/*
 * Copyright 2002-2004 the original author or authors.
 * 
 * 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 org.springframework.jdbc.support;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import org.springframework.dao.DataRetrievalFailureException;
import org.springframework.dao.InvalidDataAccessApiUsageException;

/** 
 * An implementation of the KeyHolder interface, to be used for holding
 * auto-generated keys as potentially returned by JDBC insert statements.
 *
 * <p>Create an instance of this class for each insert operation, and pass
 * it to the corresponding JdbcTemplate respectively SqlUpdate methods.
 *
 * @author Thomas Risberg
 * @see org.springframework.jdbc.core.JdbcTemplate
 * @see org.springframework.jdbc.object.SqlUpdate
 */
public class GeneratedKeyHolder implements KeyHolder {

	private final List keyList;

	/**
	 * Create a new GeneratedKeyHolder with a default list.
	 */
	public GeneratedKeyHolder() {
		this.keyList = new LinkedList();
	}

	/**
	 * Create a new GeneratedKeyHolder with a given list.
	 * @param keyList a list to hold maps of keys
	 */
	public GeneratedKeyHolder(List keyList) {
		this.keyList = keyList;
	}

	public Number getKey() throws InvalidDataAccessApiUsageException, DataRetrievalFailureException {
		if (this.keyList.size() == 0) {
			return null;
		}
		if (this.keyList.size() > 1 || ((Map) this.keyList.get(0)).size() > 1) {
			throw new InvalidDataAccessApiUsageException(
					"The getKey method should only be used when a single key is returned.  " +
					"The current key entry contains multiple keys: " + this.keyList);
		}
		Iterator keyIter = ((Map) this.keyList.get(0)).values().iterator();
		if (keyIter.hasNext()) {
			Object key = keyIter.next();
			if (!(key instanceof Number)) {
				throw new DataRetrievalFailureException(
						"The generated key is not of a supported numeric type. " +
						"Unable to cast [" + key.getClass().getName() + "] to [" + Number.class.getName() + "]");
			}
			return (Number) key;
		}
		else {
			throw new DataRetrievalFailureException("Unable to retrieve the generated key. " +
																							"Check that the table has an identity column enabled.");
		}
	}

	public Map getKeys() throws InvalidDataAccessApiUsageException {
		if (this.keyList.size() == 0) {
			return null;
		}
		if (this.keyList.size() > 1)
			throw new InvalidDataAccessApiUsageException(
					"The getKeys method should only be used when keys for a single row are returned.  " +
					"The current key list contains keys for multiple rows: " + this.keyList);
		return (Map) this.keyList.get(0);
	}

	public List getKeyList() {
		return keyList;
	}

}
