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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;

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

import nz.co.senanque.validationengine.ValidationObject;

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

/**
 * 
 * This describes an instance of a rule, ie where a rule applies to a specific object.
 * 
 * @author Roger Parkinson
 * @version $Revision: 1.5 $
 */
public class RuleContext implements Serializable
{
	private static final long serialVersionUID = 1L;
	private static final Logger log = LoggerFactory.getLogger(RuleContext.class);
    private final transient Rule m_rule;
    private final transient RuleSession m_ruleSession;
    private final transient Indenter m_indenter;
    private final transient ValidationObject m_validationObject;
    public ValidationObject getValidationObject() {
		return m_validationObject;
	}
	private transient Set m_excludes = null;
    private Set m_activates = null;
    private Set m_requireds = null;
    private Set m_assigns = null;
    private Set m_readOnlys;
    protected static String getKey(final Rule rule, final ValidationObject validationObject)
    {
        return rule.getRuleName()+":"+System.identityHashCode(validationObject);
    }
    protected String getKey()
    {
        return getKey(m_rule,m_validationObject);
    }

    public RuleContext(final Rule rule, final RuleSession session, final Indenter indenter,
            final ValidationObject validationObject)
    {
        m_rule = rule;
        m_ruleSession = session;
        m_indenter = indenter;
        m_validationObject = validationObject;
    }

    public void fire()
    {
        log.debug("{} firing {}", m_indenter, this);
        m_indenter.increment();
        boolean b = false;
        try
        {
            m_rule.evaluate(m_ruleSession, m_validationObject,this);
        }
        catch (ConstraintViolationException e)
        {
            if (!m_ruleSession.isUnbinding(m_validationObject)) {
            	b = false;
                m_indenter.decrement();
                log.debug("{} completed firing {} result: {} {}", new Object[]{ m_indenter, this, b, e.getMessage() });
                e.setRule(m_rule);
                throw e;
            }
        }
        catch (InferenceException e)
        {
            b = false;
            m_indenter.decrement();
            log.debug("{} completed firing {} result: {} {}", new Object[]{ m_indenter, this, b, e.getMessage() });
            ConstraintViolationException e1 = new ConstraintViolationException(m_rule.getMessage(m_ruleSession,m_validationObject),e);
            e1.setRule(m_rule);
            throw e1;
        }
        m_indenter.decrement();
        log.debug("{} completed firing {}", new Object[]{ m_indenter, this });
    }

    public void reset()
    {
        log.debug("{}resetting {}", m_indenter, this);
        m_indenter.increment();
        clearExcludes();
        clearActivates();
        clearAssigns();
        clearReadOnlys();
        clearRequireds();
        m_indenter.decrement();
        log.debug("{}completed resetting {}", m_indenter, this);
    }

    private void clearActivates()
    {
        if (m_activates == null)
        {
            return;
        }
        for (RuleProxyField ruleProxyField : m_activates)
        {
            ruleProxyField.setInActive(true);
        }
        m_activates.clear();
    }

    private void clearReadOnlys()
    {
        if (m_readOnlys == null)
        {
            return;
        }
        for (RuleProxyField ruleProxyField : m_readOnlys)
        {
            ruleProxyField.setReadOnly(false);
        }
        m_readOnlys.clear();
    }

    private void clearRequireds()
    {
        if (m_requireds == null)
        {
            return;
        }
        for (RuleProxyField ruleProxyField : m_requireds)
        {
            ruleProxyField.setRequired(false);
        }
        m_requireds.clear();
    }

    private void clearExcludes()
    {
        if (m_excludes == null)
        {
            return;
        }
        for (Exclude exclude : m_excludes)
        {
            exclude.getProxyField().clearExclude(exclude.getKey());
        }
        m_excludes.clear();
    }

    private void clearAssigns()
    {
        if (m_assigns == null)
        {
            log.debug("{}No assigns",m_indenter);
            return;
        }
        for (RuleProxyField ruleProxyField : m_assigns)
        {
            ruleProxyField.reset();
        }
        m_assigns.clear();
    }

    public Rule getRule()
    {
        return m_rule;
    }
    public String toString()
    {
        return "Rule: "+m_rule.toString();
    }
    public void addAssign(RuleProxyField proxyField)
    {
        if (m_assigns == null)
        {
            m_assigns = new HashSet();
        }
        m_assigns.add(proxyField);        
    }
    public void addReadOnly(RuleProxyField proxyField)
    {
        if (m_readOnlys == null)
        {
            m_readOnlys = new HashSet();
        }
        m_readOnlys.add(proxyField);        
    }
    public void addActivate(RuleProxyField proxyField)
    {
        if (m_activates == null)
        {
            m_activates = new HashSet();
        }
        m_activates.add(proxyField);        
   }
    public void addRequired(RuleProxyField proxyField)
    {
        if (m_requireds == null)
        {
            m_requireds = new HashSet();
        }
        m_requireds.add(proxyField);        
    }
    public void addExclude(Exclude exclude)
    {
        if (m_excludes == null)
        {
            m_excludes = new HashSet();
        }
        m_excludes.add(exclude);        
    }
	public Set getAllRuleProxyFields() {
		Set ret = new HashSet();
		if (m_activates != null)
		{
			ret.addAll(m_activates);
		}
		if (m_requireds != null)
		{
			ret.addAll(m_requireds);
		}
		if (m_assigns != null)
		{
			ret.addAll(m_assigns);
		}
		if (m_readOnlys != null)
		{
			ret.addAll(m_readOnlys);
		}
		return ret;
	}

}