/*
    * ====================================================================
    * 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.hc.core5.http.message;
  
  import java.util.ArrayList;
  import java.util.BitSet;
  import java.util.List;
  
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.http.HeaderElement;
  import org.apache.hc.core5.http.NameValuePair;
  import org.apache.hc.core5.util.Args;
  import org.apache.hc.core5.util.Tokenizer;
  
  /**
   * Default {@link org.apache.hc.core5.http.message.HeaderValueParser} implementation.
   *
   * @since 4.0
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  public class BasicHeaderValueParser implements HeaderValueParser {
  
      public final static BasicHeaderValueParseraderValueParser.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 = Tokenizer.INIT_BITSET('=', PARAM_DELIMITER, ELEM_DELIMITER);
      private static final BitSet VALUE_DELIMS = Tokenizer.INIT_BITSET(PARAM_DELIMITER, ELEM_DELIMITER);
  
      private final Tokenizer tokenizer;
  
      public BasicHeaderValueParser() {
          this.tokenizer = Tokenizer.INSTANCE;
      }
  
      /**
       * An empty immutable {@code HeaderElement} array.
       */
      private static final HeaderElementlement">HeaderElement[] EMPTY_HEADER_ELEMENT_ARRAY = new HeaderElement[0];
  
      /**
       * An empty immutable {@code NameValuePair} array.
       */
      private static final NameValuePaireValuePair">NameValuePair[] EMPTY_NAME_VALUE_ARRAY = new NameValuePair[0];
  
      @Override
      public HeaderElement[] parseElements(final CharSequence buffer, final ParserCursor cursor) {
          Args.notNull(buffer, "Char sequence");
          Args.notNull(cursor, "Parser cursor");
          final List<HeaderElement> elements = new ArrayList<>();
          while (!cursor.atEnd()) {
              final HeaderElement element = parseHeaderElement(buffer, cursor);
              if (!(element.getName().isEmpty() && element.getValue() == null)) {
                  elements.add(element);
              }
          }
          return elements.toArray(EMPTY_HEADER_ELEMENT_ARRAY);
      }
  
      @Override
      public HeaderElement parseHeaderElement(final CharSequence buffer, final ParserCursor cursor) {
          Args.notNull(buffer, "Char sequence");
          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 new BasicHeaderElement(nvp.getName(), nvp.getValue(), params);
     }
 
     @Override
     public NameValuePair[] parseParameters(final CharSequence buffer, final ParserCursor cursor) {
         Args.notNull(buffer, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         tokenizer.skipWhiteSpace(buffer, cursor);
         final List<NameValuePair> params = new ArrayList<>();
         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(EMPTY_NAME_VALUE_ARRAY);
     }
 
     @Override
     public NameValuePair parseNameValuePair(final CharSequence buffer, final ParserCursor cursor) {
         Args.notNull(buffer, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
 
         final String name = tokenizer.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 new BasicNameValuePair(name, null);
         }
         final String value = tokenizer.parseValue(buffer, cursor, VALUE_DELIMS);
         if (!cursor.atEnd()) {
             cursor.updatePos(cursor.getPos() + 1);
         }
         return new BasicNameValuePair(name, value);
     }
 
 }