/*
    * ====================================================================
    * 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 org.apache.http.HttpVersion;
  import org.apache.http.ProtocolVersion;
  import org.apache.http.ParseException;
  import org.apache.http.RequestLine;
  import org.apache.http.StatusLine;
  import org.apache.http.Header;
  import org.apache.http.annotation.Immutable;
  import org.apache.http.protocol.HTTP;
  import org.apache.http.util.CharArrayBuffer;
  
  /**
   * Basic parser for lines in the head section of an HTTP message.
   * There are individual methods for parsing a request line, a
   * status line, or a header line.
   * The lines to parse are passed in memory, the parser does not depend
   * on any specific IO mechanism.
   * Instances of this class are stateless and thread-safe.
   * Derived classes MUST maintain these properties.
   *
   * <p>
   * Note: This class was created by refactoring parsing code located in
   * various other classes. The author tags from those other classes have
   * been replicated here, although the association with the parsing code
   * taken from there has not been traced.
   * </p>
   *
   * @since 4.0
   */
  @Immutable
  public class BasicLineParser implements LineParser {
  
      /**
       * A default instance of this class, for use as default or fallback.
       * Note that {@link BasicLineParser} 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.
       */
      public final static BasicLineParser DEFAULT = new BasicLineParser();
  
  
      /**
       * A version of the protocol to parse.
       * The version is typically not relevant, but the protocol name.
       */
      protected final ProtocolVersion protocol;
  
  
      /**
       * Creates a new line parser for the given HTTP-like protocol.
       *
       * @param proto     a version of the protocol to parse, or
       *                  <code>null</code> for HTTP. The actual version
       *                  is not relevant, only the protocol name.
       */
      public BasicLineParser(ProtocolVersion proto) {
          if (proto == null) {
              proto = HttpVersion.HTTP_1_1;
          }
          this.protocol = proto;
      }
  
  
      /**
       * Creates a new line parser for HTTP.
       */
      public BasicLineParser() {
          this(null);
      }
  
  
     public final static
         ProtocolVersion parseProtocolVersion(String value,
                                              LineParser parser)
         throws ParseException {
 
         if (value == null) {
             throw new IllegalArgumentException
                 ("Value to parse may not be null.");
         }
 
         if (parser == null)
             parser = BasicLineParser.DEFAULT;
 
         CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         ParserCursor cursor = new ParserCursor(0, value.length());
         return parser.parseProtocolVersion(buffer, cursor);
     }
 
 
     // non-javadoc, see interface LineParser
     public ProtocolVersion parseProtocolVersion(final CharArrayBuffer buffer,
                                                 final ParserCursor cursor)
         throws ParseException {
 
         if (buffer == null) {
             throw new IllegalArgumentException("Char array buffer may not be null");
         }
         if (cursor == null) {
             throw new IllegalArgumentException("Parser cursor may not be null");
         }
 
         final String protoname = this.protocol.getProtocol();
         final int protolength  = protoname.length();
 
         int indexFrom = cursor.getPos();
         int indexTo = cursor.getUpperBound();
 
         skipWhitespace(buffer, cursor);
 
         int i = cursor.getPos();
 
         // long enough for "HTTP/1.1"?
         if (i + protolength + 4 > indexTo) {
             throw new ParseException
                 ("Not a valid protocol version: " +
                  buffer.substring(indexFrom, indexTo));
         }
 
         // check the protocol name and slash
         boolean ok = true;
         for (int j=0; ok && (j<protolength); j++) {
             ok = (buffer.charAt(i+j) == protoname.charAt(j));
         }
         if (ok) {
             ok = (buffer.charAt(i+protolength) == '/');
         }
         if (!ok) {
             throw new ParseException
                 ("Not a valid protocol version: " +
                  buffer.substring(indexFrom, indexTo));
         }
 
         i += protolength+1;
 
         int period = buffer.indexOf('.', i, indexTo);
         if (period == -1) {
             throw new ParseException
                 ("Invalid protocol version number: " +
                  buffer.substring(indexFrom, indexTo));
         }
         int major;
         try {
             major = Integer.parseInt(buffer.substringTrimmed(i, period));
         } catch (NumberFormatException e) {
             throw new ParseException
                 ("Invalid protocol major version number: " +
                  buffer.substring(indexFrom, indexTo));
         }
         i = period + 1;
 
         int blank = buffer.indexOf(' ', i, indexTo);
         if (blank == -1) {
             blank = indexTo;
         }
         int minor;
         try {
             minor = Integer.parseInt(buffer.substringTrimmed(i, blank));
         } catch (NumberFormatException e) {
             throw new ParseException(
                 "Invalid protocol minor version number: " +
                 buffer.substring(indexFrom, indexTo));
         }
 
         cursor.updatePos(blank);
 
         return createProtocolVersion(major, minor);
 
     } // parseProtocolVersion
 
 
     /**
      * Creates a protocol version.
      * Called from {@link #parseProtocolVersion}.
      *
      * @param major     the major version number, for example 1 in HTTP/1.0
      * @param minor     the minor version number, for example 0 in HTTP/1.0
      *
      * @return  the protocol version
      */
     protected ProtocolVersion createProtocolVersion(int major, int minor) {
         return protocol.forVersion(major, minor);
     }
 
 
 
     // non-javadoc, see interface LineParser
     public boolean hasProtocolVersion(final CharArrayBuffer buffer,
                                       final ParserCursor cursor) {
 
         if (buffer == null) {
             throw new IllegalArgumentException("Char array buffer may not be null");
         }
         if (cursor == null) {
             throw new IllegalArgumentException("Parser cursor may not be null");
         }
         int index = cursor.getPos();
 
         final String protoname = this.protocol.getProtocol();
         final int  protolength = protoname.length();
 
         if (buffer.length() < protolength+4)
             return false; // not long enough for "HTTP/1.1"
 
         if (index < 0) {
             // end of line, no tolerance for trailing whitespace
             // this works only for single-digit major and minor version
             index = buffer.length() -4 -protolength;
         } else if (index == 0) {
             // beginning of line, tolerate leading whitespace
             while ((index < buffer.length()) &&
                     HTTP.isWhitespace(buffer.charAt(index))) {
                  index++;
              }
         } // else within line, don't tolerate whitespace
 
 
         if (index + protolength + 4 > buffer.length())
             return false;
 
 
         // just check protocol name and slash, no need to analyse the version
         boolean ok = true;
         for (int j=0; ok && (j<protolength); j++) {
             ok = (buffer.charAt(index+j) == protoname.charAt(j));
         }
         if (ok) {
             ok = (buffer.charAt(index+protolength) == '/');
         }
 
         return ok;
     }
 
 
 
     public final static
         RequestLine parseRequestLine(final String value,
                                      LineParser parser)
         throws ParseException {
 
         if (value == null) {
             throw new IllegalArgumentException
                 ("Value to parse may not be null.");
         }
 
         if (parser == null)
             parser = BasicLineParser.DEFAULT;
 
         CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         ParserCursor cursor = new ParserCursor(0, value.length());
         return parser.parseRequestLine(buffer, cursor);
     }
 
 
     /**
      * Parses a request line.
      *
      * @param buffer    a buffer holding the line to parse
      *
      * @return  the parsed request line
      *
      * @throws ParseException        in case of a parse error
      */
     public RequestLine parseRequestLine(final CharArrayBuffer buffer,
                                         final ParserCursor cursor)
         throws ParseException {
 
         if (buffer == null) {
             throw new IllegalArgumentException("Char array buffer may not be null");
         }
         if (cursor == null) {
             throw new IllegalArgumentException("Parser cursor may not be null");
         }
 
         int indexFrom = cursor.getPos();
         int indexTo = cursor.getUpperBound();
 
         try {
             skipWhitespace(buffer, cursor);
             int i = cursor.getPos();
 
             int blank = buffer.indexOf(' ', i, indexTo);
             if (blank < 0) {
                 throw new ParseException("Invalid request line: " +
                         buffer.substring(indexFrom, indexTo));
             }
             String method = buffer.substringTrimmed(i, blank);
             cursor.updatePos(blank);
 
             skipWhitespace(buffer, cursor);
             i = cursor.getPos();
 
             blank = buffer.indexOf(' ', i, indexTo);
             if (blank < 0) {
                 throw new ParseException("Invalid request line: " +
                         buffer.substring(indexFrom, indexTo));
             }
             String uri = buffer.substringTrimmed(i, blank);
             cursor.updatePos(blank);
 
             ProtocolVersion ver = parseProtocolVersion(buffer, cursor);
 
             skipWhitespace(buffer, cursor);
             if (!cursor.atEnd()) {
                 throw new ParseException("Invalid request line: " +
                         buffer.substring(indexFrom, indexTo));
             }
 
             return createRequestLine(method, uri, ver);
         } catch (IndexOutOfBoundsException e) {
             throw new ParseException("Invalid request line: " +
                                      buffer.substring(indexFrom, indexTo));
         }
     } // parseRequestLine
 
 
     /**
      * Instantiates a new request line.
      * Called from {@link #parseRequestLine}.
      *
      * @param method    the request method
      * @param uri       the requested URI
      * @param ver       the protocol version
      *
      * @return  a new status line with the given data
      */
     protected RequestLine createRequestLine(final String method,
                                             final String uri,
                                             final ProtocolVersion ver) {
         return new BasicRequestLine(method, uri, ver);
     }
 
 
 
     public final static
         StatusLine parseStatusLine(final String value,
                                    LineParser parser)
         throws ParseException {
 
         if (value == null) {
             throw new IllegalArgumentException
                 ("Value to parse may not be null.");
         }
 
         if (parser == null)
             parser = BasicLineParser.DEFAULT;
 
         CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         ParserCursor cursor = new ParserCursor(0, value.length());
         return parser.parseStatusLine(buffer, cursor);
     }
 
 
     // non-javadoc, see interface LineParser
     public StatusLine parseStatusLine(final CharArrayBuffer buffer,
                                       final ParserCursor cursor)
         throws ParseException {
 
         if (buffer == null) {
             throw new IllegalArgumentException("Char array buffer may not be null");
         }
         if (cursor == null) {
             throw new IllegalArgumentException("Parser cursor may not be null");
         }
 
         int indexFrom = cursor.getPos();
         int indexTo = cursor.getUpperBound();
 
         try {
             // handle the HTTP-Version
             ProtocolVersion ver = parseProtocolVersion(buffer, cursor);
 
             // handle the Status-Code
             skipWhitespace(buffer, cursor);
             int i = cursor.getPos();
 
             int blank = buffer.indexOf(' ', i, indexTo);
             if (blank < 0) {
                 blank = indexTo;
             }
             int statusCode = 0;
             String s = buffer.substringTrimmed(i, blank);
             for (int j = 0; j < s.length(); j++) {
                 if (!Character.isDigit(s.charAt(j))) {
                     throw new ParseException(
                             "Status line contains invalid status code: "
                             + buffer.substring(indexFrom, indexTo));
                 }
             }
             try {
                 statusCode = Integer.parseInt(s);
             } catch (NumberFormatException e) {
                 throw new ParseException(
                         "Status line contains invalid status code: "
                         + buffer.substring(indexFrom, indexTo));
             }
             //handle the Reason-Phrase
             i = blank;
             String reasonPhrase = null;
             if (i < indexTo) {
                 reasonPhrase = buffer.substringTrimmed(i, indexTo);
             } else {
                 reasonPhrase = "";
             }
             return createStatusLine(ver, statusCode, reasonPhrase);
 
         } catch (IndexOutOfBoundsException e) {
             throw new ParseException("Invalid status line: " +
                                      buffer.substring(indexFrom, indexTo));
         }
     } // parseStatusLine
 
 
     /**
      * Instantiates a new status line.
      * Called from {@link #parseStatusLine}.
      *
      * @param ver       the protocol version
      * @param status    the status code
      * @param reason    the reason phrase
      *
      * @return  a new status line with the given data
      */
     protected StatusLine createStatusLine(final ProtocolVersion ver,
                                           final int status,
                                           final String reason) {
         return new BasicStatusLine(ver, status, reason);
     }
 
 
 
     public final static
         Header parseHeader(final String value,
                            LineParser parser)
         throws ParseException {
 
         if (value == null) {
             throw new IllegalArgumentException
                 ("Value to parse may not be null");
         }
 
         if (parser == null)
             parser = BasicLineParser.DEFAULT;
 
         CharArrayBuffer buffer = new CharArrayBuffer(value.length());
         buffer.append(value);
         return parser.parseHeader(buffer);
     }
 
 
     // non-javadoc, see interface LineParser
     public Header parseHeader(CharArrayBuffer buffer)
         throws ParseException {
 
         // the actual parser code is in the constructor of BufferedHeader
         return new BufferedHeader(buffer);
     }
 
 
     /**
      * Helper to skip whitespace.
      */
     protected void skipWhitespace(final CharArrayBuffer buffer, final ParserCursor cursor) {
         int pos = cursor.getPos();
         int indexTo = cursor.getUpperBound();
         while ((pos < indexTo) &&
                HTTP.isWhitespace(buffer.charAt(pos))) {
             pos++;
         }
         cursor.updatePos(pos);
     }
 
 } // class BasicLineParser