// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

// Global constants.
class _Const {
  // Bytes for "HTTP".
  static final HTTP = const [72, 84, 84, 80];
  // Bytes for "HTTP/1.".
  static final HTTP1DOT = const [72, 84, 84, 80, 47, 49, 46];
  // Bytes for "HTTP/1.0".
  static final HTTP10 = const [72, 84, 84, 80, 47, 49, 46, 48];
  // Bytes for "HTTP/1.1".
  static final HTTP11 = const [72, 84, 84, 80, 47, 49, 46, 49];

  static final END_CHUNKED = const [0x30, 13, 10, 13, 10];

  // Bytes for '()<>@,;:\\"/[]?={} \t'.
  static final SEPARATORS = const [40, 41, 60, 62, 64, 44, 59, 58, 92, 34, 47,
                                   91, 93, 63, 61, 123, 125, 32, 9];

  // Bytes for '()<>@,;:\\"/[]?={} \t\r\n'.
  static final SEPARATORS_AND_CR_LF = const [40, 41, 60, 62, 64, 44, 59, 58, 92,
                                             34, 47, 91, 93, 63, 61, 123, 125,
                                             32, 9, 13, 10];
}


// Frequently used character codes.
class _CharCode {
  static final int HT = 9;
  static final int LF = 10;
  static final int CR = 13;
  static final int SP = 32;
  static final int COMMA = 44;
  static final int DASH = 45;
  static final int SLASH = 47;
  static final int ZERO = 48;
  static final int ONE = 49;
  static final int COLON = 58;
  static final int SEMI_COLON = 59;
}


// States of the HTTP parser state machine.
class _State {
  static final int START = 0;
  static final int METHOD_OR_RESPONSE_HTTP_VERSION = 1;
  static final int RESPONSE_HTTP_VERSION = 2;
  static final int REQUEST_LINE_METHOD = 3;
  static final int REQUEST_LINE_URI = 4;
  static final int REQUEST_LINE_HTTP_VERSION = 5;
  static final int REQUEST_LINE_ENDING = 6;
  static final int RESPONSE_LINE_STATUS_CODE = 7;
  static final int RESPONSE_LINE_REASON_PHRASE = 8;
  static final int RESPONSE_LINE_ENDING = 9;
  static final int HEADER_START = 10;
  static final int HEADER_FIELD = 11;
  static final int HEADER_VALUE_START = 12;
  static final int HEADER_VALUE = 13;
  static final int HEADER_VALUE_FOLDING_OR_ENDING = 14;
  static final int HEADER_VALUE_FOLD_OR_END = 15;
  static final int HEADER_ENDING = 16;

  static final int CHUNK_SIZE_STARTING_CR = 17;
  static final int CHUNK_SIZE_STARTING_LF = 18;
  static final int CHUNK_SIZE = 19;
  static final int CHUNK_SIZE_EXTENSION = 20;
  static final int CHUNK_SIZE_ENDING = 21;
  static final int CHUNKED_BODY_DONE_CR = 22;
  static final int CHUNKED_BODY_DONE_LF = 23;
  static final int BODY = 24;
  static final int CLOSED = 25;
  static final int UPGRADED = 26;
  static final int FAILURE = 27;

  static final int FIRST_BODY_STATE = CHUNK_SIZE_STARTING_CR;
}

// HTTP version of the request or response being parsed.
class _HttpVersion {
  static final int UNDETERMINED = 0;
  static final int HTTP10 = 1;
  static final int HTTP11 = 2;
}

// States of the HTTP parser state machine.
class _MessageType {
  static final int UNDETERMINED = 0;
  static final int REQUEST = 1;
  static final int RESPONSE = 0;
}


/**
 * HTTP parser which parses the HTTP stream as data is supplied
 * through the [:writeList:] and [:connectionClosed:] methods. As the
 * data is parsed the following callbacks are called:
 *
 *   [:requestStart:]
 *   [:responseStart:]
 *   [:headerReceived:]
 *   [:headersComplete:]
 *   [:dataReceived:]
 *   [:dataEnd:]
 *   [:error:]
 *
 * If an HTTP parser error occours it is possible to get an exception
 * thrown from the [:writeList:] and [:connectionClosed:] methods if
 * the error callback is not set.
 *
 * The connection upgrades (e.g. switching from HTTP/1.1 to the
 * WebSocket protocol) is handled in a special way. If connection
 * upgrade is specified in the headers, then on the callback to
 * [:headersComplete:] the [:upgrade:] property on the [:HttpParser:]
 * object will be [:true:] indicating that from now on the protocol is
 * not HTTP anymore and no more callbacks will happen, that is
 * [:dataReceived:] and [:dataEnd:] are not called in this case as
 * there is no more HTTP data. After the upgrade the call to
 * [:writeList:] causing the upgrade will return with the number of
 * bytes parsed as HTTP. Any unparsed bytes is part of the protocol
 * the connection is upgrading to and should be handled according to
 * that protocol.
 */
class _HttpParser {
  _HttpParser() {
    _reset();
  }

  // From RFC 2616.
  // generic-message = start-line
  //                   *(message-header CRLF)
  //                   CRLF
  //                   [ message-body ]
  // start-line      = Request-Line | Status-Line
  // Request-Line    = Method SP Request-URI SP HTTP-Version CRLF
  // Status-Line     = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
  // message-header  = field-name ":" [ field-value ]
  int writeList(List<int> buffer, int offset, int count) {
    int index = offset;
    int lastIndex = offset + count;
    try {
      if (_state == _State.CLOSED) {
        throw new HttpParserException("Data on closed connection");
      }
      if (_state == _State.UPGRADED) {
        throw new HttpParserException("Data on upgraded connection");
      }
      if (_state == _State.FAILURE) {
        throw new HttpParserException("Data on failed connection");
      }
      while ((index < lastIndex) &&
             _state != _State.FAILURE &&
             _state != _State.UPGRADED) {
        int byte = buffer[index];
        switch (_state) {
          case _State.START:
            if (byte == _Const.HTTP[0]) {
              // Start parsing method or HTTP version.
              _httpVersionIndex = 1;
              _state = _State.METHOD_OR_RESPONSE_HTTP_VERSION;
            } else {
              // Start parsing method.
              if (!_isTokenChar(byte)) {
                throw new HttpParserException("Invalid request method");
              }
              _method_or_status_code.addCharCode(byte);
              _state = _State.REQUEST_LINE_METHOD;
            }
            break;

          case _State.METHOD_OR_RESPONSE_HTTP_VERSION:
            if (_httpVersionIndex < _Const.HTTP.length &&
                byte == _Const.HTTP[_httpVersionIndex]) {
              // Continue parsing HTTP version.
              _httpVersionIndex++;
            } else if (_httpVersionIndex == _Const.HTTP.length &&
                       byte == _CharCode.SLASH) {
              // HTTP/ parsed. As method is a token this cannot be a
              // method anymore.
              _httpVersionIndex++;
              _state = _State.RESPONSE_HTTP_VERSION;
            } else {
              // Did not parse HTTP version. Expect method instead.
              for (int i = 0; i < _httpVersionIndex; i++) {
                _method_or_status_code.addCharCode(_Const.HTTP[i]);
              }
              if (byte == _CharCode.SP) {
                _state = _State.REQUEST_LINE_URI;
              } else {
                _method_or_status_code.addCharCode(byte);
                _httpVersion = _HttpVersion.UNDETERMINED;
                _state = _State.REQUEST_LINE_METHOD;
              }
            }
            break;

          case _State.RESPONSE_HTTP_VERSION:
            if (_httpVersionIndex < _Const.HTTP1DOT.length) {
              // Continue parsing HTTP version.
              _expect(byte, _Const.HTTP1DOT[_httpVersionIndex]);
              _httpVersionIndex++;
            } else if (_httpVersionIndex == _Const.HTTP1DOT.length &&
                       byte == _CharCode.ONE) {
              // HTTP/1.1 parsed.
              _httpVersion = _HttpVersion.HTTP11;
              _persistentConnection = true;
              _httpVersionIndex++;
            } else if (_httpVersionIndex == _Const.HTTP1DOT.length &&
                       byte == _CharCode.ZERO) {
              // HTTP/1.0 parsed.
              _httpVersion = _HttpVersion.HTTP10;
              _persistentConnection = false;
              _httpVersionIndex++;
            } else if (_httpVersionIndex == _Const.HTTP1DOT.length + 1) {
              _expect(byte, _CharCode.SP);
              // HTTP version parsed.
              _state = _State.RESPONSE_LINE_STATUS_CODE;
            } else {
              throw new HttpParserException("Invalid response line");
            }
            break;

          case _State.REQUEST_LINE_METHOD:
            if (byte == _CharCode.SP) {
              _state = _State.REQUEST_LINE_URI;
            } else {
              if (_Const.SEPARATORS_AND_CR_LF.indexOf(byte) != -1) {
                throw new HttpParserException("Invalid request method");
              }
              _method_or_status_code.addCharCode(byte);
            }
            break;

          case _State.REQUEST_LINE_URI:
            if (byte == _CharCode.SP) {
              _state = _State.REQUEST_LINE_HTTP_VERSION;
              _httpVersionIndex = 0;
            } else {
              if (byte == _CharCode.CR || byte == _CharCode.LF) {
                throw new HttpParserException("Invalid request URI");
              }
              _uri_or_reason_phrase.addCharCode(byte);
            }
            break;

          case _State.REQUEST_LINE_HTTP_VERSION:
            if (_httpVersionIndex < _Const.HTTP1DOT.length) {
              _expect(byte, _Const.HTTP11[_httpVersionIndex]);
              _httpVersionIndex++;
            } else if (_httpVersionIndex == _Const.HTTP1DOT.length) {
              if (byte == _CharCode.ONE) {
                // HTTP/1.1 parsed.
                _httpVersion = _HttpVersion.HTTP11;
                _persistentConnection = true;
                _httpVersionIndex++;
              } else if (byte == _CharCode.ZERO) {
                // HTTP/1.0 parsed.
                _httpVersion = _HttpVersion.HTTP10;
                _persistentConnection = false;
                _httpVersionIndex++;
              } else {
                throw new HttpParserException("Invalid response line");
              }
            } else {
              _expect(byte, _CharCode.CR);
              _state = _State.REQUEST_LINE_ENDING;
            }
            break;

          case _State.REQUEST_LINE_ENDING:
            _expect(byte, _CharCode.LF);
            _messageType = _MessageType.REQUEST;
            if (requestStart != null) {
              requestStart(_method_or_status_code.toString(),
                           _uri_or_reason_phrase.toString(),
                           version);
            }
            _method_or_status_code.clear();
            _uri_or_reason_phrase.clear();
            _state = _State.HEADER_START;
            break;

          case _State.RESPONSE_LINE_STATUS_CODE:
            if (byte == _CharCode.SP) {
              if (_method_or_status_code.length != 3) {
                throw new HttpParserException("Invalid response status code");
              }
              _state = _State.RESPONSE_LINE_REASON_PHRASE;
            } else {
              if (byte < 0x30 && 0x39 < byte) {
                throw new HttpParserException("Invalid response status code");
              } else {
                _method_or_status_code.addCharCode(byte);
              }
            }
            break;

          case _State.RESPONSE_LINE_REASON_PHRASE:
            if (byte == _CharCode.CR) {
              if (_uri_or_reason_phrase.length == 0) {
                throw new HttpParserException("Invalid response reason phrase");
              }
              _state = _State.RESPONSE_LINE_ENDING;
            } else {
              if (byte == _CharCode.CR || byte == _CharCode.LF) {
                throw new HttpParserException("Invalid response reason phrase");
              }
              _uri_or_reason_phrase.addCharCode(byte);
            }
            break;

          case _State.RESPONSE_LINE_ENDING:
            _expect(byte, _CharCode.LF);
            _messageType == _MessageType.RESPONSE;
            int statusCode = Math.parseInt(_method_or_status_code.toString());
            if (statusCode < 100 || statusCode > 599) {
              throw new HttpParserException("Invalid response status code");
            } else {
              // Check whether this response will never have a body.
              _noMessageBody =
                  statusCode <= 199 || statusCode == 204 || statusCode == 304;
            }
            if (responseStart != null) {
              responseStart(statusCode, _uri_or_reason_phrase.toString(), version);
            }
            _method_or_status_code.clear();
            _uri_or_reason_phrase.clear();
            _state = _State.HEADER_START;
            break;

          case _State.HEADER_START:
            if (byte == _CharCode.CR) {
              _state = _State.HEADER_ENDING;
            } else {
              // Start of new header field.
              _headerField.addCharCode(_toLowerCase(byte));
              _state = _State.HEADER_FIELD;
            }
            break;

          case _State.HEADER_FIELD:
            if (byte == _CharCode.COLON) {
              _state = _State.HEADER_VALUE_START;
            } else {
              if (!_isTokenChar(byte)) {
                throw new HttpParserException("Invalid header field name");
              }
              _headerField.addCharCode(_toLowerCase(byte));
            }
            break;

          case _State.HEADER_VALUE_START:
            if (byte == _CharCode.CR) {
              _state = _State.HEADER_VALUE_FOLDING_OR_ENDING;
            } else if (byte != _CharCode.SP && byte != _CharCode.HT) {
              // Start of new header value.
              _headerValue.addCharCode(byte);
              _state = _State.HEADER_VALUE;
            }
            break;

          case _State.HEADER_VALUE:
            if (byte == _CharCode.CR) {
              _state = _State.HEADER_VALUE_FOLDING_OR_ENDING;
            } else {
              _headerValue.addCharCode(byte);
            }
            break;

          case _State.HEADER_VALUE_FOLDING_OR_ENDING:
            _expect(byte, _CharCode.LF);
            _state = _State.HEADER_VALUE_FOLD_OR_END;
            break;

          case _State.HEADER_VALUE_FOLD_OR_END:
            if (byte == _CharCode.SP || byte == _CharCode.HT) {
              _state = _State.HEADER_VALUE_START;
            } else {
              String headerField = _headerField.toString();
              String headerValue =_headerValue.toString();
              bool reportHeader = true;
              if (headerField == "content-length" && !_chunked) {
                // Ignore the Content-Length header if Transfer-Encoding
                // is chunked (RFC 2616 section 4.4)
                _contentLength = Math.parseInt(headerValue);
              } else if (headerField == "connection") {
                List<String> tokens = _tokenizeFieldValue(headerValue);
                for (int i = 0; i < tokens.length; i++) {
                  String token = tokens[i].toLowerCase();
                  if (token == "keep-alive") {
                    _persistentConnection = true;
                  } else if (token == "close") {
                    _persistentConnection = false;
                  } else if (token == "upgrade") {
                    _connectionUpgrade = true;
                  }
                  if (headerReceived != null) {
                    headerReceived(headerField, token);
                  }
                }
                reportHeader = false;
              } else if (headerField == "transfer-encoding" &&
                         headerValue.toLowerCase() == "chunked") {
                // Ignore the Content-Length header if Transfer-Encoding
                // is chunked (RFC 2616 section 4.4)
                _chunked = true;
                _contentLength = -1;
              }
              if (reportHeader && headerReceived != null) {
                headerReceived(headerField, headerValue);
              }
              _headerField.clear();
              _headerValue.clear();

              if (byte == _CharCode.CR) {
                _state = _State.HEADER_ENDING;
              } else {
                // Start of new header field.
                _headerField.addCharCode(_toLowerCase(byte));
                _state = _State.HEADER_FIELD;
              }
            }
            break;

          case _State.HEADER_ENDING:
            _expect(byte, _CharCode.LF);
            if (_connectionUpgrade) {
              _state = _State.UPGRADED;
              _unparsedData =
                  buffer.getRange(index + 1, count - (index + 1 - offset));
              if (headersComplete != null) headersComplete();
            } else {
              if (headersComplete != null) headersComplete();
              if (_chunked) {
                _state = _State.CHUNK_SIZE;
                _remainingContent = 0;
              } else if (_contentLength == 0 ||
                         (_messageType == _MessageType.REQUEST &&
                          _contentLength == -1) ||
                         (_messageType == _MessageType.RESPONSE &&
                          (_noMessageBody || _responseToMethod == "HEAD"))) {
                // If there is no message body get ready to process the
                // next request.
                _bodyEnd();
                _reset();
              } else if (_contentLength > 0) {
                _remainingContent = _contentLength;
                _state = _State.BODY;
              } else {
                // Neither chunked nor content length. End of body
                // indicated by close.
                _state = _State.BODY;
              }
            }
            break;

          case _State.CHUNK_SIZE_STARTING_CR:
            _expect(byte, _CharCode.CR);
            _state = _State.CHUNK_SIZE_STARTING_LF;
            break;

          case _State.CHUNK_SIZE_STARTING_LF:
            _expect(byte, _CharCode.LF);
            _state = _State.CHUNK_SIZE;
            break;

          case _State.CHUNK_SIZE:
            if (byte == _CharCode.CR) {
              _state = _State.CHUNK_SIZE_ENDING;
            } else if (byte == _CharCode.SEMI_COLON) {
              _state = _State.CHUNK_SIZE_EXTENSION;
            } else {
              int value = _expectHexDigit(byte);
              _remainingContent = _remainingContent * 16 + value;
            }
            break;

          case _State.CHUNK_SIZE_EXTENSION:
            if (byte == _CharCode.CR) {
              _state = _State.CHUNK_SIZE_ENDING;
            }
            break;

          case _State.CHUNK_SIZE_ENDING:
            _expect(byte, _CharCode.LF);
            if (_remainingContent > 0) {
              _state = _State.BODY;
            } else {
              _state = _State.CHUNKED_BODY_DONE_CR;
            }
            break;

          case _State.CHUNKED_BODY_DONE_CR:
            _expect(byte, _CharCode.CR);
            _state = _State.CHUNKED_BODY_DONE_LF;
            break;

          case _State.CHUNKED_BODY_DONE_LF:
            _expect(byte, _CharCode.LF);
            _bodyEnd();
            _reset();
            break;

          case _State.BODY:
            // The body is not handled one byte at a time but in blocks.
            int dataAvailable = lastIndex - index;
            List<int> data;
            if (_remainingContent == null ||
                dataAvailable <= _remainingContent) {
              data = new Uint8List(dataAvailable);
              data.setRange(0, dataAvailable, buffer, index);
            } else {
              data = new Uint8List(_remainingContent);
              data.setRange(0, _remainingContent, buffer, index);
            }

            if (dataReceived != null) dataReceived(data);
            if (_remainingContent != null) {
              _remainingContent -= data.length;
            }
            index += data.length;
            if (_remainingContent == 0) {
              if (!_chunked) {
                _bodyEnd();
                _reset();
              } else {
                _state = _State.CHUNK_SIZE_STARTING_CR;
              }
            }

            // Hack - as we always do index++ below.
            index--;
            break;

          case _state = _State.FAILURE:
            // Should be unreachable.
            assert(false);
            break;

          default:
            // Should be unreachable.
            assert(false);
            break;
        }

        // Move to the next byte.
        index++;
      }
    } catch (var e) {
      // Report the error through the error callback if any. Otherwise
      // throw the error.
      if (error != null) {
        error(e);
        _state = _State.FAILURE;
      } else {
        throw e;
      }
    }

    // Return the number of bytes parsed.
    return index - offset;
  }

  int connectionClosed() {
    if (_state < _State.FIRST_BODY_STATE) {
      _state = _State.FAILURE;
      // Report the error through the error callback if any. Otherwise
      // throw the error.
      var e = new HttpParserException(
          "Connection closed before full header was received");
      if (error != null) {
        error(e);
        return;
      }
      throw e;
    }

    if (!_chunked && _contentLength == -1) {
      if (_state != _State.START) {
        if (dataEnd != null) dataEnd(true);
      }
      _state = _State.CLOSED;
    } else {
      _state = _State.FAILURE;
      // Report the error through the error callback if any. Otherwise
      // throw the error.
      var e = new HttpParserException(
          "Connection closed before full body was received");
      if (error != null) {
        error(e);
        return;
      }
      throw e;
    }
  }

  String get version() {
    switch (_httpVersion) {
      case _HttpVersion.HTTP10:
        return "1.0";
        break;
      case _HttpVersion.HTTP11:
        return "1.1";
        break;
    }
    return null;
  }

  int get messageType() => _messageType;
  int get contentLength() => _contentLength;
  bool get upgrade() => _connectionUpgrade && _state == _State.UPGRADED;
  bool get persistentConnection() => _persistentConnection;

  void set responseToMethod(String method) { _responseToMethod = method; }

  bool get isIdle() => _state == _State.START;

  List<int> get unparsedData() => _unparsedData;

  void _bodyEnd() {
    if (dataEnd != null) {
      dataEnd(_messageType == _MessageType.RESPONSE && !_persistentConnection);
    }
  }

  _reset() {
    _state = _State.START;
    _messageType = _MessageType.UNDETERMINED;
    _headerField = new StringBuffer();
    _headerValue = new StringBuffer();
    _method_or_status_code = new StringBuffer();
    _uri_or_reason_phrase = new StringBuffer();

    _httpVersion = _HttpVersion.UNDETERMINED;
    _contentLength = -1;
    _persistentConnection = false;
    _connectionUpgrade = false;
    _chunked = false;

    _noMessageBody = false;
    _responseToMethod = null;
    _remainingContent = null;
  }

  bool _isTokenChar(int byte) {
    return byte > 31 && byte < 128 && _Const.SEPARATORS.indexOf(byte) == -1;
  }

  List<String> _tokenizeFieldValue(String headerValue) {
    List<String> tokens = new List<String>();
    int start = 0;
    int index = 0;
    while (index < headerValue.length) {
      if (headerValue[index] == ",") {
        tokens.add(headerValue.substring(start, index));
        start = index + 1;
      } else if (headerValue[index] == " " || headerValue[index] == "\t") {
        start++;
      }
      index++;
    }
    tokens.add(headerValue.substring(start, index));
    return tokens;
  }

  int _toLowerCase(int byte) {
    final int aCode = "A".charCodeAt(0);
    final int zCode = "Z".charCodeAt(0);
    final int delta = "a".charCodeAt(0) - aCode;
    return (aCode <= byte && byte <= zCode) ? byte + delta : byte;
  }

  int _expect(int val1, int val2) {
    if (val1 != val2) {
      throw new HttpParserException("Failed to parse HTTP");
    }
  }

  int _expectHexDigit(int byte) {
    if (0x30 <= byte && byte <= 0x39) {
      return byte - 0x30;  // 0 - 9
    } else if (0x41 <= byte && byte <= 0x46) {
      return byte - 0x41 + 10;  // A - F
    } else if (0x61 <= byte && byte <= 0x66) {
      return byte - 0x61 + 10;  // a - f
    } else {
      throw new HttpParserException("Failed to parse HTTP");
    }
  }

  int _state;
  int _httpVersionIndex;
  int _messageType;
  StringBuffer _method_or_status_code;
  StringBuffer _uri_or_reason_phrase;
  StringBuffer _headerField;
  StringBuffer _headerValue;

  int _httpVersion;
  int _contentLength;
  bool _persistentConnection;
  bool _connectionUpgrade;
  bool _chunked;

  bool _noMessageBody;
  String _responseToMethod;  // Indicates the method used for the request.
  int _remainingContent;

  List<int> _unparsedData;  // Unparsed data after connection upgrade.
  // Callbacks.
  Function requestStart;
  Function responseStart;
  Function headerReceived;
  Function headersComplete;
  Function dataReceived;
  Function dataEnd;
  Function error;
}


class HttpParserException implements Exception {
  const HttpParserException([String this.message = ""]);
  String toString() => "HttpParserException: $message";
  final String message;
}