/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.http.message;
  
  import java.util.ArrayList;
  import java.util.BitSet;
  import java.util.List;
  
  import org.apache.http.HeaderElement;
  import org.apache.http.NameValuePair;
  import org.apache.http.ParseException;
  import org.apache.http.annotation.ThreadingBehavior;
  import org.apache.http.annotation.Contract;
  import org.apache.http.util.Args;
  import org.apache.http.util.CharArrayBuffer;
  
  /**
   * Basic implementation for parsing header values into elements.
   * Instances of this class are stateless and thread-safe.
   * Derived classes are expected to maintain these properties.
   *
   * @since 4.0
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  public class BasicHeaderValueParser implements HeaderValueParser {
  
      /**
       * A default instance of this class, for use as default or fallback.
       * Note that {@link BasicHeaderValueParser} is not a singleton, there
       * can be many instances of the class itself and of derived classes.
       * The instance here provides non-customized, default behavior.
       *
       * @deprecated (4.3) use {@link #INSTANCE}
       */
      @Deprecated
      public final static BasicHeaderValueParserr.html#BasicHeaderValueParser">BasicHeaderValueParser DEFAULT = new BasicHeaderValueParser();
  
      public final static BasicHeaderValueParser.html#BasicHeaderValueParser">BasicHeaderValueParser INSTANCE = new BasicHeaderValueParser();
  
      private final static char PARAM_DELIMITER                = ';';
      private final static char ELEM_DELIMITER                 = ',';
  
      // IMPORTANT!
      // These private static variables must be treated as immutable and never exposed outside this class
      private static final BitSet TOKEN_DELIMS = TokenParser.INIT_BITSET('=', PARAM_DELIMITER, ELEM_DELIMITER);
      private static final BitSet VALUE_DELIMS = TokenParser.INIT_BITSET(PARAM_DELIMITER, ELEM_DELIMITER);
  
      private final TokenParser tokenParser;
  
      public BasicHeaderValueParser() {
          this.tokenParser = TokenParser.INSTANCE;
      }
  
      /**
       * Parses elements with the given parser.
       *
       * @param value     the header value to parse
       * @param parser    the parser to use, or {@code null} for default
       *
       * @return  array holding the header elements, never {@code null}
       * @throws ParseException in case of a parsing error
       */
      public static
          HeaderElement[] parseElements(final String value,
                                        final HeaderValueParser parser) throws ParseException {
          Args.notNull(value, "Value");
  
          final CharArrayBufferhtml#CharArrayBuffer">CharArrayBuffer buffer = new CharArrayBuffer(value.length());
          buffer.append(value);
          final ParserCursoror.html#ParserCursor">ParserCursor cursor = new ParserCursor(0, value.length());
          return (parser != null ? parser : BasicHeaderValueParser.INSTANCE)
              .parseElements(buffer, cursor);
      }
  
 
     // non-javadoc, see interface HeaderValueParser
     @Override
     public HeaderElement[] parseElements(final CharArrayBuffer buffer,
                                          final ParserCursor cursor) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
         final List<HeaderElement> elements = new ArrayList<HeaderElement>();
         while (!cursor.atEnd()) {
             final HeaderElement element = parseHeaderElement(buffer, cursor);
             if (!(element.getName().isEmpty() && element.getValue() == null)) {
                 elements.add(element);
             }
         }
         return elements.toArray(new HeaderElement[elements.size()]);
     }
 
 
     /**
      * Parses an element with the given parser.
      *
      * @param value     the header element to parse
      * @param parser    the parser to use, or {@code null} for default
      *
      * @return  the parsed header element
      */
     public static
         HeaderElement parseHeaderElement(final String value,
                                          final HeaderValueParser parser) throws ParseException {
         Args.notNull(value, "Value");
 
         final CharArrayBufferhtml#CharArrayBuffer">CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         final ParserCursoror.html#ParserCursor">ParserCursor cursor = new ParserCursor(0, value.length());
         return (parser != null ? parser : BasicHeaderValueParser.INSTANCE)
                 .parseHeaderElement(buffer, cursor);
     }
 
 
     // non-javadoc, see interface HeaderValueParser
     @Override
     public HeaderElement parseHeaderElement(final CharArrayBuffer buffer,
                                             final ParserCursor cursor) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
         final NameValuePair nvp = parseNameValuePair(buffer, cursor);
         NameValuePair[] params = null;
         if (!cursor.atEnd()) {
             final char ch = buffer.charAt(cursor.getPos() - 1);
             if (ch != ELEM_DELIMITER) {
                 params = parseParameters(buffer, cursor);
             }
         }
         return createHeaderElement(nvp.getName(), nvp.getValue(), params);
     }
 
 
     /**
      * Creates a header element.
      * Called from {@link #parseHeaderElement}.
      *
      * @return  a header element representing the argument
      */
     protected HeaderElement createHeaderElement(
             final String name,
             final String value,
             final NameValuePair[] params) {
         return new BasicHeaderElement(name, value, params);
     }
 
 
     /**
      * Parses parameters with the given parser.
      *
      * @param value     the parameter list to parse
      * @param parser    the parser to use, or {@code null} for default
      *
      * @return  array holding the parameters, never {@code null}
      */
     public static
         NameValuePair[] parseParameters(final String value,
                                         final HeaderValueParser parser) throws ParseException {
         Args.notNull(value, "Value");
 
         final CharArrayBufferhtml#CharArrayBuffer">CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         final ParserCursoror.html#ParserCursor">ParserCursor cursor = new ParserCursor(0, value.length());
         return (parser != null ? parser : BasicHeaderValueParser.INSTANCE)
                 .parseParameters(buffer, cursor);
     }
 
 
 
     // non-javadoc, see interface HeaderValueParser
     @Override
     public NameValuePair[] parseParameters(final CharArrayBuffer buffer,
                                            final ParserCursor cursor) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
         tokenParser.skipWhiteSpace(buffer, cursor);
         final List<NameValuePair> params = new ArrayList<NameValuePair>();
         while (!cursor.atEnd()) {
             final NameValuePair param = parseNameValuePair(buffer, cursor);
             params.add(param);
             final char ch = buffer.charAt(cursor.getPos() - 1);
             if (ch == ELEM_DELIMITER) {
                 break;
             }
         }
         return params.toArray(new NameValuePair[params.size()]);
     }
 
     /**
      * Parses a name-value-pair with the given parser.
      *
      * @param value     the NVP to parse
      * @param parser    the parser to use, or {@code null} for default
      *
      * @return  the parsed name-value pair
      */
     public static
        NameValuePair parseNameValuePair(final String value,
                                         final HeaderValueParser parser) throws ParseException {
         Args.notNull(value, "Value");
 
         final CharArrayBufferhtml#CharArrayBuffer">CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         final ParserCursoror.html#ParserCursor">ParserCursor cursor = new ParserCursor(0, value.length());
         return (parser != null ? parser : BasicHeaderValueParser.INSTANCE)
                 .parseNameValuePair(buffer, cursor);
     }
 
 
     // non-javadoc, see interface HeaderValueParser
     @Override
     public NameValuePair parseNameValuePair(final CharArrayBuffer buffer,
                                             final ParserCursor cursor) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
 
         final String name = tokenParser.parseToken(buffer, cursor, TOKEN_DELIMS);
         if (cursor.atEnd()) {
             return new BasicNameValuePair(name, null);
         }
         final int delim = buffer.charAt(cursor.getPos());
         cursor.updatePos(cursor.getPos() + 1);
         if (delim != '=') {
             return createNameValuePair(name, null);
         }
         final String value = tokenParser.parseValue(buffer, cursor, VALUE_DELIMS);
         if (!cursor.atEnd()) {
             cursor.updatePos(cursor.getPos() + 1);
         }
         return createNameValuePair(name, value);
     }
 
     /**
      * @deprecated (4.4) use {@link org.apache.http.message.TokenParser}
      */
     @Deprecated
     public NameValuePair parseNameValuePair(final CharArrayBuffer buffer,
                                             final ParserCursor cursor,
                                             final char[] delimiters) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
 
         final BitSet delimSet = new BitSet();
         if (delimiters != null) {
             for (final char delimiter: delimiters) {
                 delimSet.set(delimiter);
             }
         }
         delimSet.set('=');
         final String name = tokenParser.parseToken(buffer, cursor, delimSet);
         if (cursor.atEnd()) {
             return new BasicNameValuePair(name, null);
         }
         final int delim = buffer.charAt(cursor.getPos());
         cursor.updatePos(cursor.getPos() + 1);
         if (delim != '=') {
             return createNameValuePair(name, null);
         }
         delimSet.clear('=');
         final String value = tokenParser.parseValue(buffer, cursor, delimSet);
         if (!cursor.atEnd()) {
             cursor.updatePos(cursor.getPos() + 1);
         }
         return createNameValuePair(name, value);
     }
 
     /**
      * Creates a name-value pair.
      * Called from {@link #parseNameValuePair}.
      *
      * @param name      the name
      * @param value     the value, or {@code null}
      *
      * @return  a name-value pair representing the arguments
      */
     protected NameValuePair createNameValuePair(final String name, final String value) {
         return new BasicNameValuePair(name, value);
     }
 
 }