/*
    * Copyright (C) 2003-2013 eXo Platform SAS.
    *
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Affero General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
    * This program 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 Affero General Public License for more details.
   *
   * You should have received a copy of the GNU Affero General Public License
   * along with this program. If not, see <http://www.gnu.org/licenses/>.
   */
  package org.exoplatform.services.wcm.search.base;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import javax.jcr.NodeIterator;
  import javax.jcr.Session;
  import javax.jcr.query.Query;
  import javax.jcr.query.QueryResult;
  import javax.jcr.query.RowIterator;
  
  import org.exoplatform.commons.utils.PageList;
  import org.exoplatform.services.jcr.ext.common.SessionProvider;
  import org.exoplatform.services.jcr.impl.core.query.QueryImpl;
  import org.exoplatform.services.jcr.impl.core.query.lucene.QueryResultImpl;
  import org.exoplatform.services.log.ExoLogger;
  import org.exoplatform.services.log.Log;
  import org.exoplatform.services.wcm.utils.WCMCoreUtils;
  
  /**
   * This class works as a page list but only load 1 page data at a time.
   * Created by The eXo Platform SAS
   * Author : eXoPlatform
   *          exo@exoplatform.com
   * Oct 4, 2013  
   */
  public class LazyPageList<E> extends PageList{
    
    /** the log */
    private static final Log LOG  = ExoLogger.getLogger(LazyPageList.class.getName());
    /** the query data */
    private QueryData queryData_;
    /** the data creator that creates data from search result */
    private SearchDataCreator<E> dataCreator_;
    /** total size */
    private int total_;
    /** item per page */
    private int pageSize_;
    
    public LazyPageList(QueryData queryData, int pageSize, SearchDataCreator<E> dataCreator) {
      super(pageSize);
      queryData_ = queryData.clone();
      dataCreator_ = dataCreator;
      pageSize_ = pageSize;
      total_ = 0;
      //get total amount
      if (queryData.getQueryStatement() != null) {
        try {
          SessionProvider provider = WCMCoreUtils.getUserSessionProvider();
          Session session = provider.getSession(queryData.getWorkSpace(), WCMCoreUtils.getRepository());
          //In JCR, For performances reason, the permissions are not checked when
          // the order is set in the query. In order to take the permissions in consideration,
          // We need to suppress the orderBy from the Query statement
          String querySizeStatement = queryData.getQueryStatement();
          if (querySizeStatement.indexOf("ORDER BY") > 0) {
            querySizeStatement = querySizeStatement.substring(0,querySizeStatement.indexOf("ORDER BY"));
          }
          total_ = (int)session.getWorkspace().getQueryManager().
          createQuery(querySizeStatement, queryData.getLanguage_()).execute().getRows().getSize();
        } catch (Exception e) {
          if (LOG.isErrorEnabled()) {
            LOG.error("Can not execute the query: " + queryData.getQueryStatement(), e);
          }
        }
      }
      setAvailablePage(total_);
    }
  
    @Override
    protected void populateCurrentPage(int page) throws Exception {
      currentListPage_ = new ArrayList<E>();
      if (queryData_.getQueryStatement() != null) {
        try {
          SessionProvider provider = WCMCoreUtils.getSystemSessionProvider();
          Session session = provider.getSession(queryData_.getWorkSpace(), WCMCoreUtils.getRepository());
          Query query = session.getWorkspace().getQueryManager().
          createQuery(queryData_.getQueryStatement(), queryData_.getLanguage_());
          ((QueryImpl)query).setOffset((page-1)*pageSize_);
          ((QueryImpl)query).setLimit(pageSize_);
          ((QueryImpl)query).setCaseInsensitiveOrder(true);
          QueryResult ret = query.execute();
          
          NodeIterator iter = ret.getNodes();
         RowIterator rowIter = ret.getRows();
         while (iter.hasNext()) {
           currentListPage_.add(dataCreator_.createData(iter.nextNode(), rowIter.nextRow(), null));
         }
       } catch (Exception e) {
         if (LOG.isErrorEnabled()) {
           LOG.error("Can not execute the query: " + queryData_.getQueryStatement(), e);
         }
       }
     }
   }
 
   @Override
   public List<E> getAll() throws Exception {
     return new ArrayList<E>();
   }
 
 }