package eu.dnetlib.data.hadoop.hdfs;

import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Writable;

import eu.dnetlib.miscutils.collections.Pair;

/**
 * <p>
 * {@link Iterable} counterpart to {@link SequenceFileIterator}.
 * </p>
 */
public final class SequenceFileIterable<K extends Writable, V extends Writable> implements Iterable<Pair<K, V>> {

	private final Path path;
	private final boolean reuseKeyValueInstances;
	private final Configuration conf;

	/**
	 * Like {@link #SequenceFileIterable(Path, boolean, Configuration)} but key and value instances are not reused by
	 * default.
	 *
	 * @param path
	 *            file to iterate over
	 */
	public SequenceFileIterable(Path path, Configuration conf) {
		this(path, false, conf);
	}

	/**
	 * @param path
	 *            file to iterate over
	 * @param reuseKeyValueInstances
	 *            if true, reuses instances of the key and value object instead of creating a new one for each read from
	 *            the file
	 */
	public SequenceFileIterable(Path path, boolean reuseKeyValueInstances, Configuration conf) {
		this.path = path;
		this.reuseKeyValueInstances = reuseKeyValueInstances;
		this.conf = conf;
	}

	@Override
	public Iterator<Pair<K, V>> iterator() {
		try {
			return new SequenceFileIterator<K, V>(path, reuseKeyValueInstances, conf);
		} catch (IOException ioe) {
			throw new IllegalStateException(path.toString(), ioe);
		}
	}

}