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/*
 * Copyright 2006 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.lang.dsl;

import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import org.drools.compiler.ParserError;
import org.mvel2.util.ParseTools;

/**
 * An ANTLR-driven implementation for the DSL Mapping Entry interface
 */
public class AntlrDSLMappingEntry extends AbstractDSLMappingEntry {

    public AntlrDSLMappingEntry() {
        this( DSLMappingEntry.ANY,
                DSLMappingEntry.EMPTY_METADATA,
                null,
                null,
                null,
                null );
    }

    public AntlrDSLMappingEntry(final Section section,
            final MetaData metadata,
            final String key,
            final String value,
            final String keyPattern,
            final String valuePattern) {
        setSection( section );
        setMetaData( metadata );
        setMappingKey( key );
        setMappingValue( value );
        setKeyPattern( keyPattern );
        setValuePattern( valuePattern );
    }

    /**
     * @param KEY
     *            the key to set
     */
    public void setKeyPattern(final String keyPat) {
        //the "key" in this case is already mostly formed into 
        //a pattern by ANTLR, and just requires a bit of post-processing.

        if ( keyPat != null ) {
            String trimmed = keyPat.trim();
            // escaping the special character $
            String keyPattern = trimmed.replaceAll( "\\$", "\\\\\\$" );
            // unescaping the special character #
            keyPattern = keyPattern.replaceAll( "\\\\#", "#" );

            if ( !keyPattern.startsWith( "^" ) ) {
                // making it start after a non word char or at line start
                // JDK 5 (java version 1.5.0_22) is buggy: doesn't handle alternatives within
                // zero-width lookbehind assertions. As a workaround, we use an alternative of
                // zero-width lookbehind assertions, slightly longer, but simpler than anything else.
                // keyPattern = "(?<=\\W|^)" + keyPattern; // works in JDK >=6
                keyPattern = "(?:(?<=^)|(?<=\\W))" + keyPattern;
            }

            // If the pattern ends with a pure variable whose pattern could create
            // a greedy match, append a line end to avoid multiple line matching
            if ( keyPattern.endsWith( "(.*?)" ) ) {
                keyPattern += "$";
            } else {
                keyPattern += "(?=\\W|$)";
            }

            // fix variables offset
            fixVariableOffsets();

            // setting the key pattern and making it space insensitive
            //first, look to see if it's 
            if ( trimmed.startsWith( "-" ) && (!trimmed.startsWith( "-\\s*" )) ) {
                int index = keyPattern.indexOf( '-' ) + 1;
                keyPattern = keyPattern.substring( 0, index ) + "\\s*" + keyPattern.substring( index ).trim();
            }

            // Make the pattern space insensitive. 
            keyPattern = keyPattern.replaceAll( "\\s+", "\\\\s+" );
            // normalize duplications
            keyPattern = keyPattern.replaceAll( "(\\\\s\\+)+", "\\\\s+" );

            setKeyPattern( Pattern.compile( keyPattern, Pattern.DOTALL | Pattern.MULTILINE ) );

        } else {
            setKeyPattern( (Pattern) null );
        }
    }

    private void fixVariableOffsets() {
        char[] input = getMappingKey().toCharArray();
        int counter = 1;
        boolean insideCurly = false;
        for ( int i = 0; i < input.length; i++ ) {
            switch ( input[i] ) {
            case '\\' :
                // next char is escaped
                i++;
                break;
            case '(' :
                // Don't count /.{x(y}./ or /.(?./
                if( ! insideCurly &&
                        (i == input.length - 1 || input[i+1] != '?' ) ) counter++;
                break;
            case '{' :
                if ( insideCurly ) {
                    i = ParseTools.balancedCapture( input,
                            i,
                    '{' );
                } else {
                    insideCurly = true;
                    updateVariableIndex( i,
                            counter );
                    counter++;
                }
                break;
            case '}' :
                if ( insideCurly ) insideCurly = false;
            }
        }
    }

    private void updateVariableIndex(int offset,
            int counter) {
        String subs = getMappingKey().substring( offset );
        for ( Map.Entry entry : getVariables().entrySet() ) {
            if ( subs.startsWith( "{" + entry.getKey() ) && ((subs.charAt( entry.getKey().length() + 1 ) == '}') || (subs.charAt( entry.getKey().length() + 1 ) == ':')) ) {
                entry.setValue( Integer.valueOf( counter ) );
                break;
            }
        }
    }

    /**
     * @param value
     *            the value to set
     */
    public void setValuePattern(String value) {
        if ( value != null ) {
            StringBuilder valuePatternBuffer = new StringBuilder();

            valuePatternBuffer.append( value );
            if ( value.endsWith( " " ) ) {
                valuePatternBuffer.deleteCharAt( valuePatternBuffer.length() - 1 );
            }

            // unescaping the special character # and creating the line breaks
            String pat = valuePatternBuffer.toString().replaceAll( "\\\\(#|\\{|\\})", "$1" ).
            replaceAll( "\\\\n", "\n" ).
            replaceAll( "\\\\\\$", "\\$" );

            super.setValuePattern( pat );
        }

    }
}