    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 */
    017
    018package org.apache.commons.codec.language.bm;
    019
    020import java.io.InputStream;
    021import java.util.ArrayList;
    022import java.util.Arrays;
    023import java.util.Collections;
    024import java.util.Comparator;
    025import java.util.EnumMap;
    026import java.util.HashMap;
    027import java.util.HashSet;
    028import java.util.List;
    029import java.util.Map;
    030import java.util.Scanner;
    031import java.util.Set;
    032import java.util.regex.Matcher;
    033import java.util.regex.Pattern;
    034
    035import org.apache.commons.codec.language.bm.Languages.LanguageSet;
    036
    037/**
    038 * A phoneme rule.
    039 * <p>
    040 * Rules have a pattern, left context, right context, output phoneme, set of languages for which they apply
    041 * and a logical flag indicating if all languages must be in play. A rule matches if:
    042 * <ul>
    043 * <li>the pattern matches at the current position</li>
    044 * <li>the string up until the beginning of the pattern matches the left context</li>
    045 * <li>the string from the end of the pattern matches the right context</li>
    046 * <li>logical is ALL and all languages are in scope; or</li>
    047 * <li>logical is any other value and at least one language is in scope</li>
    048 * </ul>
    049 * <p>
    050 * Rules are typically generated by parsing rules resources. In normal use, there will be no need for the user
    051 * to explicitly construct their own.
    052 * <p>
    053 * Rules are immutable and thread-safe.
    054 * <p>
    055 * <b>Rules resources</b>
    056 * <p>
    057 * Rules are typically loaded from resource files. These are UTF-8 encoded text files. They are systematically
    058 * named following the pattern:
    059 * <blockquote>org/apache/commons/codec/language/bm/${NameType#getName}_${RuleType#getName}_${language}.txt</blockquote>
    060 * <p>
    061 * The format of these resources is the following:
    062 * <ul>
    063 * <li><b>Rules:</b> whitespace separated, double-quoted strings. There should be 4 columns to each row, and these
    064 * will be interpreted as:
    065 * <ol>
    066 * <li>pattern</li>
    067 * <li>left context</li>
    068 * <li>right context</li>
    069 * <li>phoneme</li>
    070 * </ol>
    071 * </li>
    072 * <li><b>End-of-line comments:</b> Any occurrence of '//' will cause all text following on that line to be discarded
    073 * as a comment.</li>
    074 * <li><b>Multi-line comments:</b> Any line starting with '/*' will start multi-line commenting mode. This will skip
    075 * all content until a line ending in '*' and '/' is found.</li>
    076 * <li><b>Blank lines:</b> All blank lines will be skipped.</li>
    077 * </ul>
    078 *
    079 * @since 1.6
    080 * @version $Id$
    081 */
    082public class Rule {
    083
    084    public static final class Phoneme implements PhonemeExpr {
    085        public static final Comparator<Phoneme> COMPARATOR = new Comparator<Phoneme>() {
    086            @Override
    087            public int compare(final Phoneme o1, final Phoneme o2) {
    088                for (int i = 0; i < o1.phonemeText.length(); i++) {
    089                    if (i >= o2.phonemeText.length()) {
    090                        return +1;
    091                    }
    092                    final int c = o1.phonemeText.charAt(i) - o2.phonemeText.charAt(i);
    093                    if (c != 0) {
    094                        return c;
    095                    }
    096                }
    097
    098                if (o1.phonemeText.length() < o2.phonemeText.length()) {
    099                    return -1;
    100                }
    101
    102                return 0;
    103            }
    104        };
    105
    106        private final StringBuilder phonemeText;
    107        private final Languages.LanguageSet languages;
    108
    109        public Phoneme(final CharSequence phonemeText, final Languages.LanguageSet languages) {
    110            this.phonemeText = new StringBuilder(phonemeText);
    111            this.languages = languages;
    112        }
    113
    114        public Phoneme(final Phoneme phonemeLeft, final Phoneme phonemeRight) {
    115            this(phonemeLeft.phonemeText, phonemeLeft.languages);
    116            this.phonemeText.append(phonemeRight.phonemeText);
    117        }
    118
    119        public Phoneme(final Phoneme phonemeLeft, final Phoneme phonemeRight, final Languages.LanguageSet languages) {
    120            this(phonemeLeft.phonemeText, languages);
    121            this.phonemeText.append(phonemeRight.phonemeText);
    122        }
    123
    124        public Phoneme append(final CharSequence str) {
    125            this.phonemeText.append(str);
    126            return this;
    127        }
    128
    129        public Languages.LanguageSet getLanguages() {
    130            return this.languages;
    131        }
    132
    133        @Override
    134        public Iterable<Phoneme> getPhonemes() {
    135            return Collections.singleton(this);
    136        }
    137
    138        public CharSequence getPhonemeText() {
    139            return this.phonemeText;
    140        }
    141
    142        /**
    143         * Deprecated since 1.9.
    144         *
    145         * @param right the Phoneme to join
    146         * @return a new Phoneme
    147         * @deprecated since 1.9
    148         */
    149        @Deprecated
    150        public Phoneme join(final Phoneme right) {
    151            return new Phoneme(this.phonemeText.toString() + right.phonemeText.toString(),
    152                               this.languages.restrictTo(right.languages));
    153        }
    154
    155        /**
    156         * Returns a new Phoneme with the same text but a union of its
    157         * current language set and the given one.
    158         *
    159         * @param lang the language set to merge
    160         * @return a new Phoneme
    161         */
    162        public Phoneme mergeWithLanguage(final LanguageSet lang) {
    163          return new Phoneme(this.phonemeText.toString(), this.languages.merge(lang));
    164        }
    165
    166        @Override
    167        public String toString() {
    168          return phonemeText.toString() + "[" + languages + "]";
    169        }
    170    }
    171
    172    public interface PhonemeExpr {
    173        Iterable<Phoneme> getPhonemes();
    174    }
    175
    176    public static final class PhonemeList implements PhonemeExpr {
    177        private final List<Phoneme> phonemes;
    178
    179        public PhonemeList(final List<Phoneme> phonemes) {
    180            this.phonemes = phonemes;
    181        }
    182
    183        @Override
    184        public List<Phoneme> getPhonemes() {
    185            return this.phonemes;
    186        }
    187    }
    188
    189    /**
    190     * A minimal wrapper around the functionality of Pattern that we use, to allow for alternate implementations.
    191     */
    192    public interface RPattern {
    193        boolean isMatch(CharSequence input);
    194    }
    195
    196    public static final RPattern ALL_STRINGS_RMATCHER = new RPattern() {
    197        @Override
    198        public boolean isMatch(final CharSequence input) {
    199            return true;
    200        }
    201    };
    202
    203    public static final String ALL = "ALL";
    204
    205    private static final String DOUBLE_QUOTE = "\"";
    206
    207    private static final String HASH_INCLUDE = "#include";
    208
    209    private static final Map<NameType, Map<RuleType, Map<String, Map<String, List<Rule>>>>> RULES =
    210            new EnumMap<>(NameType.class);
    211
    212    static {
    213        for (final NameType s : NameType.values()) {
    214            final Map<RuleType, Map<String, Map<String, List<Rule>>>> rts =
    215                    new EnumMap<>(RuleType.class);
    216
    217            for (final RuleType rt : RuleType.values()) {
    218                final Map<String, Map<String, List<Rule>>> rs = new HashMap<>();
    219
    220                final Languages ls = Languages.getInstance(s);
    221                for (final String l : ls.getLanguages()) {
    222                    try (final Scanner scanner = createScanner(s, rt, l)) {
    223                        rs.put(l, parseRules(scanner, createResourceName(s, rt, l)));
    224                    } catch (final IllegalStateException e) {
    225                        throw new IllegalStateException("Problem processing " + createResourceName(s, rt, l), e);
    226                    }
    227                }
    228                if (!rt.equals(RuleType.RULES)) {
    229                    try (final Scanner scanner = createScanner(s, rt, "common")) {
    230                        rs.put("common", parseRules(scanner, createResourceName(s, rt, "common")));
    231                    }
    232                }
    233
    234                rts.put(rt, Collections.unmodifiableMap(rs));
    235            }
    236
    237            RULES.put(s, Collections.unmodifiableMap(rts));
    238        }
    239    }
    240
    241    private static boolean contains(final CharSequence chars, final char input) {
    242        for (int i = 0; i < chars.length(); i++) {
    243            if (chars.charAt(i) == input) {
    244                return true;
    245            }
    246        }
    247        return false;
    248    }
    249
    250    private static String createResourceName(final NameType nameType, final RuleType rt, final String lang) {
    251        return String.format("org/apache/commons/codec/language/bm/%s_%s_%s.txt",
    252                             nameType.getName(), rt.getName(), lang);
    253    }
    254
    255    private static Scanner createScanner(final NameType nameType, final RuleType rt, final String lang) {
    256        final String resName = createResourceName(nameType, rt, lang);
    257        final InputStream rulesIS = Languages.class.getClassLoader().getResourceAsStream(resName);
    258
    259        if (rulesIS == null) {
    260            throw new IllegalArgumentException("Unable to load resource: " + resName);
    261        }
    262
    263        return new Scanner(rulesIS, ResourceConstants.ENCODING);
    264    }
    265
    266    private static Scanner createScanner(final String lang) {
    267        final String resName = String.format("org/apache/commons/codec/language/bm/%s.txt", lang);
    268        final InputStream rulesIS = Languages.class.getClassLoader().getResourceAsStream(resName);
    269
    270        if (rulesIS == null) {
    271            throw new IllegalArgumentException("Unable to load resource: " + resName);
    272        }
    273
    274        return new Scanner(rulesIS, ResourceConstants.ENCODING);
    275    }
    276
    277    private static boolean endsWith(final CharSequence input, final CharSequence suffix) {
    278        if (suffix.length() > input.length()) {
    279            return false;
    280        }
    281        for (int i = input.length() - 1, j = suffix.length() - 1; j >= 0; i--, j--) {
    282            if (input.charAt(i) != suffix.charAt(j)) {
    283                return false;
    284            }
    285        }
    286        return true;
    287    }
    288
    289    /**
    290     * Gets rules for a combination of name type, rule type and languages.
    291     *
    292     * @param nameType
    293     *            the NameType to consider
    294     * @param rt
    295     *            the RuleType to consider
    296     * @param langs
    297     *            the set of languages to consider
    298     * @return a list of Rules that apply
    299     */
    300    public static List<Rule> getInstance(final NameType nameType, final RuleType rt,
    301                                         final Languages.LanguageSet langs) {
    302        final Map<String, List<Rule>> ruleMap = getInstanceMap(nameType, rt, langs);
    303        final List<Rule> allRules = new ArrayList<>();
    304        for (final List<Rule> rules : ruleMap.values()) {
    305            allRules.addAll(rules);
    306        }
    307        return allRules;
    308    }
    309
    310    /**
    311     * Gets rules for a combination of name type, rule type and a single language.
    312     *
    313     * @param nameType
    314     *            the NameType to consider
    315     * @param rt
    316     *            the RuleType to consider
    317     * @param lang
    318     *            the language to consider
    319     * @return a list of Rules that apply
    320     */
    321    public static List<Rule> getInstance(final NameType nameType, final RuleType rt, final String lang) {
    322        return getInstance(nameType, rt, LanguageSet.from(new HashSet<>(Arrays.asList(lang))));
    323    }
    324
    325    /**
    326     * Gets rules for a combination of name type, rule type and languages.
    327     *
    328     * @param nameType
    329     *            the NameType to consider
    330     * @param rt
    331     *            the RuleType to consider
    332     * @param langs
    333     *            the set of languages to consider
    334     * @return a map containing all Rules that apply, grouped by the first character of the rule pattern
    335     * @since 1.9
    336     */
    337    public static Map<String, List<Rule>> getInstanceMap(final NameType nameType, final RuleType rt,
    338                                                         final Languages.LanguageSet langs) {
    339        return langs.isSingleton() ? getInstanceMap(nameType, rt, langs.getAny()) :
    340                                     getInstanceMap(nameType, rt, Languages.ANY);
    341    }
    342
    343    /**
    344     * Gets rules for a combination of name type, rule type and a single language.
    345     *
    346     * @param nameType
    347     *            the NameType to consider
    348     * @param rt
    349     *            the RuleType to consider
    350     * @param lang
    351     *            the language to consider
    352     * @return a map containing all Rules that apply, grouped by the first character of the rule pattern
    353     * @since 1.9
    354     */
    355    public static Map<String, List<Rule>> getInstanceMap(final NameType nameType, final RuleType rt,
    356                                                         final String lang) {
    357        final Map<String, List<Rule>> rules = RULES.get(nameType).get(rt).get(lang);
    358
    359        if (rules == null) {
    360            throw new IllegalArgumentException(String.format("No rules found for %s, %s, %s.",
    361                                               nameType.getName(), rt.getName(), lang));
    362        }
    363
    364        return rules;
    365    }
    366
    367    private static Phoneme parsePhoneme(final String ph) {
    368        final int open = ph.indexOf("[");
    369        if (open >= 0) {
    370            if (!ph.endsWith("]")) {
    371                throw new IllegalArgumentException("Phoneme expression contains a '[' but does not end in ']'");
    372            }
    373            final String before = ph.substring(0, open);
    374            final String in = ph.substring(open + 1, ph.length() - 1);
    375            final Set<String> langs = new HashSet<>(Arrays.asList(in.split("[+]")));
    376
    377            return new Phoneme(before, Languages.LanguageSet.from(langs));
    378        }
    379        return new Phoneme(ph, Languages.ANY_LANGUAGE);
    380    }
    381
    382    private static PhonemeExpr parsePhonemeExpr(final String ph) {
    383        if (ph.startsWith("(")) { // we have a bracketed list of options
    384            if (!ph.endsWith(")")) {
    385                throw new IllegalArgumentException("Phoneme starts with '(' so must end with ')'");
    386            }
    387
    388            final List<Phoneme> phs = new ArrayList<>();
    389            final String body = ph.substring(1, ph.length() - 1);
    390            for (final String part : body.split("[|]")) {
    391                phs.add(parsePhoneme(part));
    392            }
    393            if (body.startsWith("|") || body.endsWith("|")) {
    394                phs.add(new Phoneme("", Languages.ANY_LANGUAGE));
    395            }
    396
    397            return new PhonemeList(phs);
    398        }
    399        return parsePhoneme(ph);
    400    }
    401
    402    private static Map<String, List<Rule>> parseRules(final Scanner scanner, final String location) {
    403        final Map<String, List<Rule>> lines = new HashMap<>();
    404        int currentLine = 0;
    405
    406        boolean inMultilineComment = false;
    407        while (scanner.hasNextLine()) {
    408            currentLine++;
    409            final String rawLine = scanner.nextLine();
    410            String line = rawLine;
    411
    412            if (inMultilineComment) {
    413                if (line.endsWith(ResourceConstants.EXT_CMT_END)) {
    414                    inMultilineComment = false;
    415                }
    416            } else {
    417                if (line.startsWith(ResourceConstants.EXT_CMT_START)) {
    418                    inMultilineComment = true;
    419                } else {
    420                    // discard comments
    421                    final int cmtI = line.indexOf(ResourceConstants.CMT);
    422                    if (cmtI >= 0) {
    423                        line = line.substring(0, cmtI);
    424                    }
    425
    426                    // trim leading-trailing whitespace
    427                    line = line.trim();
    428
    429                    if (line.length() == 0) {
    430                        continue; // empty lines can be safely skipped
    431                    }
    432
    433                    if (line.startsWith(HASH_INCLUDE)) {
    434                        // include statement
    435                        final String incl = line.substring(HASH_INCLUDE.length()).trim();
    436                        if (incl.contains(" ")) {
    437                            throw new IllegalArgumentException("Malformed import statement '" + rawLine + "' in " +
    438                                                               location);
    439                        }
    440                        try (final Scanner hashIncludeScanner = createScanner(incl)) {
    441                            lines.putAll(parseRules(hashIncludeScanner, location + "->" + incl));
    442                        }
    443                    } else {
    444                        // rule
    445                        final String[] parts = line.split("\\s+");
    446                        if (parts.length != 4) {
    447                            throw new IllegalArgumentException("Malformed rule statement split into " + parts.length +
    448                                                               " parts: " + rawLine + " in " + location);
    449                        }
    450                        try {
    451                            final String pat = stripQuotes(parts[0]);
    452                            final String lCon = stripQuotes(parts[1]);
    453                            final String rCon = stripQuotes(parts[2]);
    454                            final PhonemeExpr ph = parsePhonemeExpr(stripQuotes(parts[3]));
    455                            final int cLine = currentLine;
    456                            final Rule r = new Rule(pat, lCon, rCon, ph) {
    457                                private final int myLine = cLine;
    458                                private final String loc = location;
    459
    460                                @Override
    461                                public String toString() {
    462                                    final StringBuilder sb = new StringBuilder();
    463                                    sb.append("Rule");
    464                                    sb.append("{line=").append(myLine);
    465                                    sb.append(", loc='").append(loc).append('\'');
    466                                    sb.append(", pat='").append(pat).append('\'');
    467                                    sb.append(", lcon='").append(lCon).append('\'');
    468                                    sb.append(", rcon='").append(rCon).append('\'');
    469                                    sb.append('}');
    470                                    return sb.toString();
    471                                }
    472                            };
    473                            final String patternKey = r.pattern.substring(0,1);
    474                            List<Rule> rules = lines.get(patternKey);
    475                            if (rules == null) {
    476                                rules = new ArrayList<>();
    477                                lines.put(patternKey, rules);
    478                            }
    479                            rules.add(r);
    480                        } catch (final IllegalArgumentException e) {
    481                            throw new IllegalStateException("Problem parsing line '" + currentLine + "' in " +
    482                                                            location, e);
    483                        }
    484                    }
    485                }
    486            }
    487        }
    488
    489        return lines;
    490    }
    491
    492    /**
    493     * Attempts to compile the regex into direct string ops, falling back to Pattern and Matcher in the worst case.
    494     *
    495     * @param regex
    496     *            the regular expression to compile
    497     * @return an RPattern that will match this regex
    498     */
    499    private static RPattern pattern(final String regex) {
    500        final boolean startsWith = regex.startsWith("^");
    501        final boolean endsWith = regex.endsWith("$");
    502        final String content = regex.substring(startsWith ? 1 : 0, endsWith ? regex.length() - 1 : regex.length());
    503        final boolean boxes = content.contains("[");
    504
    505        if (!boxes) {
    506            if (startsWith && endsWith) {
    507                // exact match
    508                if (content.length() == 0) {
    509                    // empty
    510                    return new RPattern() {
    511                        @Override
    512                        public boolean isMatch(final CharSequence input) {
    513                            return input.length() == 0;
    514                        }
    515                    };
    516                }
    517                return new RPattern() {
    518                    @Override
    519                    public boolean isMatch(final CharSequence input) {
    520                        return input.equals(content);
    521                    }
    522                };
    523            } else if ((startsWith || endsWith) && content.length() == 0) {
    524                // matches every string
    525                return ALL_STRINGS_RMATCHER;
    526            } else if (startsWith) {
    527                // matches from start
    528                return new RPattern() {
    529                    @Override
    530                    public boolean isMatch(final CharSequence input) {
    531                        return startsWith(input, content);
    532                    }
    533                };
    534            } else if (endsWith) {
    535                // matches from start
    536                return new RPattern() {
    537                    @Override
    538                    public boolean isMatch(final CharSequence input) {
    539                        return endsWith(input, content);
    540                    }
    541                };
    542            }
    543        } else {
    544            final boolean startsWithBox = content.startsWith("[");
    545            final boolean endsWithBox = content.endsWith("]");
    546
    547            if (startsWithBox && endsWithBox) {
    548                String boxContent = content.substring(1, content.length() - 1);
    549                if (!boxContent.contains("[")) {
    550                    // box containing alternatives
    551                    final boolean negate = boxContent.startsWith("^");
    552                    if (negate) {
    553                        boxContent = boxContent.substring(1);
    554                    }
    555                    final String bContent = boxContent;
    556                    final boolean shouldMatch = !negate;
    557
    558                    if (startsWith && endsWith) {
    559                        // exact match
    560                        return new RPattern() {
    561                            @Override
    562                            public boolean isMatch(final CharSequence input) {
    563                                return input.length() == 1 && contains(bContent, input.charAt(0)) == shouldMatch;
    564                            }
    565                        };
    566                    } else if (startsWith) {
    567                        // first char
    568                        return new RPattern() {
    569                            @Override
    570                            public boolean isMatch(final CharSequence input) {
    571                                return input.length() > 0 && contains(bContent, input.charAt(0)) == shouldMatch;
    572                            }
    573                        };
    574                    } else if (endsWith) {
    575                        // last char
    576                        return new RPattern() {
    577                            @Override
    578                            public boolean isMatch(final CharSequence input) {
    579                                return input.length() > 0 &&
    580                                       contains(bContent, input.charAt(input.length() - 1)) == shouldMatch;
    581                            }
    582                        };
    583                    }
    584                }
    585            }
    586        }
    587
    588        return new RPattern() {
    589            Pattern pattern = Pattern.compile(regex);
    590
    591            @Override
    592            public boolean isMatch(final CharSequence input) {
    593                final Matcher matcher = pattern.matcher(input);
    594                return matcher.find();
    595            }
    596        };
    597    }
    598
    599    private static boolean startsWith(final CharSequence input, final CharSequence prefix) {
    600        if (prefix.length() > input.length()) {
    601            return false;
    602        }
    603        for (int i = 0; i < prefix.length(); i++) {
    604            if (input.charAt(i) != prefix.charAt(i)) {
    605                return false;
    606            }
    607        }
    608        return true;
    609    }
    610
    611    private static String stripQuotes(String str) {
    612        if (str.startsWith(DOUBLE_QUOTE)) {
    613            str = str.substring(1);
    614        }
    615
    616        if (str.endsWith(DOUBLE_QUOTE)) {
    617            str = str.substring(0, str.length() - 1);
    618        }
    619
    620        return str;
    621    }
    622
    623    private final RPattern lContext;
    624
    625    private final String pattern;
    626
    627    private final PhonemeExpr phoneme;
    628
    629    private final RPattern rContext;
    630
    631    /**
    632     * Creates a new rule.
    633     *
    634     * @param pattern
    635     *            the pattern
    636     * @param lContext
    637     *            the left context
    638     * @param rContext
    639     *            the right context
    640     * @param phoneme
    641     *            the resulting phoneme
    642     */
    643    public Rule(final String pattern, final String lContext, final String rContext, final PhonemeExpr phoneme) {
    644        this.pattern = pattern;
    645        this.lContext = pattern(lContext + "$");
    646        this.rContext = pattern("^" + rContext);
    647        this.phoneme = phoneme;
    648    }
    649
    650    /**
    651     * Gets the left context. This is a regular expression that must match to the left of the pattern.
    652     *
    653     * @return the left context Pattern
    654     */
    655    public RPattern getLContext() {
    656        return this.lContext;
    657    }
    658
    659    /**
    660     * Gets the pattern. This is a string-literal that must exactly match.
    661     *
    662     * @return the pattern
    663     */
    664    public String getPattern() {
    665        return this.pattern;
    666    }
    667
    668    /**
    669     * Gets the phoneme. If the rule matches, this is the phoneme associated with the pattern match.
    670     *
    671     * @return the phoneme
    672     */
    673    public PhonemeExpr getPhoneme() {
    674        return this.phoneme;
    675    }
    676
    677    /**
    678     * Gets the right context. This is a regular expression that must match to the right of the pattern.
    679     *
    680     * @return the right context Pattern
    681     */
    682    public RPattern getRContext() {
    683        return this.rContext;
    684    }
    685
    686    /**
    687     * Decides if the pattern and context match the input starting at a position. It is a match if the
    688     * <code>lContext</code> matches <code>input</code> up to <code>i</code>, <code>pattern</code> matches at i and
    689     * <code>rContext</code> matches from the end of the match of <code>pattern</code> to the end of <code>input</code>.
    690     *
    691     * @param input
    692     *            the input String
    693     * @param i
    694     *            the int position within the input
    695     * @return true if the pattern and left/right context match, false otherwise
    696     */
    697    public boolean patternAndContextMatches(final CharSequence input, final int i) {
    698        if (i < 0) {
    699            throw new IndexOutOfBoundsException("Can not match pattern at negative indexes");
    700        }
    701
    702        final int patternLength = this.pattern.length();
    703        final int ipl = i + patternLength;
    704
    705        if (ipl > input.length()) {
    706            // not enough room for the pattern to match
    707            return false;
    708        }
    709
    710        // evaluate the pattern, left context and right context
    711        // fail early if any of the evaluations is not successful
    712        if (!input.subSequence(i, ipl).equals(this.pattern)) {
    713            return false;
    714        } else if (!this.rContext.isMatch(input.subSequence(ipl, input.length()))) {
    715            return false;
    716        }
    717        return this.lContext.isMatch(input.subSequence(0, i));
    718    }
    719}