/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 * 
 *    (C) 2002-2008, 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.util;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;

import org.geotools.factory.Hints;

/**
 * Converts among arrays and different collection classes.
 * <p>
 * THe following conversions are supported:
 * <ul>
 *   <li>Collection to Collection where collections are different types ( ex list to set )
 *   <li>Collection to Array
 *   <li>Array to Collection
 *   <li>Array to Array where the declared type of the target array is assignable from 
 *   the declared type of the source array
 * </ul>
 * </p>
 * 
 * @author Justin Deoliveira, The Open Planning Project
 *
 *
 *
 * @source $URL$
 */
public class CollectionConverterFactory implements ConverterFactory {

    /**
     * Converter for collection to collection
     */
    protected static final Converter CollectionToCollection = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
            //if source is already an instance nevermind
            if ( target.isInstance( source ) ) {
                return source;
            }
            
            //dynamically create and add
            Collection converted = newCollection( target );
            if ( converted != null ) {
                converted.addAll( (Collection) source );    
            }
          
            return converted;
        }
        
    };
    
    /**
     * Converter for collection to array.
     */
    protected static final Converter CollectionToArray = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
            Collection s = (Collection) source;
            Object array = Array.newInstance(target.getComponentType(), s.size());
            
            try {
                int x = 0;
                for ( Iterator i = s.iterator(); i.hasNext(); x++ ) {
                    Array.set( array, x, i.next() );
                }
                
                return array;
            }
            catch( Exception e ) {
                //Means an incompatable type assignment
                
            }
             
            return null;
        }
        
    };
    
    /**
     * Converter for array to collection.
     */
    protected static final Converter ArrayToCollection = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
            Collection collection = newCollection(target);
            if ( collection != null ) {
                int length = Array.getLength(source);
                for ( int i = 0; i < length; i++ ) {
                    collection.add( Array.get( source, i) );
                }
            }
            
            return collection;
        }
        
    };
    
    /**
     * Converter for array to array.
     */
    protected static final Converter ArrayToArray = new Converter() {

        public Object convert(Object source, Class target) throws Exception {
          //get the individual component types
            Class s = source.getClass().getComponentType();
            Class t = target.getComponentType();

            //make sure the source can be assiigned to the target
            if ( t.isAssignableFrom(s) ) {
                int length = Array.getLength(source);
                Object converted = Array.newInstance( t, length );
               
                for ( int i = 0; i < length; i++ ) {
                    Array.set(converted, i, Array.get( source, i ) );
                }
                
                return converted;
            }
            
            return null;
        }
    };
    
    protected static Collection newCollection( Class target ) throws Exception {
        if ( target.isInterface() ) {
            //try the common ones
            if ( List.class.isAssignableFrom( target ) ) {
                return new ArrayList();
            }
            if ( SortedSet.class.isAssignableFrom( target ) ) {
                return new TreeSet();
            }
            else if ( Set.class.isAssignableFrom( target ) ) {
                return new HashSet();
            }
            
            //could not figure out
            return null;
        }
        else {
            //instantiate directly
            return (Collection) target.newInstance();
        }
    }
    public Converter createConverter(Class source, Class target, Hints hints) {
        if ( ( Collection.class.isAssignableFrom( source ) || source.isArray() ) 
            && ( Collection.class.isAssignableFrom( target ) || target.isArray() ) ) {
            
            //both collections?
            if ( Collection.class.isAssignableFrom( source ) && 
                    Collection.class.isAssignableFrom( target ) ) {
               return CollectionToCollection;
            }
            
            //both arrays?
            if ( source.getClass().isArray() && target.isArray() ) {
                return ArrayToArray;
            }
            
            //collection to array?
            if ( Collection.class.isAssignableFrom( source ) && target.isArray() ) {
               return CollectionToArray;
            }
            
            //array to collection?
            if ( source.isArray() && Collection.class.isAssignableFrom( target ) ) {
                return ArrayToCollection;
            }
        }
            
        return null;
    }
}