text: import codecs
  import sys
  import struct
  from hpack.hpack import Encoder, Decoder
  
  from .. import utils
  from functools import reduce
  
  
  class FrameSizeError(Exception):
      pass
  
  
  class Frame(object):
  
      """
          Baseclass Frame
          contains header
          payload is defined in subclasses
      """
  
      FLAG_NO_FLAGS = 0x0
      FLAG_ACK = 0x1
      FLAG_END_STREAM = 0x1
      FLAG_END_HEADERS = 0x4
      FLAG_PADDED = 0x8
      FLAG_PRIORITY = 0x20
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=FLAG_NO_FLAGS,
              stream_id=0x0):
          valid_flags = reduce(lambda x, y: x | y, self.VALID_FLAGS, 0x0)
          if flags | valid_flags != valid_flags:
              raise ValueError('invalid flags detected.')
  
          if state is None:
              class State(object):
                  pass
  
              state = State()
              state.http2_settings = HTTP2_DEFAULT_SETTINGS.copy()
              state.encoder = Encoder()
              state.decoder = Decoder()
  
          self.state = state
  
          self.length = length
          self.type = self.TYPE
          self.flags = flags
          self.stream_id = stream_id
  
      @classmethod
      def _check_frame_size(cls, length, state):
          if state:
              settings = state.http2_settings
          else:
              settings = HTTP2_DEFAULT_SETTINGS.copy()
  
          max_frame_size = settings[
              SettingsFrame.SETTINGS.SETTINGS_MAX_FRAME_SIZE]
  
          if length > max_frame_size:
              raise FrameSizeError(
                  "Frame size exceeded: %d, but only %d allowed." % (
                      length, max_frame_size))
  
      @classmethod
      def from_file(cls, fp, state=None):
          """
            read a HTTP/2 frame sent by a server or client
            fp is a "file like" object that could be backed by a network
            stream or a disk or an in memory stream reader
          """
          raw_header = fp.safe_read(9)
  
          fields = struct.unpack("!HBBBL", raw_header)
          length = (fields[0] << 8) + fields[1]
          flags = fields[3]
          stream_id = fields[4]
  
          if raw_header[:4] == b'HTTP':  # pragma no cover
              print("WARNING: This looks like an HTTP/1 connection!", file=sys.stderr)
  
          cls._check_frame_size(length, state)
  
          payload = fp.safe_read(length)
          return FRAMES[fields[2]].from_bytes(
              state,
              length,
              flags,
              stream_id,
              payload)
  
      def to_bytes(self):
          payload = self.payload_bytes()
          self.length = len(payload)
  
          self._check_frame_size(self.length, self.state)
  
          b = struct.pack('!HB', self.length & 0xFFFF00, self.length & 0x0000FF)
          b += struct.pack('!B', self.TYPE)
          b += struct.pack('!B', self.flags)
          b += struct.pack('!L', self.stream_id & 0x7FFFFFFF)
          b += payload
  
          return b
  
      def payload_bytes(self):  # pragma: no cover
          raise NotImplementedError()
  
      def payload_human_readable(self):  # pragma: no cover
          raise NotImplementedError()
  
      def human_readable(self, direction="-"):
          self.length = len(self.payload_bytes())
  
          return "\n".join([
              "%s: %s | length: %d | flags: %#x | stream_id: %d" % (
              direction, self.__class__.__name__, self.length, self.flags, self.stream_id),
              self.payload_human_readable(),
              "===============================================================",
          ])
  
      def __eq__(self, other):
          return self.to_bytes() == other.to_bytes()
  
  
  class DataFrame(Frame):
      TYPE = 0x0
      VALID_FLAGS = [Frame.FLAG_END_STREAM, Frame.FLAG_PADDED]
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              payload=b'',
              pad_length=0):
          super(DataFrame, self).__init__(state, length, flags, stream_id)
          self.payload = payload
          self.pad_length = pad_length
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          if f.flags & Frame.FLAG_PADDED:
              f.pad_length = payload[0]
              f.payload = payload[1:-f.pad_length]
          else:
              f.payload = payload
  
          return f
  
      def payload_bytes(self):
          if self.stream_id == 0x0:
              raise ValueError('DATA frames MUST be associated with a stream.')
  
          b = b''
          if self.flags & self.FLAG_PADDED:
              b += struct.pack('!B', self.pad_length)
  
          b += bytes(self.payload)
  
          if self.flags & self.FLAG_PADDED:
              b += b'\0' * self.pad_length
  
          return b
  
      def payload_human_readable(self):
          return "payload: %s" % str(self.payload)
  
  
  class HeadersFrame(Frame):
      TYPE = 0x1
      VALID_FLAGS = [
          Frame.FLAG_END_STREAM,
          Frame.FLAG_END_HEADERS,
          Frame.FLAG_PADDED,
          Frame.FLAG_PRIORITY]
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              header_block_fragment=b'',
              pad_length=0,
              exclusive=False,
              stream_dependency=0x0,
              weight=0):
          super(HeadersFrame, self).__init__(state, length, flags, stream_id)
  
          self.header_block_fragment = header_block_fragment
          self.pad_length = pad_length
          self.exclusive = exclusive
          self.stream_dependency = stream_dependency
          self.weight = weight
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          if f.flags & Frame.FLAG_PADDED:
              f.pad_length = payload[0]
              f.header_block_fragment = payload[1:-f.pad_length]
          else:
              f.header_block_fragment = payload[0:]
  
          if f.flags & Frame.FLAG_PRIORITY:
              f.stream_dependency, f.weight = struct.unpack(
                  '!LB', f.header_block_fragment[:5])
              f.exclusive = bool(f.stream_dependency >> 31)
              f.stream_dependency &= 0x7FFFFFFF
              f.header_block_fragment = f.header_block_fragment[5:]
  
          return f
  
      def payload_bytes(self):
          if self.stream_id == 0x0:
              raise ValueError('HEADERS frames MUST be associated with a stream.')
  
          b = b''
          if self.flags & self.FLAG_PADDED:
              b += struct.pack('!B', self.pad_length)
  
          if self.flags & self.FLAG_PRIORITY:
              b += struct.pack('!LB',
                               (int(self.exclusive) << 31) | self.stream_dependency,
                               self.weight)
  
          b += self.header_block_fragment
  
          if self.flags & self.FLAG_PADDED:
              b += b'\0' * self.pad_length
  
          return b
  
      def payload_human_readable(self):
          s = []
  
          if self.flags & self.FLAG_PRIORITY:
              s.append("exclusive: %d" % self.exclusive)
              s.append("stream dependency: %#x" % self.stream_dependency)
              s.append("weight: %d" % self.weight)
  
          if self.flags & self.FLAG_PADDED:
              s.append("padding: %d" % self.pad_length)
  
          s.append(
              "header_block_fragment: %s" %
              codecs.encode(self.header_block_fragment, 'hex'))
  
          return "\n".join(s)
  
  
  class PriorityFrame(Frame):
      TYPE = 0x2
      VALID_FLAGS = []
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              exclusive=False,
              stream_dependency=0x0,
              weight=0):
          super(PriorityFrame, self).__init__(state, length, flags, stream_id)
          self.exclusive = exclusive
          self.stream_dependency = stream_dependency
          self.weight = weight
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          f.stream_dependency, f.weight = struct.unpack('!LB', payload)
          f.exclusive = bool(f.stream_dependency >> 31)
          f.stream_dependency &= 0x7FFFFFFF
  
          return f
  
      def payload_bytes(self):
          if self.stream_id == 0x0:
              raise ValueError(
                  'PRIORITY frames MUST be associated with a stream.')
  
          if self.stream_dependency == 0x0:
              raise ValueError('stream dependency is invalid.')
  
          return struct.pack(
              '!LB',
              (int(
                  self.exclusive) << 31) | self.stream_dependency,
              self.weight)
  
      def payload_human_readable(self):
          s = []
          s.append("exclusive: %d" % self.exclusive)
          s.append("stream dependency: %#x" % self.stream_dependency)
          s.append("weight: %d" % self.weight)
          return "\n".join(s)
  
  
  class RstStreamFrame(Frame):
      TYPE = 0x3
      VALID_FLAGS = []
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              error_code=0x0):
          super(RstStreamFrame, self).__init__(state, length, flags, stream_id)
          self.error_code = error_code
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
          f.error_code = struct.unpack('!L', payload)[0]
          return f
  
      def payload_bytes(self):
          if self.stream_id == 0x0:
              raise ValueError(
                  'RST_STREAM frames MUST be associated with a stream.')
  
          return struct.pack('!L', self.error_code)
  
      def payload_human_readable(self):
          return "error code: %#x" % self.error_code
  
  
  class SettingsFrame(Frame):
      TYPE = 0x4
      VALID_FLAGS = [Frame.FLAG_ACK]
  
      SETTINGS = utils.BiDi(
          SETTINGS_HEADER_TABLE_SIZE=0x1,
          SETTINGS_ENABLE_PUSH=0x2,
          SETTINGS_MAX_CONCURRENT_STREAMS=0x3,
          SETTINGS_INITIAL_WINDOW_SIZE=0x4,
          SETTINGS_MAX_FRAME_SIZE=0x5,
          SETTINGS_MAX_HEADER_LIST_SIZE=0x6,
      )
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              settings=None):
          super(SettingsFrame, self).__init__(state, length, flags, stream_id)
  
          if settings is None:
              settings = {}
  
          self.settings = settings
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          for i in range(0, len(payload), 6):
              identifier, value = struct.unpack("!HL", payload[i:i + 6])
              f.settings[identifier] = value
  
          return f
  
      def payload_bytes(self):
          if self.stream_id != 0x0:
              raise ValueError(
                  'SETTINGS frames MUST NOT be associated with a stream.')
  
          b = b''
          for identifier, value in list(self.settings.items()):
              b += struct.pack("!HL", identifier & 0xFF, value)
  
          return b
  
      def payload_human_readable(self):
          s = []
  
          for identifier, value in list(self.settings.items()):
              s.append("%s: %#x" % (self.SETTINGS.get_name(identifier), value))
  
          if not s:
              return "settings: None"
          else:
              return "\n".join(s)
  
  
  class PushPromiseFrame(Frame):
      TYPE = 0x5
      VALID_FLAGS = [Frame.FLAG_END_HEADERS, Frame.FLAG_PADDED]
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              promised_stream=0x0,
              header_block_fragment=b'',
              pad_length=0):
          super(PushPromiseFrame, self).__init__(state, length, flags, stream_id)
          self.pad_length = pad_length
          self.promised_stream = promised_stream
          self.header_block_fragment = header_block_fragment
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          if f.flags & Frame.FLAG_PADDED:
              f.pad_length, f.promised_stream = struct.unpack('!BL', payload[:5])
              f.header_block_fragment = payload[5:-f.pad_length]
          else:
              f.promised_stream = int(struct.unpack("!L", payload[:4])[0])
              f.header_block_fragment = payload[4:]
  
          f.promised_stream &= 0x7FFFFFFF
  
          return f
  
      def payload_bytes(self):
          if self.stream_id == 0x0:
              raise ValueError(
                  'PUSH_PROMISE frames MUST be associated with a stream.')
  
          if self.promised_stream == 0x0:
              raise ValueError('Promised stream id not valid.')
  
          b = b''
          if self.flags & self.FLAG_PADDED:
              b += struct.pack('!B', self.pad_length)
  
          b += struct.pack('!L', self.promised_stream & 0x7FFFFFFF)
          b += bytes(self.header_block_fragment)
  
          if self.flags & self.FLAG_PADDED:
              b += b'\0' * self.pad_length
  
          return b
  
      def payload_human_readable(self):
          s = []
  
          if self.flags & self.FLAG_PADDED:
              s.append("padding: %d" % self.pad_length)
  
          s.append("promised stream: %#x" % self.promised_stream)
          s.append(
              "header_block_fragment: %s" %
              codecs.encode(self.header_block_fragment, 'hex'))
  
          return "\n".join(s)
  
  
  class PingFrame(Frame):
      TYPE = 0x6
      VALID_FLAGS = [Frame.FLAG_ACK]
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              payload=b''):
          super(PingFrame, self).__init__(state, length, flags, stream_id)
          self.payload = payload
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
          f.payload = payload
          return f
  
      def payload_bytes(self):
          if self.stream_id != 0x0:
              raise ValueError(
                  'PING frames MUST NOT be associated with a stream.')
  
          b = self.payload[0:8]
          b += b'\0' * (8 - len(b))
          return b
  
      def payload_human_readable(self):
          return "opaque data: %s" % str(self.payload)
  
  
  class GoAwayFrame(Frame):
      TYPE = 0x7
      VALID_FLAGS = []
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              last_stream=0x0,
              error_code=0x0,
              data=b''):
          super(GoAwayFrame, self).__init__(state, length, flags, stream_id)
          self.last_stream = last_stream
          self.error_code = error_code
          self.data = data
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          f.last_stream, f.error_code = struct.unpack("!LL", payload[:8])
          f.last_stream &= 0x7FFFFFFF
          f.data = payload[8:]
  
          return f
  
      def payload_bytes(self):
          if self.stream_id != 0x0:
              raise ValueError(
                  'GOAWAY frames MUST NOT be associated with a stream.')
  
          b = struct.pack('!LL', self.last_stream & 0x7FFFFFFF, self.error_code)
          b += bytes(self.data)
          return b
  
      def payload_human_readable(self):
          s = []
          s.append("last stream: %#x" % self.last_stream)
          s.append("error code: %d" % self.error_code)
          s.append("debug data: %s" % str(self.data))
          return "\n".join(s)
  
  
  class WindowUpdateFrame(Frame):
      TYPE = 0x8
      VALID_FLAGS = []
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              window_size_increment=0x0):
          super(WindowUpdateFrame, self).__init__(state, length, flags, stream_id)
          self.window_size_increment = window_size_increment
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
  
          f.window_size_increment = struct.unpack("!L", payload)[0]
          f.window_size_increment &= 0x7FFFFFFF
  
          return f
  
      def payload_bytes(self):
          if self.window_size_increment <= 0 or self.window_size_increment >= 2 ** 31:
              raise ValueError(
                  'Window Szie Increment MUST be greater than 0 and less than 2^31.')
  
          return struct.pack('!L', self.window_size_increment & 0x7FFFFFFF)
  
      def payload_human_readable(self):
          return "window size increment: %#x" % self.window_size_increment
  
  
  class ContinuationFrame(Frame):
      TYPE = 0x9
      VALID_FLAGS = [Frame.FLAG_END_HEADERS]
  
      def __init__(
              self,
              state=None,
              length=0,
              flags=Frame.FLAG_NO_FLAGS,
              stream_id=0x0,
              header_block_fragment=b''):
          super(ContinuationFrame, self).__init__(state, length, flags, stream_id)
          self.header_block_fragment = header_block_fragment
  
      @classmethod
      def from_bytes(cls, state, length, flags, stream_id, payload):
          f = cls(state=state, length=length, flags=flags, stream_id=stream_id)
          f.header_block_fragment = payload
          return f
  
      def payload_bytes(self):
          if self.stream_id == 0x0:
              raise ValueError(
                  'CONTINUATION frames MUST be associated with a stream.')
  
          return self.header_block_fragment
  
      def payload_human_readable(self):
          s = []
          s.append(
              "header_block_fragment: %s" %
              codecs.encode(self.header_block_fragment, 'hex'))
          return "\n".join(s)
  
  _FRAME_CLASSES = [
      DataFrame,
      HeadersFrame,
      PriorityFrame,
      RstStreamFrame,
      SettingsFrame,
      PushPromiseFrame,
      PingFrame,
      GoAwayFrame,
      WindowUpdateFrame,
      ContinuationFrame
  ]
  FRAMES = {cls.TYPE: cls for cls in _FRAME_CLASSES}
  
  
  HTTP2_DEFAULT_SETTINGS = {
      SettingsFrame.SETTINGS.SETTINGS_HEADER_TABLE_SIZE: 4096,
      SettingsFrame.SETTINGS.SETTINGS_ENABLE_PUSH: 1,
      SettingsFrame.SETTINGS.SETTINGS_MAX_CONCURRENT_STREAMS: None,
      SettingsFrame.SETTINGS.SETTINGS_INITIAL_WINDOW_SIZE: 2 ** 16 - 1,
      SettingsFrame.SETTINGS.SETTINGS_MAX_FRAME_SIZE: 2 ** 14,
      SettingsFrame.SETTINGS.SETTINGS_MAX_HEADER_LIST_SIZE: None,
  }
  