/*
    * Copyright 2001-2008 The Apache Software Foundation.
    * 
    * 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.apache.juddi.query;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.UUID;
  
  import javax.persistence.EntityManager;
  
  import org.apache.commons.configuration.ConfigurationException;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.juddi.config.AppConfig;
  import org.apache.juddi.config.Property;
  import org.apache.juddi.query.util.DynamicQuery;
  import org.apache.juddi.query.util.FindQualifiers;
  import org.uddi.v3_service.DispositionReportFaultMessage;
  import org.uddi.api_v3.ListDescription;
  
  /**
   * The "select" method retrieves all the entities for the input key list and sorts according to the user settings.  Paging is taken into account when retrieving 
   * the results.  The result is a list of the entity objects containing all top level elements (restricted to the given page). 
   * 
   * NOTE:  Results usually need multiple one-to-many collections to be fetched.  Although this could be done in one query with eager fetching, this strategy is not
   * recommended as it will lead to a potentially large Cartesian product.  Therefore, the collections are initialized in separate queries during the mapping 
   * stage.  If the returned results are small (maxRows parameters is set appropriately), a single query is likely faster, but probably not by enough to consider 
   * the optimization under these conditions.
   * 
   * @author <a href="mailto:jfaath@apache.org">Jeff Faath</a>
   */
  public class FetchBindingTemplatesQuery extends BindingTemplateQuery {
  
  	private static final Log log = LogFactory.getLog(FetchBindingTemplatesQuery.class);
  
  	protected static final String selectSQL;
  
  	static {
  		StringBuilder sql = new StringBuilder(200);
  		sql.append("select " + ENTITY_ALIAS + " from " + ENTITY_NAME + " " + ENTITY_ALIAS + " ");
  		selectSQL = sql.toString();
  	}
  	
  	public static List<?> select(EntityManager em, FindQualifiers fq, List<?> keysIn, Integer maxRowsUser, Integer listHead, ListDescription listDesc, DynamicQuery.Parameter... restrictions) throws DispositionReportFaultMessage {
  		
  		// If keysIn is null or empty, then nothing to fetch.
  		if ((keysIn == null) || (keysIn.size() == 0))
  			return Collections.emptyList();
  		int maxRows = DEFAULT_MAXROWS;
  		try {
  			maxRows = AppConfig.getConfiguration().getInteger(Property.JUDDI_MAX_ROWS, DEFAULT_MAXROWS);
  		}
  		catch(ConfigurationException ce) {
  			log.error("Configuration exception occurred retrieving: " + Property.JUDDI_MAX_ROWS);
  		}
  		DynamicQuery dynamicQry = new DynamicQuery(selectSQL);
  		if (keysIn.size() > maxRows) {
  			UUID uuid = UUID.randomUUID();
  			storeIntermediateKeySetResults(em, uuid.toString(), keysIn);
  			appendTempTable(dynamicQry);
  			appendSortTables(dynamicQry);
  			appendTempJoin(dynamicQry, uuid.toString());
  		}
  		else {
  			appendSortTables(dynamicQry);
  			dynamicQry.appendInListWithAnd(ENTITY_ALIAS + "." + KEY_NAME, keysIn);
  		}
  		if (restrictions != null && restrictions.length > 0)
  			dynamicQry.AND().pad().appendGroupedAnd(restrictions);
  		
  		appendSortCriteria(dynamicQry, fq);
  
  		log.debug(dynamicQry);
  		
  		return getPagedResult(em, dynamicQry, maxRowsUser, listHead, listDesc);
  	}
  	
  	private static void appendTempTable(DynamicQuery qry) {
  		qry.comma().append(TEMP_ENTITY_NAME + " " +  TEMP_ENTITY_ALIAS );
  	}
  	
  	private static void appendTempJoin(DynamicQuery qry, String uuid) {
  		qry.pad().AND().pad().append(TEMP_ENTITY_PK_KEY_NAME).append(DynamicQuery.PREDICATE_EQUALS);
  		qry.pad().append(ENTITY_ALIAS + "." + KEY_NAME);
 		qry.pad().AND().pad().append(TEMP_ENTITY_PK_TXID_NAME).append(DynamicQuery.PREDICATE_EQUALS);
 		qry.append("'" + uuid + "'").pad();
 	}
 	
 	private static void appendSortTables(DynamicQuery qry) {
 		// BindingTemplates can only be sorted by date.
 		qry.WHERE().pad().append("1=1").pad();
 	}
 	
 	/*
 	 *	BindingTemplates can only be sorted by date.
 	 */
 	private static void appendSortCriteria(DynamicQuery qry, FindQualifiers fq) {
 		
 		qry.ORDERBY().pad();
 		
 		if (fq.isSortByDateAsc())
 			qry.append(ENTITY_ALIAS + ".modified").pad().append(DynamicQuery.SORT_ASC);
 		else
 			qry.append(ENTITY_ALIAS + ".modified").pad().append(DynamicQuery.SORT_DESC);
 		
 		qry.pad();
 		
 	}
 
 }