/*
    * 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.commons.codec.language.bm;
  
  import java.io.InputStream;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.EnumMap;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Scanner;
  import java.util.Set;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  /**
   * A phoneme rule.
   * <p>
   * Rules have a pattern, left context, right context, output phoneme, set of languages for which they apply
   * and a logical flag indicating if all languages must be in play. A rule matches if:
   * <ul>
   * <li>the pattern matches at the current position</li>
   * <li>the string up until the beginning of the pattern matches the left context</li>
   * <li>the string from the end of the pattern matches the right context</li>
   * <li>logical is ALL and all languages are in scope; or</li>
   * <li>logical is any other value and at least one language is in scope</li>
   * </ul>
   * <p>
   * Rules are typically generated by parsing rules resources. In normal use, there will be no need for the user
   * to explicitly construct their own.
   * <p>
   * Rules are immutable and thread-safe.
   * <p>
   * <b>Rules resources</b>
   * <p>
   * Rules are typically loaded from resource files. These are UTF-8 encoded text files. They are systematically
   * named following the pattern:
   * <blockquote>org/apache/commons/codec/language/bm/${NameType#getName}_${RuleType#getName}_${language}.txt</blockquote>
   * <p>
   * The format of these resources is the following:
   * <ul>
   * <li><b>Rules:</b> whitespace separated, double-quoted strings. There should be 4 columns to each row, and these
   * will be interpreted as:
   * <ol>
   * <li>pattern</li>
   * <li>left context</li>
   * <li>right context</li>
   * <li>phoneme</li>
   * </ol>
   * </li>
   * <li><b>End-of-line comments:</b> Any occurrence of '//' will cause all text following on that line to be discarded
   * as a comment.</li>
   * <li><b>Multi-line comments:</b> Any line starting with '/*' will start multi-line commenting mode. This will skip
   * all content until a line ending in '*' and '/' is found.</li>
   * <li><b>Blank lines:</b> All blank lines will be skipped.</li>
   * </ul>
   *
   * @since 1.6
   * @version $Id: Rule.html 889935 2013-12-11 05:05:13Z ggregory $
   */
  public class Rule {
  
      public static final class Phoneme implements PhonemeExpr {
          public static final Comparator<Phoneme> COMPARATOR = new Comparator<Phoneme>() {
              @Override
              public int compare(final Phoneme o1, final Phoneme o2) {
                  for (int i = 0; i < o1.phonemeText.length(); i++) {
                      if (i >= o2.phonemeText.length()) {
                          return +1;
                      }
                      final int c = o1.phonemeText.charAt(i) - o2.phonemeText.charAt(i);
                      if (c != 0) {
                          return c;
                      }
                  }
  
                  if (o1.phonemeText.length() < o2.phonemeText.length()) {
                      return -1;
                  }
  
                 return 0;
             }
         };
 
         private final CharSequence phonemeText;
         private final Languages.LanguageSet languages;
 
         public Phoneme(final CharSequence phonemeText, final Languages.LanguageSet languages) {
             this.phonemeText = phonemeText;
             this.languages = languages;
         }
 
         public Phoneme append(final CharSequence str) {
             return new Phoneme(this.phonemeText.toString() + str.toString(), this.languages);
         }
 
         public Languages.LanguageSet getLanguages() {
             return this.languages;
         }
 
         @Override
         public Iterable<Phoneme> getPhonemes() {
             return Collections.singleton(this);
         }
 
         public CharSequence getPhonemeText() {
             return this.phonemeText;
         }
 
         public Phoneme join(final Phoneme right) {
             return new Phoneme(this.phonemeText.toString() + right.phonemeText.toString(),
                                this.languages.restrictTo(right.languages));
         }
     }
 
     public interface PhonemeExpr {
         Iterable<Phoneme> getPhonemes();
     }
 
     public static final class PhonemeList implements PhonemeExpr {
         private final List<Phoneme> phonemes;
 
         public PhonemeList(final List<Phoneme> phonemes) {
             this.phonemes = phonemes;
         }
 
         @Override
         public List<Phoneme> getPhonemes() {
             return this.phonemes;
         }
     }
 
     /**
      * A minimal wrapper around the functionality of Pattern that we use, to allow for alternate implementations.
      */
     public static interface RPattern {
         boolean isMatch(CharSequence input);
     }
 
     public static final RPattern ALL_STRINGS_RMATCHER = new RPattern() {
         @Override
         public boolean isMatch(final CharSequence input) {
             return true;
         }
     };
 
     public static final String ALL = "ALL";
 
     private static final String DOUBLE_QUOTE = "\"";
 
     private static final String HASH_INCLUDE = "#include";
 
     private static final Map<NameType, Map<RuleType, Map<String, List<Rule>>>> RULES =
             new EnumMap<NameType, Map<RuleType, Map<String, List<Rule>>>>(NameType.class);
 
     static {
         for (final NameType s : NameType.values()) {
             final Map<RuleType, Map<String, List<Rule>>> rts =
                     new EnumMap<RuleType, Map<String, List<Rule>>>(RuleType.class);
 
             for (final RuleType rt : RuleType.values()) {
                 final Map<String, List<Rule>> rs = new HashMap<String, List<Rule>>();
 
                 final Languages ls = Languages.getInstance(s);
                 for (final String l : ls.getLanguages()) {
                     try {
                         rs.put(l, parseRules(createScanner(s, rt, l), createResourceName(s, rt, l)));
                     } catch (final IllegalStateException e) {
                         throw new IllegalStateException("Problem processing " + createResourceName(s, rt, l), e);
                     }
                 }
                 if (!rt.equals(RuleType.RULES)) {
                     rs.put("common", parseRules(createScanner(s, rt, "common"), createResourceName(s, rt, "common")));
                 }
 
                 rts.put(rt, Collections.unmodifiableMap(rs));
             }
 
             RULES.put(s, Collections.unmodifiableMap(rts));
         }
     }
 
     private static boolean contains(final CharSequence chars, final char input) {
         for (int i = 0; i < chars.length(); i++) {
             if (chars.charAt(i) == input) {
                 return true;
             }
         }
         return false;
     }
 
     private static String createResourceName(final NameType nameType, final RuleType rt, final String lang) {
         return String.format("org/apache/commons/codec/language/bm/%s_%s_%s.txt",
                              nameType.getName(), rt.getName(), lang);
     }
 
     private static Scanner createScanner(final NameType nameType, final RuleType rt, final String lang) {
         final String resName = createResourceName(nameType, rt, lang);
         final InputStream rulesIS = Languages.class.getClassLoader().getResourceAsStream(resName);
 
         if (rulesIS == null) {
             throw new IllegalArgumentException("Unable to load resource: " + resName);
         }
 
         return new Scanner(rulesIS, ResourceConstants.ENCODING);
     }
 
     private static Scanner createScanner(final String lang) {
         final String resName = String.format("org/apache/commons/codec/language/bm/%s.txt", lang);
         final InputStream rulesIS = Languages.class.getClassLoader().getResourceAsStream(resName);
 
         if (rulesIS == null) {
             throw new IllegalArgumentException("Unable to load resource: " + resName);
         }
 
         return new Scanner(rulesIS, ResourceConstants.ENCODING);
     }
 
     private static boolean endsWith(final CharSequence input, final CharSequence suffix) {
         if (suffix.length() > input.length()) {
             return false;
         }
         for (int i = input.length() - 1, j = suffix.length() - 1; j >= 0; i--, j--) {
             if (input.charAt(i) != suffix.charAt(j)) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      * Gets rules for a combination of name type, rule type and languages.
      *
      * @param nameType
      *            the NameType to consider
      * @param rt
      *            the RuleType to consider
      * @param langs
      *            the set of languages to consider
      * @return a list of Rules that apply
      */
     public static List<Rule> getInstance(final NameType nameType, final RuleType rt,
                                          final Languages.LanguageSet langs) {
         return langs.isSingleton() ? getInstance(nameType, rt, langs.getAny()) :
                                      getInstance(nameType, rt, Languages.ANY);
     }
 
     /**
      * Gets rules for a combination of name type, rule type and a single language.
      *
      * @param nameType
      *            the NameType to consider
      * @param rt
      *            the RuleType to consider
      * @param lang
      *            the language to consider
      * @return a list rules for a combination of name type, rule type and a single language.
      */
     public static List<Rule> getInstance(final NameType nameType, final RuleType rt, final String lang) {
         final List<Rule> rules = RULES.get(nameType).get(rt).get(lang);
 
         if (rules == null) {
             throw new IllegalArgumentException(String.format("No rules found for %s, %s, %s.",
                                                nameType.getName(), rt.getName(), lang));
         }
 
         return rules;
     }
 
     private static Phoneme parsePhoneme(final String ph) {
         final int open = ph.indexOf("[");
         if (open >= 0) {
             if (!ph.endsWith("]")) {
                 throw new IllegalArgumentException("Phoneme expression contains a '[' but does not end in ']'");
             }
             final String before = ph.substring(0, open);
             final String in = ph.substring(open + 1, ph.length() - 1);
             final Set<String> langs = new HashSet<String>(Arrays.asList(in.split("[+]")));
 
             return new Phoneme(before, Languages.LanguageSet.from(langs));
         } else {
             return new Phoneme(ph, Languages.ANY_LANGUAGE);
         }
     }
 
     private static PhonemeExpr parsePhonemeExpr(final String ph) {
         if (ph.startsWith("(")) { // we have a bracketed list of options
             if (!ph.endsWith(")")) {
                 throw new IllegalArgumentException("Phoneme starts with '(' so must end with ')'");
             }
 
             final List<Phoneme> phs = new ArrayList<Phoneme>();
             final String body = ph.substring(1, ph.length() - 1);
             for (final String part : body.split("[|]")) {
                 phs.add(parsePhoneme(part));
             }
             if (body.startsWith("|") || body.endsWith("|")) {
                 phs.add(new Phoneme("", Languages.ANY_LANGUAGE));
             }
 
             return new PhonemeList(phs);
         } else {
             return parsePhoneme(ph);
         }
     }
 
     private static List<Rule> parseRules(final Scanner scanner, final String location) {
         final List<Rule> lines = new ArrayList<Rule>();
         int currentLine = 0;
 
         boolean inMultilineComment = false;
         while (scanner.hasNextLine()) {
             currentLine++;
             final String rawLine = scanner.nextLine();
             String line = rawLine;
 
             if (inMultilineComment) {
                 if (line.endsWith(ResourceConstants.EXT_CMT_END)) {
                     inMultilineComment = false;
                 }
             } else {
                 if (line.startsWith(ResourceConstants.EXT_CMT_START)) {
                     inMultilineComment = true;
                 } else {
                     // discard comments
                     final int cmtI = line.indexOf(ResourceConstants.CMT);
                     if (cmtI >= 0) {
                         line = line.substring(0, cmtI);
                     }
 
                     // trim leading-trailing whitespace
                     line = line.trim();
 
                     if (line.length() == 0) {
                         continue; // empty lines can be safely skipped
                     }
 
                     if (line.startsWith(HASH_INCLUDE)) {
                         // include statement
                         final String incl = line.substring(HASH_INCLUDE.length()).trim();
                         if (incl.contains(" ")) {
                             throw new IllegalArgumentException("Malformed import statement '" + rawLine + "' in " +
                                                                location);
                         } else {
                             lines.addAll(parseRules(createScanner(incl), location + "->" + incl));
                         }
                     } else {
                         // rule
                         final String[] parts = line.split("\\s+");
                         if (parts.length != 4) {
                             throw new IllegalArgumentException("Malformed rule statement split into " + parts.length +
                                                                " parts: " + rawLine + " in " + location);
                         } else {
                             try {
                                 final String pat = stripQuotes(parts[0]);
                                 final String lCon = stripQuotes(parts[1]);
                                 final String rCon = stripQuotes(parts[2]);
                                 final PhonemeExpr ph = parsePhonemeExpr(stripQuotes(parts[3]));
                                 final int cLine = currentLine;
                                 final Rule r = new Rule(pat, lCon, rCon, ph) {
                                     private final int myLine = cLine;
                                     private final String loc = location;
 
                                     @Override
                                     public String toString() {
                                         final StringBuilder sb = new StringBuilder();
                                         sb.append("Rule");
                                         sb.append("{line=").append(myLine);
                                         sb.append(", loc='").append(loc).append('\'');
                                         sb.append('}');
                                         return sb.toString();
                                     }
                                 };
                                 lines.add(r);
                             } catch (final IllegalArgumentException e) {
                                 throw new IllegalStateException("Problem parsing line '" + currentLine + "' in " +
                                                                 location, e);
                             }
                         }
                     }
                 }
             }
         }
 
         return lines;
     }
 
     /**
      * Attempts to compile the regex into direct string ops, falling back to Pattern and Matcher in the worst case.
      *
      * @param regex
      *            the regular expression to compile
      * @return an RPattern that will match this regex
      */
     private static RPattern pattern(final String regex) {
         final boolean startsWith = regex.startsWith("^");
         final boolean endsWith = regex.endsWith("$");
         final String content = regex.substring(startsWith ? 1 : 0, endsWith ? regex.length() - 1 : regex.length());
         final boolean boxes = content.contains("[");
 
         if (!boxes) {
             if (startsWith && endsWith) {
                 // exact match
                 if (content.length() == 0) {
                     // empty
                     return new RPattern() {
                         @Override
                         public boolean isMatch(final CharSequence input) {
                             return input.length() == 0;
                         }
                     };
                 } else {
                     return new RPattern() {
                         @Override
                         public boolean isMatch(final CharSequence input) {
                             return input.equals(content);
                         }
                     };
                 }
             } else if ((startsWith || endsWith) && content.length() == 0) {
                 // matches every string
                 return ALL_STRINGS_RMATCHER;
             } else if (startsWith) {
                 // matches from start
                 return new RPattern() {
                     @Override
                     public boolean isMatch(final CharSequence input) {
                         return startsWith(input, content);
                     }
                 };
             } else if (endsWith) {
                 // matches from start
                 return new RPattern() {
                     @Override
                     public boolean isMatch(final CharSequence input) {
                         return endsWith(input, content);
                     }
                 };
             }
         } else {
             final boolean startsWithBox = content.startsWith("[");
             final boolean endsWithBox = content.endsWith("]");
 
             if (startsWithBox && endsWithBox) {
                 String boxContent = content.substring(1, content.length() - 1);
                 if (!boxContent.contains("[")) {
                     // box containing alternatives
                     final boolean negate = boxContent.startsWith("^");
                     if (negate) {
                         boxContent = boxContent.substring(1);
                     }
                     final String bContent = boxContent;
                     final boolean shouldMatch = !negate;
 
                     if (startsWith && endsWith) {
                         // exact match
                         return new RPattern() {
                             @Override
                             public boolean isMatch(final CharSequence input) {
                                 return input.length() == 1 && contains(bContent, input.charAt(0)) == shouldMatch;
                             }
                         };
                     } else if (startsWith) {
                         // first char
                         return new RPattern() {
                             @Override
                             public boolean isMatch(final CharSequence input) {
                                 return input.length() > 0 && contains(bContent, input.charAt(0)) == shouldMatch;
                             }
                         };
                     } else if (endsWith) {
                         // last char
                         return new RPattern() {
                             @Override
                             public boolean isMatch(final CharSequence input) {
                                 return input.length() > 0 &&
                                        contains(bContent, input.charAt(input.length() - 1)) == shouldMatch;
                             }
                         };
                     }
                 }
             }
         }
 
         return new RPattern() {
             Pattern pattern = Pattern.compile(regex);
 
             @Override
             public boolean isMatch(final CharSequence input) {
                 final Matcher matcher = pattern.matcher(input);
                 return matcher.find();
             }
         };
     }
 
     private static boolean startsWith(final CharSequence input, final CharSequence prefix) {
         if (prefix.length() > input.length()) {
             return false;
         }
         for (int i = 0; i < prefix.length(); i++) {
             if (input.charAt(i) != prefix.charAt(i)) {
                 return false;
             }
         }
         return true;
     }
 
     private static String stripQuotes(String str) {
         if (str.startsWith(DOUBLE_QUOTE)) {
             str = str.substring(1);
         }
 
         if (str.endsWith(DOUBLE_QUOTE)) {
             str = str.substring(0, str.length() - 1);
         }
 
         return str;
     }
 
     private final RPattern lContext;
 
     private final String pattern;
 
     private final PhonemeExpr phoneme;
 
     private final RPattern rContext;
 
     /**
      * Creates a new rule.
      *
      * @param pattern
      *            the pattern
      * @param lContext
      *            the left context
      * @param rContext
      *            the right context
      * @param phoneme
      *            the resulting phoneme
      */
     public Rule(final String pattern, final String lContext, final String rContext, final PhonemeExpr phoneme) {
         this.pattern = pattern;
         this.lContext = pattern(lContext + "$");
         this.rContext = pattern("^" + rContext);
         this.phoneme = phoneme;
     }
 
     /**
      * Gets the left context. This is a regular expression that must match to the left of the pattern.
      *
      * @return the left context Pattern
      */
     public RPattern getLContext() {
         return this.lContext;
     }
 
     /**
      * Gets the pattern. This is a string-literal that must exactly match.
      *
      * @return the pattern
      */
     public String getPattern() {
         return this.pattern;
     }
 
     /**
      * Gets the phoneme. If the rule matches, this is the phoneme associated with the pattern match.
      *
      * @return the phoneme
      */
     public PhonemeExpr getPhoneme() {
         return this.phoneme;
     }
 
     /**
      * Gets the right context. This is a regular expression that must match to the right of the pattern.
      *
      * @return the right context Pattern
      */
     public RPattern getRContext() {
         return this.rContext;
     }
 
     /**
      * Decides if the pattern and context match the input starting at a position. It is a match if the
      * <code>lContext</code> matches <code>input</code> up to <code>i</code>, <code>pattern</code> matches at i and
      * <code>rContext</code> matches from the end of the match of <code>pattern</code> to the end of <code>input</code>.
      *
      * @param input
      *            the input String
      * @param i
      *            the int position within the input
      * @return true if the pattern and left/right context match, false otherwise
      */
     public boolean patternAndContextMatches(final CharSequence input, final int i) {
         if (i < 0) {
             throw new IndexOutOfBoundsException("Can not match pattern at negative indexes");
         }
 
         final int patternLength = this.pattern.length();
         final int ipl = i + patternLength;
 
         if (ipl > input.length()) {
             // not enough room for the pattern to match
             return false;
         }
 
         // evaluate the pattern, left context and right context
         // fail early if any of the evaluations is not successful
         if (!input.subSequence(i, ipl).equals(this.pattern)) {
             return false;
         } else if (!this.rContext.isMatch(input.subSequence(ipl, input.length()))) {
             return false;
         }
         return this.lContext.isMatch(input.subSequence(0, i));
     }
 }