/*
* Copyright 2011 JBoss Inc
*
* 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 org.drools.compiler.compiler;
import java.util.Collections;
import java.util.List;
import org.antlr.runtime.ANTLRStringStream;
import org.antlr.runtime.CommonTokenStream;
import org.antlr.runtime.RecognitionException;
import org.antlr.runtime.RecognizerSharedState;
import org.drools.compiler.lang.DRLExpressions;
import org.drools.compiler.lang.DRLLexer;
import org.drools.compiler.lang.ParserHelper;
import org.drools.compiler.lang.descr.BaseDescr;
import org.drools.compiler.lang.descr.ConstraintConnectiveDescr;
import org.kie.internal.builder.conf.LanguageLevelOption;
/**
* This is a helper class that provides helper methods to parse expressions
* using both the DRLExpressions parser and the DRLExprTree parser.
*/
public class DrlExprParser {
private ParserHelper helper = null;
private final LanguageLevelOption languageLevel;
public DrlExprParser(LanguageLevelOption languageLevel) {
this.languageLevel = languageLevel;
}
/** Parse an expression from text */
public ConstraintConnectiveDescr parse( final String text ) {
ConstraintConnectiveDescr constraint = null;
try {
DRLLexer lexer = DRLFactory.getDRLLexer(new ANTLRStringStream(text), languageLevel);
CommonTokenStream input = new CommonTokenStream( lexer );
RecognizerSharedState state = new RecognizerSharedState();
helper = new ParserHelper( input, state, languageLevel );
DRLExpressions parser = DRLFactory.getDRLExpressions(input, state, helper, languageLevel);
parser.setBuildDescr( true );
parser.setLeftMostExpr( null ); // setting initial value just in case
BaseDescr expr = parser.conditionalOrExpression();
if ( expr != null && !parser.hasErrors() ) {
constraint = ConstraintConnectiveDescr.newAnd();
constraint.addOrMerge( expr );
}
} catch ( RecognitionException e ) {
helper.reportError( e );
}
return constraint;
}
public String getLeftMostExpr() {
return helper != null ? helper.getLeftMostExpr() : null;
}
/**
* @return true if there were parser errors.
*/
public boolean hasErrors() {
return helper != null && helper.hasErrors();
}
/**
* @return a list of errors found while parsing.
*/
@SuppressWarnings("unchecked")
public List<DroolsParserException> getErrors() {
return helper != null ? helper.getErrors() : Collections.EMPTY_LIST;
}
}