/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2002-2016, 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 org.geotools.data.DataUtilities;
import org.geotools.data.FeatureReader;
import org.geotools.data.collection.DelegateFeatureReader;
import org.geotools.data.simple.SimpleFeatureCollection;
import org.geotools.data.simple.SimpleFeatureIterator;
import org.geotools.feature.FeatureCollection;
import org.geotools.feature.collection.DecoratingSimpleFeatureCollection;
import org.geotools.feature.visitor.CountVisitor;
import org.geotools.feature.visitor.FeatureAttributeVisitor;
import org.geotools.filter.FilterAttributeExtractor;
import org.opengis.feature.FeatureVisitor;
import org.opengis.feature.GeometryAttribute;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.feature.type.AttributeDescriptor;
import org.opengis.filter.expression.Expression;
import org.opengis.filter.expression.PropertyName;

/**
 * SimpleFeatureCollection decorator which decorates a feature collection "re-typing" 
 * its schema based on attributes specified in a query.
 * 
 * @author Justin Deoliveira, The Open Planning Project
 * @source $URL$
 */
public class ReTypingFeatureCollection extends DecoratingSimpleFeatureCollection {

	SimpleFeatureType featureType;
    
	public ReTypingFeatureCollection ( FeatureCollection<SimpleFeatureType,SimpleFeature> delegate, SimpleFeatureType featureType ) {
	    this( DataUtilities.simple( delegate), featureType );
	}
	public ReTypingFeatureCollection ( SimpleFeatureCollection delegate, SimpleFeatureType featureType ) {
		super(delegate);
		this.featureType = featureType;
	}
	
	public SimpleFeatureType getSchema() {
	    return featureType;
	}
	
	public  FeatureReader<SimpleFeatureType, SimpleFeature> reader() throws IOException {
		return new DelegateFeatureReader<SimpleFeatureType, SimpleFeature>( getSchema(), features() );
	}
	
	public SimpleFeatureIterator features() {
		return new ReTypingFeatureIterator( delegate.features(), delegate.getSchema(), featureType );
	}

    @Override
    protected boolean canDelegate(FeatureVisitor visitor) {
        return isTypeCompatible(visitor, featureType);
    }
    
    /**
     * Checks if the visitor is accessing only properties available in the specified feature type,
     * or as a special case, if it's a count visitor accessing no properties at all
     *  
     * @param visitor
     * @param featureType
     * @return
     */
    public static boolean isTypeCompatible(FeatureVisitor visitor, SimpleFeatureType featureType) {
        if (visitor instanceof FeatureAttributeVisitor) {
            //pass through if the target schema contains all the necessary attributes
            FilterAttributeExtractor extractor = new FilterAttributeExtractor(featureType);
            for (Expression e : ((FeatureAttributeVisitor) visitor).getExpressions()) {
                e.accept(extractor, null);
            }

            for (PropertyName pname : extractor.getPropertyNameSet()) {
                AttributeDescriptor att = (AttributeDescriptor) pname.evaluate(featureType);
                if (att == null) {
                    return false;
                }
            }
            return true;
        } else if(visitor instanceof CountVisitor) {
            return true;
        }
        return false;
    }
}