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This is a plugin to Madura Objects. It provides a rules/constraint engine to assist with validation, deriving new values from user inputs (eg total of invoices entered on this customer) an manipulating metadata (eg because the amount is above X we make some field readonly). Note that the Java that is using the monitored objects is quite unaware of the rules layer implemented here. That means you can change rules without having to go back to your Java code, and it also means you don't have to wonder if everything implemented the same rules. Anything using that Java object has the rules (unless you turn them all off).

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/*******************************************************************************
 * Copyright (c)2014 Prometheus Consulting
 *
 * 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 nz.co.senanque.rules.decisiontable;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

import nz.co.senanque.rules.FieldReference;
import nz.co.senanque.rules.Rule;
import nz.co.senanque.rules.RuleContext;
import nz.co.senanque.rules.RuleSession;
import nz.co.senanque.validationengine.ProxyField;
import nz.co.senanque.validationengine.ValidationObject;
import nz.co.senanque.validationengine.ValidationUtils;
import nz.co.senanque.validationengine.choicelists.ChoiceBase;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 
 * The generated decision table rules all extend this
 * Table cells may be null to represent any value. 
 * If a proxy value has not yet been assigned it is ignored.
 * 
 * @author Roger Parkinson
 * @version $Revision: 1.3 $
 */
public abstract class AbstractDecisionTable implements Rule, Serializable
{
    private static final long serialVersionUID = 1L;
	private static Logger logger = LoggerFactory.getLogger(AbstractDecisionTable.class);
    private transient String[] m_columnNames;
    private transient Row[] m_rows;
    private transient boolean[] m_autoAssign;
    
    protected ProxyField getProxyField(RuleSession session, ValidationObject object, String fieldName)
    {
        return session.getMetadata(object).getProxyField(fieldName);
    }

    public void evaluate(final RuleSession session, final ValidationObject object,
            final RuleContext ruleContext)
    {
        final int columnCount = m_columnNames.length;
        ProxyField[] proxyFields = new ProxyField[columnCount];
        Object[] values = new Object[columnCount];
        
        ProxyField lastProxyField = session.getLastProxyField();
        @SuppressWarnings("unused")
		int columnLastEntered = -1;
        for (int i=0;i[] valids = figureValids(columnCount,values);
        for (int columnIndex=0; columnIndex < columnCount; columnIndex++)
        {
            if (values[columnIndex]==null)
            {
                continue;
            }
            Object value = values[columnIndex];
            values[columnIndex] =  null;
            Set[] valids1 = figureValids(columnCount,values);
            if (valids1[columnIndex] != null)
            {
	            try {
	                if (valids[columnIndex] == null)
	                {
	                	valids[columnIndex] = new HashSet();
	                }
	        		valids[columnIndex].addAll(valids1[columnIndex]);
				} catch (NullPointerException e) {
					e.printStackTrace();
				}
            }
            values[columnIndex] = value;
        }
        if (logger.isDebugEnabled())
        {
            debugDump("before", columnCount,proxyFields,values);
        }
        
        for (int columnIndex=0; columnIndex < columnCount; columnIndex++)
        {
            if (valids[columnIndex]==null)
            {
                continue;
            }
            Set validsList = valids[columnIndex];
            for (ChoiceBase choiceBase: proxyFields[columnIndex].getChoiceList())
            {
                if (!validsList.contains(choiceBase.getKey().toString()))
                {
                    session.exclude(session.getRuleProxyField(proxyFields[columnIndex]), choiceBase.getKey().toString(), ruleContext);
                }
            }
            if (m_autoAssign[columnIndex])
            {
                session.autoAssign(proxyFields[columnIndex],ruleContext);
            }
        }
        if (logger.isDebugEnabled())
        {
            debugDump("after", columnCount,proxyFields,values);
        }
    }
    private void debugDump(String comment, int columnCount, ProxyField[] proxyFields, Object[] values)
    {
        logger.debug("-----------{}",comment);
        for (int columnIndex=0; columnIndex < columnCount; columnIndex++)
        {
            logger.debug("\tfield {} \tcurrent {} \tvalids {}",new Object[]{proxyFields[columnIndex].getFieldName(),values[columnIndex],proxyFields[columnIndex].getChoiceList()});
        }
        logger.debug("---------end {}",comment);

    }
    private Set[] figureValids(int columnCount,Object[] values)
    {
        @SuppressWarnings("unchecked")
		Set[] valids = new Set[columnCount];
        for (Row row : m_rows)
        {
            boolean excludeRow = false;
            final Column[] columns = row.getColumns();
            for (int i = 0; i < columnCount; i++)
            {
                if (values[i] != null
                        && columns[i] != null
                        && (!ValidationUtils.equals(values[i], columns[i]
                                .getValue())))
                {
                    // We have a value on this property so we can use it to
                    // exclude.
                    excludeRow = true;
                    break;
                }
            }
            if (!excludeRow)
            {
                // this row has either nulls or valid values so record them.
                for (int i = 0; i < columnCount; i++)
                {
                    String value = columns[i].getValue();
                    if (value != null)
                    {
                        addValid(valids, i, value);
                    }
                }
            }
        }
        return valids;
    }
    public void addValid(Set[] valids, int i, String value)
    {
        if (valids[i] == null)
        {
            valids[i] = new HashSet();
        }
        Set v = (Set)valids[i];
        if (v.contains(value))
        {
            return;
        }
        v.add(value);
    }

    public FieldReference[] updaters()
    {
        return null;
    }

    protected String[] getColumnNames()
    {
        return m_columnNames.clone();
    }

    protected void setColumnNames(String[] columnNames)
    {
        m_columnNames = columnNames.clone();
    }
    protected void setRows(Row[] rows)
    {
        m_rows = rows.clone();        
    }

    public void setAutoAssign(boolean[] autoAssign)
    {
        m_autoAssign = autoAssign.clone();
    }
    public FieldReference[] outputs() {
    	return null;
    }
}