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/*******************************************************************************
 * Copyright (c) 2015-2018 Skymind, Inc.
 *
 * 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.
 *
 * 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.nd4j.linalg.dataset.api.iterator;

import org.nd4j.linalg.dataset.DataSet;
import org.nd4j.linalg.dataset.api.DataSetPreProcessor;
import org.nd4j.linalg.dataset.api.iterator.fetcher.DataSetFetcher;

import java.util.List;
import java.util.NoSuchElementException;

/**
 * Baseline implementation includes
 * control over the data fetcher and some basic
 * getters for metadata
 *
 * @author Adam Gibson
 */
public class BaseDatasetIterator implements DataSetIterator {


    private static final long serialVersionUID = -116636792426198949L;
    protected int batch, numExamples;
    protected DataSetFetcher fetcher;
    protected DataSetPreProcessor preProcessor;


    public BaseDatasetIterator(int batch, int numExamples, DataSetFetcher fetcher) {
        this.batch = batch;
        if (numExamples < 0)
            numExamples = fetcher.totalExamples();

        this.numExamples = numExamples;
        this.fetcher = fetcher;
    }

    @Override
    public boolean hasNext() {
        return fetcher.hasMore() && fetcher.cursor() < numExamples;
    }

    @Override
    public DataSet next() {
        if(!hasNext())
            throw new NoSuchElementException("No next element - hasNext() == false");
        int next = Math.min(batch, numExamples - fetcher.cursor());
        fetcher.fetch(next);
        DataSet ds = fetcher.next();
        if (preProcessor != null)
            preProcessor.preProcess(ds);
        return ds;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException();
    }

    @Override
    public int inputColumns() {
        return fetcher.inputColumns();
    }

    @Override
    public int totalOutcomes() {
        return fetcher.totalOutcomes();
    }

    @Override
    public boolean resetSupported() {
        return true;
    }

    @Override
    public boolean asyncSupported() {
        return true;
    }

    @Override
    public void reset() {
        fetcher.reset();
    }

    @Override
    public int batch() {
        return batch;
    }

    /**
     * Set a pre processor
     *
     * @param preProcessor a pre processor to set
     */
    @Override
    public void setPreProcessor(DataSetPreProcessor preProcessor) {
        this.preProcessor = preProcessor;
    }

    @Override
    public DataSetPreProcessor getPreProcessor() {
        return preProcessor;
    }

    @Override
    public List getLabels() {
        return null;
    }

    @Override
    public DataSet next(int num) {
        fetcher.fetch(num);
        DataSet next = fetcher.next();
        if (preProcessor != null)
            preProcessor.preProcess(next);
        return next;
    }


}