    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.text.translate;
    018
    019import java.io.IOException;
    020import java.io.Writer;
    021import java.security.InvalidParameterException;
    022import java.util.BitSet;
    023import java.util.HashMap;
    024import java.util.Map;
    025
    026/**
    027 * Translates a value using a lookup table.
    028 *
    029 * @since 1.0
    030 */
    031public class LookupTranslator extends CharSequenceTranslator {
    032
    033    /** The mapping to be used in translation. */
    034    private final Map<String, String> lookupMap;
    035
    036    /** The first character of each key in the lookupMap. */
    037    private final BitSet prefixSet;
    038
    039    /** The length of the shortest key in the lookupMap. */
    040    private final int shortest;
    041
    042    /** The length of the longest key in the lookupMap. */
    043    private final int longest;
    044
    045    /**
    046     * Constructs the lookup table to be used in translation
    047     *
    048     * Note that, as of Lang 3.1 (the origin of this code), the key to the lookup
    049     * table is converted to a java.lang.String. This is because we need the key
    050     * to support hashCode and equals(Object), allowing it to be the key for a
    051     * HashMap. See LANG-882.
    052     *
    053     * @param lookupMap Map&lt;CharSequence, CharSequence&gt; table of translator
    054     *                  mappings
    055     */
    056    public LookupTranslator(final Map<CharSequence, CharSequence> lookupMap) {
    057        if (lookupMap == null) {
    058            throw new InvalidParameterException("lookupMap cannot be null");
    059        }
    060        this.lookupMap = new HashMap<>();
    061        this.prefixSet = new BitSet();
    062        int currentShortest = Integer.MAX_VALUE;
    063        int currentLongest = 0;
    064
    065        for (final Map.Entry<CharSequence, CharSequence> pair : lookupMap.entrySet()) {
    066            this.lookupMap.put(pair.getKey().toString(), pair.getValue().toString());
    067            this.prefixSet.set(pair.getKey().charAt(0));
    068            final int sz = pair.getKey().length();
    069            if (sz < currentShortest) {
    070                currentShortest = sz;
    071            }
    072            if (sz > currentLongest) {
    073                currentLongest = sz;
    074            }
    075        }
    076        this.shortest = currentShortest;
    077        this.longest = currentLongest;
    078    }
    079
    080    /**
    081     * {@inheritDoc}
    082     */
    083    @Override
    084    public int translate(final CharSequence input, final int index, final Writer writer) throws IOException {
    085        // check if translation exists for the input at position index
    086        if (prefixSet.get(input.charAt(index))) {
    087            int max = longest;
    088            if (index + longest > input.length()) {
    089                max = input.length() - index;
    090            }
    091            // implement greedy algorithm by trying maximum match first
    092            for (int i = max; i >= shortest; i--) {
    093                final CharSequence subSeq = input.subSequence(index, index + i);
    094                final String result = lookupMap.get(subSeq.toString());
    095
    096                if (result != null) {
    097                    writer.write(result);
    098                    return Character.codePointCount(subSeq, 0, subSeq.length());
    099                }
    100            }
    101        }
    102        return 0;
    103    }
    104}