/*
    * Copyright 2012 Olivier Godineau
    * 
    * Licensed under the Apache License, Version 2.0 (the "License"); you may not
    * use this file except in compliance with the License. You may obtain a copy of
    * the License at http://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.
   */
  package olg.csv.base;
  
  import java.io.IOException;
  import java.util.NoSuchElementException;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A "Proxy" reader which Provides a mecanism to skip empty row.
   * 
   * @author Olivier Godineau
   * 
   */
  public class IgnoreNullReader implements IReader {
  	/**
  	 * The class logger.
  	 */
  	private static final Logger LOGGER = LoggerFactory.getLogger(IgnoreNullReader.class);
  	/**
  	 * the original reader.
  	 */
  	private final IReader reader;
  
  	/**
  	 * the last row retrieved from the original reader.
  	 */
  	private Row currentRow = null;
  	/**
  	 * 
  	 */
  	private boolean next;
  	/**
  	 * because next() method even if returns the next element, loads the
  	 * following row. During loading the following row a readException could
  	 * occur. So we need to keep this exception to throw it on the following
  	 * call of next() method.
  	 */
  	private ReaderException exception = null;
  
  	/**
  	 * 
  	 * @param reader
  	 *            a concret reader
  	 */
  	public IgnoreNullReader(IReader reader) {
  		super();
  		if (reader == null) {
  			throw new IllegalArgumentException(IgnoreNullReader.class.getSimpleName()
  					+ " Constructor IReader argument must not be null");
  		}
  		this.reader = reader;
  		this.currentRow = setNext();
  	}
  	/**
  	 * @return true if exists a next not empty row.
  	 */
  	public boolean hasNext() {
  		return next;
  	}
  
  	/**
  	 * 
  	 * @return the next not empty row.
  	 */
  	public Row next() {
  		if (!hasNext()) {
  			throw new NoSuchElementException();
  		}
  		Row retour = currentRow;
  		ReaderException err = this.exception;
  		try {
  			currentRow = setNext();
  		} catch (ReaderException e) {
  			this.exception = e;
  		}
  		if (err != null) {
  
  			throw err;
  		}
  
  		return retour;
  	}
  
  	/**
  	 * 
 	 * @return the next not empty row.
 	 */
 	private Row setNext() {
 		Row retour = null;
 
 		do {
 			if (reader.hasNext()) {
 				retour = reader.next();
 				next = true;
 			} else {
 				next = false;
 				retour = null;
 			}
 		} while (retour != null && retour.isEmpty());
 		return retour;
 	}
 
 	/**
 	 * Throws UnsupportedOperationException.
 	 */
 	public void remove() {
 		throw new UnsupportedOperationException();
 
 	}
 
 	/**
 	 * close the original reader.
 	 */
 	public void close() {
 		try {
 			reader.close();
 		} catch (IOException e) {
 			LOGGER.info("Error on closing reader", e);
 		}
 	}
 
 	/**
 	 * @return the original withHeaders attribute.
 	 */
 	public boolean isWithHeaders() {
 		return reader.isWithHeaders();
 	}
 
 }