/*
 * Copyright (c) 2006 Israfil Consulting Services Corporation
 * Copyright (c) 2006 Christian Edward Gruber
 * All Rights Reserved
 * 
 * This software is licensed under the Berkeley Standard Distribution license,
 * (BSD license), as defined below:
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this 
 *    list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice, 
 *    this list of conditions and the following disclaimer in the documentation 
 *    and/or other materials provided with the distribution.
 * 3. Neither the name of Israfil Consulting Services nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software without 
 *    specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
 * IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY 
 * OF SUCH DAMAGE.
 * 
 * $Id: IterableResultSet.java 26 2006-02-13 16:35:44Z cgruber $
 */
package net.israfil.foundation.collections;

import java.lang.ref.WeakReference;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * A simple wrapper that provides an Iterable implementation back-ended 
 * by a result-set.  Allows a ResultSet to be used in a JDK 5.0 extended
 * for-loop syntax.
 * 
 * No result set can have more than one Iterable wrapper around it at a time.
 * However, it is impossible for this object to know implicitly when it is 
 * no longer required (to free the reference).  Therefore, when this 
 * wrapper is concluded, it should be disposed of via the dispose() method.
 * 
 * @author <a href="mailto:cgruber@israfil.net">Christian Edward Gruber </a>
 */
public class IterableResultSet implements Iterable<Map<String,Object>> {

	protected static final Map<ResultSet,IterableResultSet> iterables = new WeakHashMap<ResultSet,IterableResultSet>();
	protected final WeakReference<ResultSet> resultRef;
	
	public IterableResultSet(ResultSet result) {
		if (iterables.containsKey(result)) throw new RuntimeException("Cannot have two IterableResultSet wrappers around the same resultset.");
		this.resultRef = new WeakReference<ResultSet>(result);
	}
	
	public Iterator<Map<String,Object>> iterator() {
		if (resultRef.get() == null) throw new RuntimeException("ResultSet object not available to iterate.");
		return new ResultSetIterator(resultRef.get());
	}
	
	public void dispose() {
		ResultSet rs = resultRef.get();
		if (rs == null) return;
		if (iterables.containsKey(rs)) {
			iterables.get(rs).dispose();
		}
		resultRef.clear();
	}

	public static class ResultSetIterator implements Iterator<Map<String,Object>> {
		private static final Logger logger = Logger.getLogger(ResultSetIterator.class.getName());
		protected ResultSet result;
		
		boolean hasNext = true;
		

		public ResultSetIterator(ResultSet result) {
			this.result = result;
			try {	
				hasNext = result.first();
			} catch (SQLException e) {
				throw new RuntimeException(e);
			}
		}
		
		public boolean hasNext() {
			return hasNext;
		}

		public Map<String,Object> next() {
			try {
				Map<String,Object> row = new HashMap<String,Object>();
				for(int i = 1; i <= result.getMetaData().getColumnCount(); i++) {
					row.put(result.getMetaData().getColumnName(i),result.getObject(i));
				}
				hasNext = result.next();
				return row;
			} catch (SQLException e) {
				logger.log(Level.FINER,"SQLException thrown while iterating across result set.",e);
				return null;				
			}
		}

		public void remove() {
			throw new UnsupportedOperationException("Removal of records from underlying result set not supported.");
		}
		
		public void dispose() {
			if (iterables.containsKey(result)) iterables.remove(result);
			result = null;
		}
		
		public void finalize() throws Throwable {
			dispose();
			super.finalize();
		}
	}
}