package org.apache.torque.util;
   
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  import org.apache.commons.lang.StringUtils;
  
  /***
   * Used to assemble an SQL SELECT query.  Attributes exist for the
   * sections of a SELECT: modifiers, columns, from clause, where
   * clause, and order by clause.  The various parts of the query are
   * appended to buffers which only accept unique entries.  This class
   * is used primarily by BasePeer.
   *
   * @author <a href="mailto:jmcnally@collab.net">John D. McNally</a>
   * @author <a href="mailto:sam@neurogrid.com">Sam Joseph</a>
   * @author <a href="mailto:mpoeschl@marmot.at">Martin Poeschl</a>
   * @version $Id: Query.java,v 1.12 2003/03/24 21:53:42 mpoeschl Exp $
   */
  public class Query
  {
      private static final String SELECT = "SELECT ";
      private static final String FROM = " FROM ";
      private static final String WHERE = " WHERE ";
      private static final String AND = " AND ";
      private static final String ORDER_BY = " ORDER BY ";
      private static final String GROUP_BY = " GROUP BY ";
      private static final String HAVING = " HAVING ";
      private static final String LIMIT = " LIMIT ";
      private static final String ROWCOUNT = " SET ROWCOUNT ";
  
      private UniqueList selectModifiers = new UniqueList();
      private UniqueList selectColumns = new UniqueList();
      private UniqueList fromTables = new UniqueList();
      private UniqueList whereCriteria = new UniqueList();
      private UniqueList orderByColumns = new UniqueList();
      private UniqueList groupByColumns = new UniqueList();
      private String having;
      private String limit;
      private String rowcount;
  
      /***
       * Retrieve the modifier buffer in order to add modifiers to this
       * query.  E.g. DISTINCT and ALL.
       *
       * @return An UniqueList used to add modifiers.
       */
      public UniqueList getSelectModifiers()
     {
         return selectModifiers;
     }
 
     /***
      * Set the modifiers. E.g. DISTINCT and ALL.
      *
      * @param modifiers the modifiers
      */
     public void setSelectModifiers(UniqueList modifiers)
     {
         selectModifiers = modifiers;
     }
 
     /***
      * Retrieve the columns buffer in order to specify which columns
      * are returned in this query.
      *
      *
      * @return An UniqueList used to add columns to be selected.
      */
     public UniqueList getSelectClause()
     {
         return selectColumns;
     }
 
     /***
      * Set the columns.
      *
      * @param columns columns list
      */
     public void setSelectClause(UniqueList columns)
     {
         selectColumns = columns;
     }
 
     /***
      * Retrieve the from buffer in order to specify which tables are
      * involved in this query.
      *
      * @return An UniqueList used to add tables involved in the query.
      */
     public UniqueList getFromClause()
     {
         return fromTables;
     }
 
     /***
      * Set the from clause.
      *
      * @param tables the tables
      */
     public void setFromClause(UniqueList tables)
     {
         fromTables = tables;
     }
 
     /***
      * Retrieve the where buffer in order to specify the selection
      * criteria E.g. column_a=3.  Expressions added to the buffer will
      * be separated using AND.
      *
      * @return An UniqueList used to add selection criteria.
      */
     public UniqueList getWhereClause()
     {
         return whereCriteria;
     }
 
     /***
      * Set the where clause.
      *
      * @param where where clause
      */
     public void setWhereClause(UniqueList where)
     {
         whereCriteria = where;
     }
 
     /***
      * Retrieve the order by columns buffer in order to specify which
      * columns are used to sort the results of the query.
      *
      * @return An UniqueList used to add columns to sort on.
      */
     public UniqueList getOrderByClause()
     {
         return orderByColumns;
     }
 
     /***
      * Retrieve the group by columns buffer in order to specify which
      * columns are used to group the results of the query.
      *
      * @return An UniqueList used to add columns to group on.
      */
     public UniqueList getGroupByClause()
     {
         return groupByColumns;
     }
 
     /***
      * Set the having clause.  This is used to restrict which rows
      * are returned.
      *
      * @param having A String.
      */
     public void setHaving(String having)
     {
         this.having = having;
     }
 
     /***
      * Set the limit number.  This is used to limit the number of rows
      * returned by a query, and the row where the resultset starts.
      *
      * @param limit A String.
      */
     public void setLimit(String limit)
     {
         this.limit = limit;
     }
 
     /***
      * Set the rowcount number.  This is used to limit the number of
      * rows returned by Sybase and MS SQL/Server.
      *
      * @param rowcount A String.
      */
     public void setRowcount(String rowcount)
     {
         this.rowcount = rowcount;
     }
 
     /***
      * Get the having clause.  This is used to restrict which
      * rows are returned based on some condition.
      *
      * @return A String that is the having clause.
      */
     public String getHaving()
     {
         return having;
     }
 
     /***
      * Get the limit number.  This is used to limit the number of
      * returned by a query in Postgres.
      *
      * @return A String with the limit.
      */
     public String getLimit()
     {
         return limit;
     }
 
     /***
      * Get the rowcount number.  This is used to limit the number of
      * returned by a query in Sybase and MS SQL/Server.
      *
      * @return A String with the row count.
      */
     public String getRowcount()
     {
         return rowcount;
     }
 
     /***
      * Outputs the query statement.
      *
      * @return A String with the query statement.
      */
     public String toString()
     {
         StringBuffer stmt = new StringBuffer();
         if (rowcount != null)
         {
             stmt.append(ROWCOUNT)
                 .append(rowcount)
                 .append(" ");
         }
         stmt.append(SELECT)
             .append(StringUtils.join(selectModifiers.iterator(), " "))
             .append(StringUtils.join(selectColumns.iterator(), ", "))
             .append(FROM)
             .append(StringUtils.join(fromTables.iterator(), ", "));
         if (!whereCriteria.isEmpty())
         {
             stmt.append(WHERE)
                 .append(StringUtils.join(whereCriteria.iterator(), AND));
         }
         if (!groupByColumns.isEmpty())
         {
             stmt.append(GROUP_BY)
                 .append(StringUtils.join(groupByColumns.iterator(), ", "));
         }
         if (having != null)
         {
             stmt.append(HAVING)
                 .append(having);
         }
         if (!orderByColumns.isEmpty())
         {
             stmt.append(ORDER_BY)
                 .append(StringUtils.join(orderByColumns.iterator(), ", "));
         }
         if (limit != null)
         {
             stmt.append(LIMIT)
                 .append(limit);
         }
         if (rowcount != null)
         {
             stmt.append(ROWCOUNT)
                 .append("0");
         }
         return stmt.toString();
     }
 }