/**
* 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.Arrays;
import java.util.Iterator;
import java.util.List;
import com.google.common.base.Function;
import com.google.common.collect.Iterators;
import org.apache.mahout.cf.taste.model.Preference;
import org.apache.mahout.cf.taste.model.PreferenceArray;
import org.apache.mahout.common.iterator.CountingIterator;
/**
* <p>
* Like {@link BooleanUserPreferenceArray} but stores preferences for one item (all item IDs the same) rather
* than one user.
* </p>
*
* @see BooleanPreference
* @see BooleanUserPreferenceArray
* @see GenericItemPreferenceArray
*/
public final class BooleanItemPreferenceArray implements PreferenceArray {
private final long[] ids;
private long id;
public BooleanItemPreferenceArray(int size) {
this.ids = new long[size];
this.id = Long.MIN_VALUE; // as a sort of 'unspecified' value
}
public BooleanItemPreferenceArray(List<? extends Preference> prefs, boolean forOneUser) {
this(prefs.size());
int size = prefs.size();
for (int i = 0; i < size; i++) {
Preference pref = prefs.get(i);
ids[i] = forOneUser ? pref.getItemID() : pref.getUserID();
}
if (size > 0) {
id = forOneUser ? prefs.get(0).getUserID() : prefs.get(0).getItemID();
}
}
/**
* This is a private copy constructor for clone().
*/
private BooleanItemPreferenceArray(long[] ids, long id) {
this.ids = ids;
this.id = id;
}
@Override
public int length() {
return ids.length;
}
@Override
public Preference get(int i) {
return new PreferenceView(i);
}
@Override
public void set(int i, Preference pref) {
id = pref.getItemID();
ids[i] = pref.getUserID();
}
@Override
public long getUserID(int i) {
return ids[i];
}
@Override
public void setUserID(int i, long userID) {
ids[i] = userID;
}
@Override
public long getItemID(int i) {
return id;
}
/**
* {@inheritDoc}
*
* Note that this method will actually set the item ID for <em>all</em> preferences.
*/
@Override
public void setItemID(int i, long itemID) {
id = itemID;
}
/**
* @return all user IDs
*/
@Override
public long[] getIDs() {
return ids;
}
@Override
public float getValue(int i) {
return 1.0f;
}
@Override
public void setValue(int i, float value) {
throw new UnsupportedOperationException();
}
@Override
public void sortByUser() {
Arrays.sort(ids);
}
@Override
public void sortByItem() { }
@Override
public void sortByValue() { }
@Override
public void sortByValueReversed() { }
@Override
public boolean hasPrefWithUserID(long userID) {
for (long id : ids) {
if (userID == id) {
return true;
}
}
return false;
}
@Override
public boolean hasPrefWithItemID(long itemID) {
return id == itemID;
}
@Override
public BooleanItemPreferenceArray clone() {
return new BooleanItemPreferenceArray(ids.clone(), id);
}
@Override
public int hashCode() {
return (int) (id >> 32) ^ (int) id ^ Arrays.hashCode(ids);
}
@Override
public boolean equals(Object other) {
if (!(other instanceof BooleanItemPreferenceArray)) {
return false;
}
BooleanItemPreferenceArray otherArray = (BooleanItemPreferenceArray) other;
return id == otherArray.id && Arrays.equals(ids, otherArray.ids);
}
@Override
public Iterator<Preference> iterator() {
return Iterators.transform(new CountingIterator(length()),
new Function<Integer, Preference>() {
@Override
public Preference apply(Integer from) {
return new PreferenceView(from);
}
});
}
@Override
public String toString() {
StringBuilder result = new StringBuilder(10 * ids.length);
result.append("BooleanItemPreferenceArray[itemID:");
result.append(id);
result.append(",{");
for (int i = 0; i < ids.length; i++) {
if (i > 0) {
result.append(',');
}
result.append(ids[i]);
}
result.append("}]");
return result.toString();
}
private final class PreferenceView implements Preference {
private final int i;
private PreferenceView(int i) {
this.i = i;
}
@Override
public long getUserID() {
return BooleanItemPreferenceArray.this.getUserID(i);
}
@Override
public long getItemID() {
return BooleanItemPreferenceArray.this.getItemID(i);
}
@Override
public float getValue() {
return 1.0f;
}
@Override
public void setValue(float value) {
throw new UnsupportedOperationException();
}
}
}