/*
    * ====================================================================
    * 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.List;
  
  import org.apache.http.HeaderElement;
  import org.apache.http.NameValuePair;
  import org.apache.http.ParseException;
  import org.apache.http.annotation.Immutable;
  import org.apache.http.protocol.HTTP;
  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
   */
  @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
          BasicHeaderValueParser DEFAULT = new BasicHeaderValueParser();
  
      public final static BasicHeaderValueParser INSTANCE = new BasicHeaderValueParser();
  
      private final static char PARAM_DELIMITER                = ';';
      private final static char ELEM_DELIMITER                 = ',';
      private final static char[] ALL_DELIMITERS               = new char[] {
                                                                  PARAM_DELIMITER,
                                                                  ELEM_DELIMITER
                                                                  };
  
      public BasicHeaderValueParser() {
          super();
      }
  
      /**
       * Parses elements with the given parser.
       *
       * @param value     the header value to parse
       * @param parser    the parser to use, or <code>null</code> for default
       *
       * @return  array holding the header elements, never <code>null</code>
       */
      public final static
          HeaderElement[] parseElements(final String value,
                                        HeaderValueParser parser) throws ParseException {
          Args.notNull(value, "Value");
          if (parser == null) {
              parser = BasicHeaderValueParser.INSTANCE;
          }
  
          final CharArrayBuffer buffer = new CharArrayBuffer(value.length());
          buffer.append(value);
          final ParserCursor cursor = new ParserCursor(0, value.length());
          return parser.parseElements(buffer, cursor);
      }
  
  
      // non-javadoc, see interface HeaderValueParser
     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().length() == 0 && 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</code> for default
      *
      * @return  the parsed header element
      */
     public final static
         HeaderElement parseHeaderElement(final String value,
                                          HeaderValueParser parser) throws ParseException {
         Args.notNull(value, "Value");
         if (parser == null) {
             parser = BasicHeaderValueParser.INSTANCE;
         }
 
         final CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         final ParserCursor cursor = new ParserCursor(0, value.length());
         return parser.parseHeaderElement(buffer, cursor);
     }
 
 
     // non-javadoc, see interface HeaderValueParser
     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</code> for default
      *
      * @return  array holding the parameters, never <code>null</code>
      */
     public final static
         NameValuePair[] parseParameters(final String value,
                                         HeaderValueParser parser) throws ParseException {
         Args.notNull(value, "Value");
         if (parser == null) {
             parser = BasicHeaderValueParser.INSTANCE;
         }
 
         final CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         final ParserCursor cursor = new ParserCursor(0, value.length());
         return parser.parseParameters(buffer, cursor);
     }
 
 
 
     // non-javadoc, see interface HeaderValueParser
     public NameValuePair[] parseParameters(final CharArrayBuffer buffer,
                                            final ParserCursor cursor) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
         int pos = cursor.getPos();
         final int indexTo = cursor.getUpperBound();
 
         while (pos < indexTo) {
             final char ch = buffer.charAt(pos);
             if (HTTP.isWhitespace(ch)) {
                 pos++;
             } else {
                 break;
             }
         }
         cursor.updatePos(pos);
         if (cursor.atEnd()) {
             return new NameValuePair[] {};
         }
 
         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</code> for default
      *
      * @return  the parsed name-value pair
      */
     public final static
        NameValuePair parseNameValuePair(final String value,
                                         HeaderValueParser parser) throws ParseException {
         Args.notNull(value, "Value");
         if (parser == null) {
             parser = BasicHeaderValueParser.INSTANCE;
         }
 
         final CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         final ParserCursor cursor = new ParserCursor(0, value.length());
         return parser.parseNameValuePair(buffer, cursor);
     }
 
 
     // non-javadoc, see interface HeaderValueParser
     public NameValuePair parseNameValuePair(final CharArrayBuffer buffer,
                                             final ParserCursor cursor) {
         return parseNameValuePair(buffer, cursor, ALL_DELIMITERS);
     }
 
     private static boolean isOneOf(final char ch, final char[] chs) {
         if (chs != null) {
             for (final char ch2 : chs) {
                 if (ch == ch2) {
                     return true;
                 }
             }
         }
         return false;
     }
 
     public NameValuePair parseNameValuePair(final CharArrayBuffer buffer,
                                             final ParserCursor cursor,
                                             final char[] delimiters) {
         Args.notNull(buffer, "Char array buffer");
         Args.notNull(cursor, "Parser cursor");
 
         boolean terminated = false;
 
         int pos = cursor.getPos();
         final int indexFrom = cursor.getPos();
         final int indexTo = cursor.getUpperBound();
 
         // Find name
         String name = null;
         while (pos < indexTo) {
             final char ch = buffer.charAt(pos);
             if (ch == '=') {
                 break;
             }
             if (isOneOf(ch, delimiters)) {
                 terminated = true;
                 break;
             }
             pos++;
         }
 
         if (pos == indexTo) {
             terminated = true;
             name = buffer.substringTrimmed(indexFrom, indexTo);
         } else {
             name = buffer.substringTrimmed(indexFrom, pos);
             pos++;
         }
 
         if (terminated) {
             cursor.updatePos(pos);
             return createNameValuePair(name, null);
         }
 
         // Find value
         String value = null;
         int i1 = pos;
 
         boolean qouted = false;
         boolean escaped = false;
         while (pos < indexTo) {
             final char ch = buffer.charAt(pos);
             if (ch == '"' && !escaped) {
                 qouted = !qouted;
             }
             if (!qouted && !escaped && isOneOf(ch, delimiters)) {
                 terminated = true;
                 break;
             }
             if (escaped) {
                 escaped = false;
             } else {
                 escaped = qouted && ch == '\\';
             }
             pos++;
         }
 
         int i2 = pos;
         // Trim leading white spaces
         while (i1 < i2 && (HTTP.isWhitespace(buffer.charAt(i1)))) {
             i1++;
         }
         // Trim trailing white spaces
         while ((i2 > i1) && (HTTP.isWhitespace(buffer.charAt(i2 - 1)))) {
             i2--;
         }
         // Strip away quotes if necessary
         if (((i2 - i1) >= 2)
             && (buffer.charAt(i1) == '"')
             && (buffer.charAt(i2 - 1) == '"')) {
             i1++;
             i2--;
         }
         value = buffer.substring(i1, i2);
         if (terminated) {
             pos++;
         }
         cursor.updatePos(pos);
         return createNameValuePair(name, value);
     }
 
     /**
      * Creates a name-value pair.
      * Called from {@link #parseNameValuePair}.
      *
      * @param name      the name
      * @param value     the value, or <code>null</code>
      *
      * @return  a name-value pair representing the arguments
      */
     protected NameValuePair createNameValuePair(final String name, final String value) {
         return new BasicNameValuePair(name, value);
     }
 
 }