// This Source Code is in the Public Domain per: http://litesoft.org/License.txt
package org.litesoft.util;

import java.io.*;

import org.litesoft.commonfoundation.exceptions.*;
import org.litesoft.commonfoundation.interators.*;

/**
 * An Iterator representing the results of repeatedly calling readLine
 * on a BufferedReader.  The underlying data source is any Reader.<p>
 *
 * @author George Smith
 * @version 1.0 7/28/01
 */

public class LineReaderIterator extends Iterators.AbstractReadOnly<String>
{
    /**
     * Construct an Iterator representing the results of repeatedly
     * calling readLine on a BufferedReader.<p>
     *
     * @param pReader the underlying data source (null OK).
     */
    public LineReaderIterator( Reader pReader )
    {
        zReader = Utils.getBufferedReader( pReader );
    }

    private BufferedReader zReader;
    private String zNextLine = null;

    private boolean loadNextLine()
    {
        if ( zReader == null )
        {
            return false;
        }
        try
        {
            if ( null != (zNextLine = zReader.readLine()) )
            {
                return true;
            }
        }
        catch ( IOException e )
        {
            throw new FileSystemException( e );
        }
        closeReader();
        return false;
    }

    private void closeReader()
    {
        try
        {
            zReader.close();
        }
        catch ( IOException ignore )
        {
            // ignoring...
        }
        zReader = null;
    }

    /**
     * If and when the GC runs, and this object is about to be reclaimed, then
     * this method is called, and if the Reader is still open, it is closed.
     */
    @Override
    public void finalize()
            throws Throwable
    {
        if ( zReader != null )
        {
            closeReader();
        }
        super.finalize();
    }

    /**
     * Returns <tt>true</tt>/<tt>false</tt>, if there is another line to be
     * had from next().<p>
     * <p/>
     * Note: The management of the underlying Reader is handled by this method.
     * The first time hasNext() returns false the Reader is closed, and if
     * the Reader is closed, hasNext() returns false.<p>
     *
     * @return <tt>true</tt>/<tt>false</tt>, if there is another line to be
     *         had from next().<p>
     *
     * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html#hasNext()">java.util.Iterator#hasNext()</a>
     * @see #next()
     */
    @Override
    public boolean hasNext()
    {
        return ((zNextLine != null) || loadNextLine());
    }

    /**
     * Returns the next element in the interation.
     *
     * @see <a href="http://java.sun.com/j2se/1.3/docs/api/java/lang/Util/Iterator.html#next()">java.util.Iterator#next()</a>
     */
    @Override
    public String next()
    {
        if ( !hasNext() )
        {
            return super.next(); // throws Exception
        }
        String rv = zNextLine;
        zNextLine = null;
        return rv;
    }

    /**
     * Returns a debug/human friendly String that represents this.<p>
     *
     * @return A String representation of this.
     */
    @Override
    public String toString()
    {
        return "LineReaderIterator: " + (hasNext() ? "has More" : "at End");
    }
}