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/*
 * 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 hivemall.ftvec.ranking;

import hivemall.utils.collections.lists.IntArrayList;
import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
import it.unimi.dsi.fastutil.ints.IntIterator;

import java.util.BitSet;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

public class PositiveOnlyFeedback {

    @Nonnull
    protected final Int2ObjectMap rows;

    protected int maxItemId;
    protected int totalFeedbacks;

    public PositiveOnlyFeedback(int maxItemId) {
        this.rows = new Int2ObjectOpenHashMap(1024);
        this.maxItemId = maxItemId;
        this.totalFeedbacks = 0;
    }

    public int getNumUsers() {
        return rows.size();
    }

    public void setMaxItemId(int maxItemId) {
        this.maxItemId = maxItemId;
    }

    public int getMaxItemId() {
        return maxItemId;
    }

    public int getTotalFeedbacks() {
        return totalFeedbacks;
    }

    @Nonnull
    public int[] getUsers() {
        final int size = rows.size();
        final int[] keys = new int[size];
        final IntIterator itor = rows.keySet().iterator();
        for (int i = 0; i < size; i++) {
            if (!itor.hasNext()) {
                throw new IllegalStateException();
            }
            int key = itor.nextInt();
            keys[i] = key;
        }
        return keys;
    }

    public void getUsers(@Nonnull final BitSet bitset) {
        for (int key : rows.keySet()) {
            bitset.set(key);
        }
    }

    @Nullable
    public IntArrayList getItems(final int userId, boolean nonEmptyCheck) {
        IntArrayList items = rows.get(userId);
        if (nonEmptyCheck) {
            if (items == null || items.isEmpty()) {
                throw new IllegalStateException("Found empty items for user: " + userId);
            }
        }
        return items;
    }

    public void removeFeedback(final int userId) {
        IntArrayList items = rows.remove(userId);
        if (items != null && !items.isEmpty()) {
            this.totalFeedbacks -= items.size();
        }
    }

    public void addFeedback(final int userId, @Nonnull final IntArrayList itemIds) {
        validateIndex(userId);
        if (itemIds.isEmpty()) {
            return;
        }

        IntArrayList old = rows.put(userId, itemIds);
        if (old != null) {
            throw new IllegalStateException("Entry already exists in row: " + userId);
        }

        this.totalFeedbacks += itemIds.size();
    }

    protected static void validateIndex(final int index) {
        if (index < 0) {
            throw new IllegalArgumentException("Negative index is not allowed: " + index);
        }
    }

    protected static void validateIndex(final int user, final int item) {
        if (user < 0) {
            throw new IllegalArgumentException("Negative user index is not allowed: " + user);
        }
        if (item < 0) {
            throw new IllegalArgumentException("Negative item index is not allowed: " + item);
        }
    }


}