/*
* This program is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
* Foundation.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* or from the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* 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 Lesser General Public License for more details.
*
* Copyright (c) 2001 - 2009 Object Refinery Ltd, Pentaho Corporation and Contributors.. All rights reserved.
*/
package org.pentaho.reporting.engine.classic.core.function;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.pentaho.reporting.engine.classic.core.Group;
import org.pentaho.reporting.engine.classic.core.event.ReportEvent;
/**
* A report function that calculates the minimum value of one field (column) from the data-row. The function can be used
* in two ways: <ul> <li>to calculate a minimum value for the entire report;</li> <li>to calculate a minimum value
* within a particular group;</li> </ul> This function expects its input values to be either java.lang.Number instances
* or Strings that can be parsed to java.lang.Number instances using a java.text.DecimalFormat.
* <p/>
* The function undestands two parameters, the <code>field</code> parameter is required and denotes the name of an
* ItemBand-field which gets summed up.
* <p/>
* The parameter <code>group</code> denotes the name of a group. When this group is started, the counter gets reseted to
* null.
*
* @author Thomas Morgner
*/
public class ItemMinFunction extends AbstractFunction implements FieldAggregationFunction
{
private static final Log logger = LogFactory.getLog(ItemMinFunction.class);
/**
* The minimum value.
*/
private transient Comparable min;
/**
* The name of the group on which to reset the count. This can be set to null to compute the minimum for the whole
* report.
*/
private String group;
/**
* The name of the field from where to read the values.
*/
private String field;
/**
* Constructs an unnamed function. Make sure to set a Name or function initialisation will fail.
*/
public ItemMinFunction()
{
min = null;
}
/**
* Constructs a named function. <P> The field must be defined before using the function.
*
* @param name The function name.
*/
public ItemMinFunction(final String name)
{
this();
setName(name);
}
/**
* Receives notification that a new report is about to start. <P> Does nothing.
*
* @param event Information about the event.
*/
public void reportInitialized(final ReportEvent event)
{
this.min = null;
}
/**
* Receives notification that a new group is about to start. If this is the group defined for the function, then the
* minimum value is reset to zero.
*
* @param event Information about the event.
*/
public void groupStarted(final ReportEvent event)
{
final String mygroup = getGroup();
if (mygroup == null)
{
return;
}
final Group group = event.getReport().getGroup(event.getState().getCurrentGroupIndex());
if (getGroup().equals(group.getName()))
{
this.min = null;
}
}
/**
* Returns the group name.
*
* @return The group name.
*/
public String getGroup()
{
return group;
}
/**
* Sets the group name. <P> If a group is defined, the minimum value is reset to zero at the start of every instance
* of this group.
*
* @param name the group name (null permitted).
*/
public void setGroup(final String name)
{
this.group = name;
}
/**
* Returns the field used by the function. The field name corresponds to a column name in the report's data-row.
*
* @return The field name.
*/
public String getField()
{
return field;
}
/**
* Sets the field name for the function. The field name corresponds to a column name in the report's data-row.
*
* @param field the field name.
*/
public void setField(final String field)
{
this.field = field;
}
/**
* Receives notification that a row of data is being processed. Reads the data from the field defined for this
* function and calculates the minimum value.
*
* @param event Information about the event.
*/
public void itemsAdvanced(final ReportEvent event)
{
final Object fieldValue = event.getDataRow().get(getField());
if (fieldValue instanceof Comparable == false)
{
return;
}
try
{
final Comparable compare = (Comparable) fieldValue;
if (min == null)
{
min = compare;
}
else if (min.compareTo(compare) > 0)
{
min = compare;
}
}
catch (Exception e)
{
ItemMinFunction.logger.error("ItemMinFunction.advanceItems(): problem adding number.");
}
}
/**
* Returns the function value, in this case the running total of a specific column in the report's data row.
*
* @return The function value.
*/
public Object getValue()
{
return min;
}
/**
* Return a completly separated copy of this function. The copy does no longer share any changeable objects with the
* original function.
*
* @return a copy of this function.
*/
public Expression getInstance()
{
final ItemMinFunction function = (ItemMinFunction) super.getInstance();
function.min = null;
return function;
}
}