/*
    * Copyright 2002-2012 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;
  
  /**
   * Default implementation of the {@link 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 {@link org.springframework.jdbc.core.JdbcTemplate}
   * or {org.springframework.jdbc.object.SqlUpdate} methods.
   *
   * @author Thomas Risberg
   * @author Juergen Hoeller
   * @since 1.1
   */
  public class GeneratedKeyHolder implements KeyHolder {
  
  	private final List<Map<String, Object>> keyList;
  
  
  	/**
  	 * Create a new GeneratedKeyHolder with a default list.
  	 */
  	public GeneratedKeyHolder() {
  		this.keyList = new LinkedList<Map<String, Object>>();
  	}
  
  	/**
  	 * Create a new GeneratedKeyHolder with a given list.
  	 * @param keyList a list to hold maps of keys
  	 */
  	public GeneratedKeyHolder(List<Map<String, Object>> keyList) {
  		this.keyList = keyList;
  	}
  
  
  	@Override
  	public Number getKey() throws InvalidDataAccessApiUsageException, DataRetrievalFailureException {
  		if (this.keyList.size() == 0) {
  			return null;
  		}
  		if (this.keyList.size() > 1 || 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<Object> keyIter = 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 != null ? key.getClass().getName() : null) +
  						"] 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.");
  		}
  	}
  
  	@Override
  	public Map<String, Object> 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 this.keyList.get(0);
  	}
  
  	@Override
 	public List<Map<String, Object>> getKeyList() {
 		return this.keyList;
 	}
 
 }