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/*
 * 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.
 */
package org.apache.lucene.analysis.charfilter;


import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.lucene.analysis.util.CharFilterFactory;
import org.apache.lucene.analysis.util.ResourceLoader;
import org.apache.lucene.analysis.util.ResourceLoaderAware;

/**
 * Factory for {@link MappingCharFilter}. 
 *  * <fieldType name="text_map" class="solr.TextField" positionIncrementGap="100">
 *   <analyzer>
 *     <charFilter class="solr.MappingCharFilterFactory" mapping="mapping.txt"/>
 *     <tokenizer class="solr.WhitespaceTokenizerFactory"/>
 *   </analyzer>
 * </fieldType>
 *
 * @since Solr 1.4
 * @lucene.spi {@value #NAME}
 */
public class MappingCharFilterFactory extends CharFilterFactory implements
    ResourceLoaderAware {

  /** SPI name */
  public static final String NAME = "mapping";

  protected NormalizeCharMap normMap;
  private final String mapping;

  /** Creates a new MappingCharFilterFactory */
  public MappingCharFilterFactory(Map args) {
    super(args);
    mapping = get(args, "mapping");
    if (!args.isEmpty()) {
      throw new IllegalArgumentException("Unknown parameters: " + args);
    }
  }

  @Override
  public void inform(ResourceLoader loader) throws IOException {
    if (mapping != null) {
      List wlist = null;
      List files = splitFileNames(mapping);
      wlist = new ArrayList<>();
      for (String file : files) {
        List lines = getLines(loader, file.trim());
        wlist.addAll(lines);
      }
      final NormalizeCharMap.Builder builder = new NormalizeCharMap.Builder();
      parseRules(wlist, builder);
      normMap = builder.build();
      if (normMap.map == null) {
        // if the inner FST is null, it means it accepts nothing (e.g. the file is empty)
        // so just set the whole map to null
        normMap = null;
      }
    }
  }

  @Override
  public Reader create(Reader input) {
    // if the map is null, it means there's actually no mappings... just return the original stream
    // as there is nothing to do here.
    return normMap == null ? input : new MappingCharFilter(normMap,input);
  }

  @Override
  public Reader normalize(Reader input) {
    return create(input);
  }

  // "source" => "target"
  static Pattern p = Pattern.compile( "\"(.*)\"\\s*=>\\s*\"(.*)\"\\s*$" );

  protected void parseRules( List rules, NormalizeCharMap.Builder builder ){
    for( String rule : rules ){
      Matcher m = p.matcher( rule );
      if( !m.find() )
        throw new IllegalArgumentException("Invalid Mapping Rule : [" + rule + "], file = " + mapping);
      builder.add( parseString( m.group( 1 ) ), parseString( m.group( 2 ) ) );
    }
  }

  char[] out = new char[256];
  
  protected String parseString( String s ){
    int readPos = 0;
    int len = s.length();
    int writePos = 0;
    while( readPos < len ){
      char c = s.charAt( readPos++ );
      if( c == '\\' ){
        if( readPos >= len )
          throw new IllegalArgumentException("Invalid escaped char in [" + s + "]");
        c = s.charAt( readPos++ );
        switch( c ) {
          case '\\' : c = '\\'; break;
          case '"' : c = '"'; break;
          case 'n' : c = '\n'; break;
          case 't' : c = '\t'; break;
          case 'r' : c = '\r'; break;
          case 'b' : c = '\b'; break;
          case 'f' : c = '\f'; break;
          case 'u' :
            if( readPos + 3 >= len )
              throw new IllegalArgumentException("Invalid escaped char in [" + s + "]");
            c = (char)Integer.parseInt( s.substring( readPos, readPos + 4 ), 16 );
            readPos += 4;
            break;
        }
      }
      out[writePos++] = c;
    }
    return new String( out, 0, writePos );
  }

}