <p>
* This {@link DataModel} decorator class is useful in a situation where you wish to recommend to a user that
* doesn't really exist yet in your actual {@link DataModel}. For example maybe you wish to recommend DVDs to
* a user who has browsed a few titles on your DVD store site, but, the user is not yet registered.
* </p>
*
* <p>
* This enables you to temporarily add a temporary user to an existing {@link DataModel} in a way that
* recommenders can then produce recommendations anyway. To do so, wrap your real implementation in this
* class:
* </p>
*
* <p>
*
* <pre>
* DataModel realModel = ...;
* DataModel plusModel = new PlusAnonymousUserDataModel(realModel);
* ...
* ItemSimilarity similarity = new LogLikelihoodSimilarity(realModel); // not plusModel
* </pre>
*
* </p>
*
* <p>
* But, you may continue to use {@code realModel} as input to other components. To recommend, first construct and
* set the temporary user information on the model and then simply call the recommender. The
* {@code synchronized} block exists to remind you that this is of course not thread-safe. Only one set
* of temp data can be inserted into the model and used at one time.
* </p>
*
* <p>
*
* <pre>
* Recommender recommender = ...;
* ...
* synchronized(...) {
* PreferenceArray tempPrefs = ...;
* plusModel.setTempPrefs(tempPrefs);
* recommender.recommend(PlusAnonymousUserDataModel.TEMP_USER_ID, 10);
* plusModel.setTempPrefs(null);
* }
* </pre>
*
* </p>
*/
public final class PlusAnonymousUserDataModel implements DataModel {
public static final long TEMP_USER_ID = Long.MIN_VALUE;
private final DataModel delegate;
private PreferenceArray tempPrefs;
private final FastIDSet prefItemIDs;
public PlusAnonymousUserDataModel(DataModel delegate) {
this.delegate = delegate;
this.prefItemIDs = new FastIDSet();
}
public void setTempPrefs(PreferenceArray prefs) {
Preconditions.checkArgument(prefs != null && prefs.length() > 0, "prefs is null or empty");
this.tempPrefs = prefs;
this.prefItemIDs.clear();
for (int i = 0; i < prefs.length(); i++) {
this.prefItemIDs.add(prefs.getItemID(i));
}
}
public void clearTempPrefs() {
tempPrefs = null;
prefItemIDs.clear();
}
@Override
public LongPrimitiveIterator getUserIDs() throws TasteException {
if (tempPrefs == null) {
return delegate.getUserIDs();
}
return new PlusAnonymousUserLongPrimitiveIterator(delegate.getUserIDs(), TEMP_USER_ID);
}
@Override
public PreferenceArray getPreferencesFromUser(long userID) throws TasteException {
if (userID == TEMP_USER_ID) {
if (tempPrefs == null) {
throw new NoSuchUserException(TEMP_USER_ID);
}
return tempPrefs;
}
return delegate.getPreferencesFromUser(userID);
}
@Override
public FastIDSet getItemIDsFromUser(long userID) throws TasteException {
if (userID == TEMP_USER_ID) {
if (tempPrefs == null) {
throw new NoSuchUserException(TEMP_USER_ID);
}
return prefItemIDs;
}
return delegate.getItemIDsFromUser(userID);
}
@Override
public LongPrimitiveIterator getItemIDs() throws TasteException {
return delegate.getItemIDs();
// Yeah ignoring items that only the plus-one user knows about... can't really happen
}
@Override
public PreferenceArray getPreferencesForItem(long itemID) throws TasteException {
if (tempPrefs == null) {
return delegate.getPreferencesForItem(itemID);
}
PreferenceArray delegatePrefs = null;
try {
delegatePrefs = delegate.getPreferencesForItem(itemID);
} catch (NoSuchItemException nsie) {
// OK. Probably an item that only the anonymous user has
}
for (int i = 0; i < tempPrefs.length(); i++) {
if (tempPrefs.getItemID(i) == itemID) {
int length = delegatePrefs == null ? 0 : delegatePrefs.length();
PreferenceArray newPreferenceArray = new GenericItemPreferenceArray(length + 1);
for (int j = 0; j < length; j++) {
newPreferenceArray.setUserID(j, delegatePrefs.getUserID(j));
newPreferenceArray.setItemID(j, delegatePrefs.getItemID(j));
newPreferenceArray.setValue(j, delegatePrefs.getValue(j));
}
newPreferenceArray.setUserID(length, tempPrefs.getUserID(i));
newPreferenceArray.setItemID(length, tempPrefs.getItemID(i));
newPreferenceArray.setValue(length, tempPrefs.getValue(i));
newPreferenceArray.sortByUser();
return newPreferenceArray;
}
}
if (delegatePrefs == null) {
// No, didn't find it among the anonymous user prefs
throw new NoSuchItemException(itemID);
}
return delegatePrefs;
}
@Override
public Float getPreferenceValue(long userID, long itemID) throws TasteException {
if (userID == TEMP_USER_ID) {
if (tempPrefs == null) {
throw new NoSuchUserException(TEMP_USER_ID);
}
for (int i = 0; i < tempPrefs.length(); i++) {
if (tempPrefs.getItemID(i) == itemID) {
return tempPrefs.getValue(i);
}
}
return null;
}
return delegate.getPreferenceValue(userID, itemID);
}
@Override
public Long getPreferenceTime(long userID, long itemID) throws TasteException {
if (userID == TEMP_USER_ID) {
if (tempPrefs == null) {
throw new NoSuchUserException(TEMP_USER_ID);
}
return null;
}
return delegate.getPreferenceTime(userID, itemID);
}
@Override
public int getNumItems() throws TasteException {
return delegate.getNumItems();
}
@Override
public int getNumUsers() throws TasteException {
return delegate.getNumUsers() + (tempPrefs == null ? 0 : 1);
}
@Override
public int getNumUsersWithPreferenceFor(long itemID) throws TasteException {
if (tempPrefs == null) {
return delegate.getNumUsersWithPreferenceFor(itemID);
}
boolean found = false;
for (int i = 0; i < tempPrefs.length(); i++) {
if (tempPrefs.getItemID(i) == itemID) {
found = true;
break;
}
}
return delegate.getNumUsersWithPreferenceFor(itemID) + (found ? 1 : 0);
}
@Override
public int getNumUsersWithPreferenceFor(long itemID1, long itemID2) throws TasteException {
if (tempPrefs == null) {
return delegate.getNumUsersWithPreferenceFor(itemID1, itemID2);
}
boolean found1 = false;
boolean found2 = false;
for (int i = 0; i < tempPrefs.length() && !(found1 && found2); i++) {
long itemID = tempPrefs.getItemID(i);
if (itemID == itemID1) {
found1 = true;
}
if (itemID == itemID2) {
found2 = true;
}
}
return delegate.getNumUsersWithPreferenceFor(itemID1, itemID2) + (found1 && found2 ? 1 : 0);
}
@Override
public void setPreference(long userID, long itemID, float value) throws TasteException {
if (userID == TEMP_USER_ID) {
if (tempPrefs == null) {
throw new NoSuchUserException(TEMP_USER_ID);
}
throw new UnsupportedOperationException();
}
delegate.setPreference(userID, itemID, value);
}
@Override
public void removePreference(long userID, long itemID) throws TasteException {
if (userID == TEMP_USER_ID) {
if (tempPrefs == null) {
throw new NoSuchUserException(TEMP_USER_ID);
}
throw new UnsupportedOperationException();
}
delegate.removePreference(userID, itemID);
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
delegate.refresh(alreadyRefreshed);
}
@Override
public boolean hasPreferenceValues() {
return delegate.hasPreferenceValues();
}
@Override
public float getMaxPreference() {
return delegate.getMaxPreference();
}
@Override
public float getMinPreference() {
return delegate.getMinPreference();
}
}