/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.cocoon.forms.formmodel.algorithms;
import java.math.BigDecimal;
import java.util.Collection;
import java.util.Iterator;
import org.apache.avalon.framework.CascadingError;
import org.apache.cocoon.forms.datatype.Datatype;
import org.apache.cocoon.forms.formmodel.CannotYetResolveWarning;
import org.apache.cocoon.forms.formmodel.ExpressionContextImpl;
import org.apache.cocoon.forms.formmodel.Form;
import org.apache.cocoon.forms.formmodel.Widget;
import org.apache.cocoon.forms.util.WidgetFinder;
import org.outerj.expression.Expression;
import org.outerj.expression.ExpressionException;
/**
* An xreporter {@link org.outerj.expression.Expression} based algorithm that repeats the formula on a
* set of fields.
*
* <p>
* The specified formula will be applied iterating on the specified widgets. The final result will be the result of the
* last iteration. From inside the formula you can access this two extra variables :
* <dl>
* <dt>formulaResult</dt>
* <dd>The result of the previous iteration, or the result of the initial result if this is the first iteration.</dd>
* <dt>formulaCurrent</dt>
* <dd>The value of the current trigger widget.</dd>
* </dl>
* </p>
* <p>
* The initial result is evaluated before starting the iteration, and its value is used as a formulaResult for the
* first iteration.
* </p>
* <p>
* It's possible to define nearly every cyclic arithmetic operation with this algorithm, for example :
* <dl>
* <dt>Sum</dt>
* <dd>initial-result="0" formula="formulaResult + formulaCurrent"</dd>
* <dt>Multiplication</dt>
* <dd>initial-result="1" formula="formulaResult * formulaCurrent"</dd>
* </dl>
* </p>
* <p>
* More over, thru the use of advanced xreporter syntax it's possible to quickly implement also complex
* algorithms:
* <ul>
* <li>Count all items with a price higher than 100 : eval="formulaResult + If(price > 100, 1, 0)"
* (read : the result is the previous result plus one if price is over 100, 0 if price is less than 100)</li>
* <li>Obtain a sum of all movements, wether they are positive or negative amount movements :
* eval="formulaResult + Abs(amount)"</li>
* <li>Count how many slots are empty in the 10 items box you are using for packaging :
* eval="formulaResult + Reminder(items, 10)"
* </ul>
* </p>
* <p>
* Note: please take care that xreporter expressions are not that accurate when it comes to decimals. The default
* divide operator rounds the result, see http://issues.cocoondev.org/browse/XRP-115. Also consider that the
* available set of functions can be expanded implementing and using new ones. Please see
* <a href="http://outerthought.net/wqm/xreporter/en/expressions.html">
* http://outerthought.net/wqm/xreporter/en/expressions.html</a> for an overview of xreportes expressions and
* {@link org.apache.cocoon.forms.expression.IsNullFunction} or
* {@link org.apache.cocoon.forms.expression.StringFunction}
* for examples of custom xreporter functions.
* </p>
* @version $Id$
*/
public class RepeatedFormula extends SimpleFormula {
private Expression initialResult = null;
private String repeatOn = null;
public Object calculate(Form form, Widget parent, Datatype datatype) {
try {
Object result = null;
if (initialResult != null) {
result = initialResult.evaluate(new ExpressionContextImpl(parent, true));
}
WidgetFinder finder = new WidgetFinder(parent, this.repeatOn, false);
Collection widgets = finder.getWidgets();
for (Iterator iter = widgets.iterator(); iter.hasNext();) {
Widget widget = (Widget) iter.next();
ResultExpressionContext ctx = new ResultExpressionContext(widget, result);
result = formula.evaluate(ctx);
}
return result;
} catch (CannotYetResolveWarning w) {
return null;
} catch (ExpressionException e) {
throw new CascadingError("Error evaluating calculated field formula", e);
}
}
static class ResultExpressionContext extends ExpressionContextImpl {
Object result = null;
Widget current = null;
public ResultExpressionContext(Widget widget, Object result) {
super(widget.getParent(), true);
current = widget;
this.result = result;
}
public Object resolveVariable(String name) {
if (name.equals("formulaResult")) {
return result;
}
if (name.equals("formulaCurrent")) {
Object value = current.getValue();
if (value == null && current.isRequired()) {
throw new CannotYetResolveWarning();
}
if (value instanceof Long)
return new BigDecimal(((Long)value).longValue());
else if (value instanceof Integer)
return new BigDecimal(((Integer)value).intValue());
else
return value;
}
return super.resolveVariable(name);
}
}
/**
* @return Returns the initialResult.
*/
public Expression getInitialResult() {
return initialResult;
}
/**
* @param initialResult The initialResult to set.
*/
public void setInitialResult(Expression initialResult) {
this.initialResult = initialResult;
}
/**
* @return Returns the iterateOn.
*/
public String getRepeatOn() {
return repeatOn;
}
/**
* @param iterateOn The iterateOn to set.
*/
public void setRepeatOn(String iterateOn) {
this.repeatOn = iterateOn;
}
}