package org.apache.commons.digester3.xmlrules;

/*
 * 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.
 */

import java.net.MalformedURLException;
import java.net.URL;

import org.apache.commons.digester3.Rule;
import org.apache.commons.digester3.binder.RulesBinder;
import org.apache.commons.digester3.binder.RulesModule;
import org.xml.sax.Attributes;

A rule for including one rules XML file within another. Included files behave as if they are 'macro-expanded' within
the includer. This means that the values of the pattern stack are prefixed to every pattern in the included rules.

This rule will detect 'circular' includes, which would result in infinite recursion. It throws a
CircularIncludeException when a cycle is detected, which will terminate the parse.
/**
 * A rule for including one rules XML file within another. Included files behave as if they are 'macro-expanded' within
 * the includer. This means that the values of the pattern stack are prefixed to every pattern in the included rules.
 * <p>
 * This rule will detect 'circular' includes, which would result in infinite recursion. It throws a
 * CircularIncludeException when a cycle is detected, which will terminate the parse.
 */
final class IncludeRule
    extends Rule
{

    private static final String CLASSPATH_URL_PREFIX = "classpath:";

    private final WithMemoryRulesBinder memoryRulesBinder;

    private final RulesBinder targetRulesBinder;

    public IncludeRule( final WithMemoryRulesBinder memoryRulesBinder, final RulesBinder targetRulesBinder )
    {
        this.memoryRulesBinder = memoryRulesBinder;
        this.targetRulesBinder = targetRulesBinder;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public void begin( String namespace, String name, Attributes attributes )
        throws Exception
    {
        // The path attribute gives the URI to another digester rules xml file
        String fileName = attributes.getValue( "url" );
        if ( fileName != null && fileName.length() > 0 )
        {
            final URL xmlRulesResource;

            if ( fileName.startsWith( CLASSPATH_URL_PREFIX ) )
            {
                String path = fileName.substring( CLASSPATH_URL_PREFIX.length() );
                if ( '/' == path.charAt( 0 ) )
                {
                    path = path.substring( 1 );
                }
                xmlRulesResource = this.targetRulesBinder.getContextClassLoader().getResource( path );
                if ( xmlRulesResource == null )
                {
                    targetRulesBinder.addError( "Resource '%s' not found, please make sure it is in the classpath",
                                                path );
                    return;
                }
            }
            else
            {
                try
                {
                    xmlRulesResource = new URL( fileName );
                }
                catch ( MalformedURLException e )
                {
                    targetRulesBinder.addError( "An error occurred while inculing file from '%s': %s", fileName,
                                                e.getMessage() );
                    return;
                }
            }

            if ( memoryRulesBinder.getIncludedFiles().add( xmlRulesResource.toString() ) )
            {
                install( new FromXmlRulesModule()
                {

                    @Override
                    protected void loadRules()
                    {
                        loadXMLRules( xmlRulesResource );
                    }

                } );
            }
            else
            {
                targetRulesBinder.addError( "Circular file inclusion detected for XML rules: %s", xmlRulesResource );
            }
        }

        // The class attribute gives the name of a class that implements
        // the DigesterRulesSource interface
        String className = attributes.getValue( "class" );
        if ( className != null && className.length() > 0 )
        {
            try
            {
                Class<?> cls = Class.forName( className );
                if ( !RulesModule.class.isAssignableFrom( cls ) )
                {
                    targetRulesBinder.addError( "Class '%s' if not a '%s' implementation", className,
                                                RulesModule.class.getName() );
                    return;
                }

                RulesModule rulesSource = (RulesModule) cls.newInstance();

                install( rulesSource );
            }
            catch ( Exception e )
            {
                targetRulesBinder.addError( "Impossible to include programmatic rules from class '%s': %s", className,
                                            e.getMessage() );
            }
        }
    }

    private void install( RulesModule rulesModule )
    {
        // that's an hack, shall not be taken in consideration!!! :)
        rulesModule.configure( new PrefixedRulesBinder( targetRulesBinder,
                                                        memoryRulesBinder.getPatternStack().toString() ) );
    }

}