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package org.broadinstitute.hellbender.utils.nio;

import htsjdk.samtools.util.IOUtil;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.broadinstitute.hellbender.exceptions.UserException;
import org.broadinstitute.hellbender.utils.Utils;

import java.io.IOException;
import java.nio.charset.CharacterCodingException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Iterator;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.stream.Stream;
import org.broadinstitute.hellbender.utils.io.IOUtils;

/**
 * Iterate through the lines of a Path. Works for anything you can point
 * a Path to, such as a normal file or anything you have an NIO provider
 * for (e.g. GCS).
 */
public class PathLineIterator implements AutoCloseable, Iterable {
    private final Stream lines;

    /**
     * Returns an iterator so you can iterate over the lines in the text file like so:
     * for (String line: new PathLineIterator(path)) {
     *   // do something with the line
     * }
     *
     * It's also closeable so you can close it when done, or use it in a try-with-resources
     * to close it automatically.
     *
     * If the file name ends in ".gz", this will decompress it automatically.
     *
     * Consider also using XReadLines if you need trimming or skipping comments.
     *
     * @param path path to a text file.
     */
    public PathLineIterator(final Path path) {
        try {
            InputStream is = Files.newInputStream(Utils.nonNull(path, "path shouldn't be null"));
            if (IOUtil.hasBlockCompressedExtension(path)) {
                is = IOUtils.makeZippedInputStream(is);
            }
            BufferedReader br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
            lines = br.lines();
        }
        catch (final CharacterCodingException ex ) {
            throw new UserException("Error detected in file character encoding.  Possible inconsistent character encodings within the file: " + path.toUri().toString(), ex);
        }
        catch (final IOException x) {
            throw new UserException("Error reading " + path.toUri().toString(), x);
        }
    }

    @Override
    public void close() {
        lines.close();
    }

    @Override
    public Iterator iterator() {
        return lines.iterator();
    }

    @Override
    public void forEach(Consumer action) {
        lines.forEach(action);
    }

    @Override
    public Spliterator spliterator() {
        return lines.spliterator();
    }

}