/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2004-2008, Open Source Geospatial Foundation (OSGeo)
 *    
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License as published by the Free Software Foundation;
 *    version 2.1 of the License.
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 */
package org.geotools.data.store;

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

import org.geotools.data.FeatureWriter;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;

/**
 * An iterator wrapper for a FeatureWriter - for use with
 * an AbstractFeatureCollection.
 * <p>
 * There is no reason modify this class, subclasses that wish
 * to work with a custom iterator need just that - a custom iterator.
 * <p>
 * <p>
 * The use of this class against a SimpleFeatureSource not backed by
 * a Transaction may *really* cut into performance. Consider if
 * you will the overhead involved in writing out each feature into
 * a temporary file (when the user may not even modify anything).
 * </p>
 * @author jgarnett
 * @since 2.1.RC0
 * @source $URL$
 */
final class FeatureWriterIterator implements Iterator<SimpleFeature> {
    FeatureWriter<SimpleFeatureType, SimpleFeature> writer;    
    public FeatureWriterIterator( FeatureWriter<SimpleFeatureType, SimpleFeature> writer ){
        this.writer = writer;
    }
    public boolean hasNext() {
        try {
            if( writer == null ) {
                return false;
            }
            writer.write(); // write out any "changes" made
            if( writer.hasNext() ){
                return true;
            }
            else {
                close();
                return false;
                // auto close because we don't trust client
                // code to call close 
            }
        } catch (IOException e) {
            close();
            return false; // failure sounds like lack of next to me
        }        
    }

    public SimpleFeature next() {
        if( writer == null ) {
            throw new NoSuchElementException( "Iterator has been closed" );            
        }
        try {
            return writer.next();
        } catch (IOException io) {
            NoSuchElementException problem = new NoSuchElementException( "Could not obtain the next feature:"+io );
            problem.initCause( io );
            throw problem;
        }       
    }
    public void remove() {
        try {
            writer.remove();
        } catch (IOException problem) {
            throw (IllegalStateException) new IllegalStateException( "Could not remove feature" ).initCause( problem ); 
        }        
    }
    /**
     * This method only needs package visability as only AbstractFeatureCollection
     * is trusted enough to call it.
     */
    void close(){
        if( writer != null){
            try {
                writer.close();
            } catch (IOException e) {
                // sorry but iterators die quitely in the night
            }
            writer = null;
        }
    }
};