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/*
 *  ******************************************************************************
 *  *
 *  *
 *  * This program and the accompanying materials are made available under the
 *  * terms of the Apache License, Version 2.0 which is available at
 *  * https://www.apache.org/licenses/LICENSE-2.0.
 *  *
 *  *  See the NOTICE file distributed with this work for additional
 *  *  information regarding copyright ownership.
 *  * 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.
 *  *
 *  * SPDX-License-Identifier: Apache-2.0
 *  *****************************************************************************
 */

package org.deeplearning4j.iterator.provider;

import lombok.NonNull;
import org.deeplearning4j.iterator.LabeledSentenceProvider;
import org.nd4j.common.base.Preconditions;
import org.nd4j.common.primitives.Pair;
import org.nd4j.common.util.MathUtils;

import java.util.*;

public class CollectionLabeledSentenceProvider implements LabeledSentenceProvider {

    private final List sentences;
    private final List labels;
    private final Random rng;
    private final int[] order;
    private final List allLabels;

    private int cursor = 0;

    public CollectionLabeledSentenceProvider(@NonNull List sentences,
                                             @NonNull List labelsForSentences) {
        this(sentences, labelsForSentences, new Random());
    }

    public CollectionLabeledSentenceProvider(@NonNull List sentences, @NonNull List labelsForSentences,
                                             Random rng) {
        if (sentences.size() != labelsForSentences.size()) {
            throw new IllegalArgumentException("Sentences and labels must be same size (sentences size: "
                    + sentences.size() + ", labels size: " + labelsForSentences.size() + ")");
        }

        this.sentences = sentences;
        this.labels = labelsForSentences;
        this.rng = rng;
        if (rng == null) {
            order = null;
        } else {
            order = new int[sentences.size()];
            for (int i = 0; i < sentences.size(); i++) {
                order[i] = i;
            }

            MathUtils.shuffleArray(order, rng);
        }

        //Collect set of unique labels for all sentences
        Set uniqueLabels = new HashSet<>(labelsForSentences);
        allLabels = new ArrayList<>(uniqueLabels);
        Collections.sort(allLabels);
    }

    @Override
    public boolean hasNext() {
        return cursor < sentences.size();
    }

    @Override
    public Pair nextSentence() {
        Preconditions.checkState(hasNext(), "No next element available");
        int idx;
        if (rng == null) {
            idx = cursor++;
        } else {
            idx = order[cursor++];
        }
        return new Pair<>(sentences.get(idx), labels.get(idx));
    }

    @Override
    public void reset() {
        cursor = 0;
        if (rng != null) {
            MathUtils.shuffleArray(order, rng);
        }
    }

    @Override
    public int totalNumSentences() {
        return sentences.size();
    }

    @Override
    public List allLabels() {
        return allLabels;
    }

    @Override
    public int numLabelClasses() {
        return allLabels.size();
    }
}