/*
    * 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.util.Collections;
  import java.util.EnumMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import java.util.Scanner;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  import org.apache.commons.codec.Resources;
  
  /**
   * Language codes.
   * <p>
   * Language codes are typically loaded from resource files. These are UTF-8
   * encoded text files. They are systematically named following the pattern:
   * </p>
   * <blockquote>org/apache/commons/codec/language/bm/${{@link NameType#getName()}
   * languages.txt</blockquote>
   * <p>
   * The format of these resources is the following:
   * </p>
   * <ul>
   * <li><b>Language:</b> a single string containing no whitespace</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>
   * <p>
   * Ported from language.php
   * </p>
   * <p>
   * This class is immutable and thread-safe.
   * </p>
   *
   * @since 1.6
   */
  public class Languages {
      // Implementation note: This class is divided into two sections. The first part
      // is a static factory interface that
      // exposes org/apache/commons/codec/language/bm/%s_languages.txt for %s in
      // NameType.* as a list of supported
      // languages, and a second part that provides instance methods for accessing
      // this set for supported languages.
  
      /**
       * A set of languages.
       */
      public static abstract class LanguageSet {
  
          public static LanguageSet from(final Set<String> langs) {
              return langs.isEmpty() ? NO_LANGUAGES : new SomeLanguages(langs);
          }
  
          public abstract boolean contains(String language);
  
          public abstract String getAny();
  
          public abstract boolean isEmpty();
  
          public abstract boolean isSingleton();
  
          abstract LanguageSet merge(LanguageSet other);
  
          public abstract LanguageSet restrictTo(LanguageSet other);
      }
  
      /**
       * Some languages, explicitly enumerated.
       */
      public static final class SomeLanguages extends LanguageSet {
          private final Set<String> languages;
  
          private SomeLanguages(final Set<String> languages) {
              this.languages = Collections.unmodifiableSet(languages);
          }
  
         @Override
         public boolean contains(final String language) {
             return this.languages.contains(language);
         }
 
         @Override
         public String getAny() {
             return this.languages.iterator().next();
         }
 
         public Set<String> getLanguages() {
             return this.languages;
         }
 
         @Override
         public boolean isEmpty() {
             return this.languages.isEmpty();
         }
 
         @Override
         public boolean isSingleton() {
             return this.languages.size() == 1;
         }
 
         @Override
         public LanguageSet merge(final LanguageSet other) {
             if (other == NO_LANGUAGES) {
                 return this;
             }
             if (other == ANY_LANGUAGE) {
                 return other;
             }
             final SomeLanguages someLanguages = (SomeLanguages) other;
             final Set<String> set = new HashSet<>(languages);
             set.addAll(someLanguages.languages);
             return from(set);
         }
 
         @Override
         public LanguageSet restrictTo(final LanguageSet other) {
             if (other == NO_LANGUAGES) {
                 return other;
             }
             if (other == ANY_LANGUAGE) {
                 return this;
             }
             final SomeLanguages someLanguages = (SomeLanguages) other;
             return from(languages.stream().filter(lang -> someLanguages.languages.contains(lang)).collect(Collectors.toSet()));
         }
 
         @Override
         public String toString() {
             return "Languages(" + languages.toString() + ")";
         }
 
     }
 
     public static final String ANY = "any";
 
     private static final Map<NameType, Languages> LANGUAGES = new EnumMap<>(NameType.class);
 
     /**
      * No languages at all.
      */
     public static final LanguageSet NO_LANGUAGES = new LanguageSet() {
         @Override
         public boolean contains(final String language) {
             return false;
         }
 
         @Override
         public String getAny() {
             throw new NoSuchElementException("Can't fetch any language from the empty language set.");
         }
 
         @Override
         public boolean isEmpty() {
             return true;
         }
 
         @Override
         public boolean isSingleton() {
             return false;
         }
 
         @Override
         public LanguageSet merge(final LanguageSet other) {
             return other;
         }
 
         @Override
         public LanguageSet restrictTo(final LanguageSet other) {
             return this;
         }
 
         @Override
         public String toString() {
             return "NO_LANGUAGES";
         }
     };
 
     /**
      * Any/all languages.
      */
     public static final LanguageSet ANY_LANGUAGE = new LanguageSet() {
         @Override
         public boolean contains(final String language) {
             return true;
         }
 
         @Override
         public String getAny() {
             throw new NoSuchElementException("Can't fetch any language from the any language set.");
         }
 
         @Override
         public boolean isEmpty() {
             return false;
         }
 
         @Override
         public boolean isSingleton() {
             return false;
         }
 
         @Override
         public LanguageSet merge(final LanguageSet other) {
             return other;
         }
 
         @Override
         public LanguageSet restrictTo(final LanguageSet other) {
             return other;
         }
 
         @Override
         public String toString() {
             return "ANY_LANGUAGE";
         }
     };
 
     static {
         for (final NameType s : NameType.values()) {
             LANGUAGES.put(s, getInstance(langResourceName(s)));
         }
     }
 
     public static Languages getInstance(final NameType nameType) {
         return LANGUAGES.get(nameType);
     }
 
     public static Languages getInstance(final String languagesResourceName) {
         // read languages list
         final Set<String> ls = new HashSet<>();
         try (final Scanner lsScanner = new Scanner(Resources.getInputStream(languagesResourceName),
                 ResourceConstants.ENCODING)) {
             boolean inExtendedComment = false;
             while (lsScanner.hasNextLine()) {
                 final String line = lsScanner.nextLine().trim();
                 if (inExtendedComment) {
                     if (line.endsWith(ResourceConstants.EXT_CMT_END)) {
                         inExtendedComment = false;
                     }
                 } else if (line.startsWith(ResourceConstants.EXT_CMT_START)) {
                     inExtendedComment = true;
                 } else if (!line.isEmpty()) {
                     ls.add(line);
                 }
             }
             return new Languages(Collections.unmodifiableSet(ls));
         }
     }
 
     private static String langResourceName(final NameType nameType) {
         return String.format("org/apache/commons/codec/language/bm/%s_languages.txt", nameType.getName());
     }
 
     private final Set<String> languages;
 
     private Languages(final Set<String> languages) {
         this.languages = languages;
     }
 
     public Set<String> getLanguages() {
         return this.languages;
     }
 }