text: __all__ = ["MultipartParser", "Part", "PartData", "Events"]
  
  
  from dataclasses import dataclass
  from itertools import chain
  from enum import Enum, auto
  from collections import deque
  
  from wsgiref.headers import Headers
  
  from typing import Union, Generator, List, Tuple
  
  from .utils import to_bytes, parse_options_header
  from .errors import UnexpectedExit, MalformedData
  
  
  class Events(Enum):
      NEED_DATA = auto()
      FINISHED = auto()
  
  
  class States(Enum):
      BUILDING_HEADERS = auto()
      BUILDING_HEADERS_NEED_DATA = auto()
      BUILDING_BODY = auto()
      BUILDING_BODY_NEED_DATA = auto()
      FINISHED = auto()
      ERROR = auto()
  
  
  @dataclass
  class PartData:
      raw: bytearray
      size: int
  
  
  class Part:
      def __init__(self, charset="latin1"):
          self.headerlist = []
          self.headers = None
          self.data = bytearray()
          self.size = 0
          self.disposition = None
          self.name = None
          self.filename = None
          self.content_type = None
          self.charset = charset
  
      @property
      def value(self) -> str:
          """ Data decoded with the specified charset """
          return self.data.decode(self.charset)
  
      @property
      def raw(self) -> bytearray:
          """ Data without decoding """
          return self.data
  
      def buffer(self, part_data) -> None:
          self.data += part_data.raw
          self.size += part_data.size
  
  
  class MultipartParser:
      def __init__(self, boundary, content_length=None, charset="latin1"):
          self.boundary = boundary
          self.separator = b"--" + to_bytes(self.boundary)
          self.terminator = b"--" + to_bytes(self.boundary) + b"--"
  
          self.separator_len = len(self.separator)
  
          self.charset = charset
  
          self.state = States.BUILDING_HEADERS
          self.events_queue = deque()
  
          self.buffer = bytearray()
          self.last_partial_line = None
  
          self.current_part = None
  
          self.expected_part_size = None
          self.current_part_size = 0
  
      def parts(self) -> List[Union[Part, PartData, Events]]:
          return list(self)
  
      def recv(self, chunk) -> None:
          """
          Queue any events parsing chunk may create.
          """
          self._queue_events(chunk)
  
      def parse(self, chunk) -> List[Union[Part, PartData, Events]]:
          """Queue events for the chunk, and return them as a list."""
          self._queue_events(chunk)
          return self.parts()
  
      def next_event(self) -> Union[Part, PartData, Events]:
          """
          Return the next event from the queue.
          If there is no event, request data, unless parsing is complete.
          """
          try:
              return self.events_queue.popleft()
          except IndexError:
              if self.state is not States.FINISHED:
                  return Events.NEED_DATA
              else:
                  return Events.FINISHED
  
      def __enter__(self):
          return self
  
      def __exit__(self, exc_type, exc_value, tb):
          if self.state is not States.FINISHED:
              raise UnexpectedExit("Unexpected end. No terminator line parsed.")
  
      def __iter__(self) -> Generator[Union[Part, PartData, Events], None, None]:
          """
          Yield all events in the queue.
          """
          while True:
              try:
                  event = self.events_queue.popleft()
              except IndexError:
                  break
              else:
                  yield event
  
      def _queue_events(self, chunk) -> None:
          """
          Send the given chunk through the parser based on the current  parser
          state, and add any events that result to the events queue.
          """
          # Prepend the current buffer if there is any and clear the buffer.
          # Carries partial chunks from one chunk parsing to the next.
          if self.state is States.ERROR:
              raise RuntimeError("Cannot use parser in ERROR state.")
  
          if self.buffer:
              chunk = self.buffer + chunk
              self.buffer = bytearray()
          chunk = iter(chunk.splitlines(True))
  
          while True:
              try:
                  # Prepend the buffer between state changes, to carry
                  # separators and terminations between parsing routes.
                  if self.buffer:
                      split_buffer = iter(self.buffer.splitlines(True))
                      chunk = chain(split_buffer, chunk)
                      self.buffer = bytearray()
  
                  # Depending on the parser's current state, attempt to
                  # either build and queue a Part / PartData object, or
                  # queue actionable events.
                  if self.state is States.BUILDING_HEADERS:
                      maybe_part = self._parse_part(chunk)
                      if maybe_part:
                          self.events_queue.append(maybe_part)
  
                  elif self.state is States.BUILDING_BODY:
                      maybe_part_data = self._build_part_data(chunk)
                      if maybe_part_data:
                          self.events_queue.append(maybe_part_data)
  
                  # queue events based on parser state post parse attempt
                  if self.state is States.BUILDING_HEADERS_NEED_DATA:
                      self.events_queue.append(Events.NEED_DATA)
                      self.state = States.BUILDING_HEADERS
                      break
  
                  elif self.state is States.BUILDING_BODY_NEED_DATA:
                      self.events_queue.append(Events.NEED_DATA)
                      self.state = States.BUILDING_BODY
                      break
  
                  elif self.state is States.FINISHED:
                      self.events_queue.append(Events.FINISHED)
                      break
              except Exception:
                  self.state = States.ERROR
                  raise
  
      def _parse_part(self, chunk_lines) -> Union[Part, None]:
          """
          Try to construct and return a Part object, given sufficient
          data in the chunk. If too little data is given, the given data
          will be buffered, and a fresh attempt to create the Part will
          be made upon future request.
          """
          lines = self._separate_newlines(chunk_lines)
  
          # Consume first boundary. Ignore leading blank lines
          maybe_seperator, first_newline = next(
              ((l, nl) for l, nl in lines if l), (b"", b"")
          )
  
  
          if not first_newline:
              # We have not recieved a full line of headers.
              self._buffer_chunk([(maybe_seperator, first_newline)])
              self.state = States.BUILDING_HEADERS_NEED_DATA
              return
  
          if maybe_seperator != self.separator:
              if len(maybe_seperator) >= self.separator_len:
                  raise MalformedData("Part does not start with boundary")
  
          # Buffer the beginning of the part in case we need to reattempt
          # creation later (incomplete data).
          self._buffer_chunk([(maybe_seperator, first_newline)])
  
          self.current_part = self.current_part or Part(charset=self.charset)
          # alias the part so we can return it later and not wipe it
          # with state change
          part = self.current_part
  
          for line, newline in lines:
              self._construct_part(part, line, newline)
  
              if self.state is States.BUILDING_HEADERS_NEED_DATA:
                  self._buffer_chunk([(line, newline)])
                  self._buffer_chunk(lines)
                  break
  
              elif self.state is States.BUILDING_BODY:
                  self.buffer = bytearray()
                  self._buffer_chunk(lines)
                  return part
          else:
              # We have iterated the given data to completion, but have not
              # recieved enough data to build the Part.
              self.state = States.BUILDING_HEADERS_NEED_DATA
  
      def _construct_part(self, part, line, newline) -> None:
          """
          Add headers to the Part as they are parsed.
          """
          line = line.decode(self.charset)
  
          if not newline:
              self.state = States.BUILDING_HEADERS_NEED_DATA
              return
  
          if not line.strip():
              # blank line -> end of header segment
              part.headers = Headers(part.headerlist)
              content_disposition = part.headers.get("Content-Disposition", "")
              content_type = part.headers.get("Content-Type", "")
  
              if not content_disposition:
                  raise MalformedData("Content-Disposition header is missing.")
  
              part.disposition, part.options = parse_options_header(content_disposition)
              part.name = part.options.get("name")
              part.filename = part.options.get("filename")
              part.content_type, options = parse_options_header(content_type)
              part.charset = options.get("charset") or part.charset
  
              content_length = part.headers.get("Content-Length")
              if content_length is not None:
                  self.expected_part_size = int(content_length)
  
              self.current_part = None
              self.state = States.BUILDING_BODY
              return
  
          if ":" not in line:
              raise MalformedData("Syntax error in header: No colon.")
  
          name, value = line.split(":", 1)
          part.headerlist.append((name.strip(), value.strip()))
  
      def _build_part_data(self, chunk_lines) -> Union[PartData, None]:
          """
          Parse through the chunk, creating and returning PartData objects when possible.
          """
          part_data_buffer = bytearray()
  
          lines = self._separate_newlines(chunk_lines)
  
          previous_newline = b""
  
          for line, newline in lines:
              # Handle the case where our last chunk of data ended
              # ambigiously.
              if self.last_partial_line is not None:
                  line = self.last_partial_line + line
                  self.last_partial_line = None
  
              if line == self.terminator:
                  self.state = States.FINISHED
                  self.current_part_size = 0
                  self.expected_part_size = None
                  break
  
              elif line == self.separator:
                  self._buffer_chunk([(line, newline)])
                  self._buffer_chunk(lines)
                  self.state = States.BUILDING_HEADERS
                  self.current_part_size = 0
                  self.expected_part_size = None
                  break
              else:
                  if not newline:
                      # It is impossible to tell the difference between
                      # body data + CRLF + the beginning of the next seperator or
                      # terminator, and random body data. For example, with a terminator
                      # of "--terminator", we can't make a hard decision when our body chunk
                      # is "somedata\r\n--term". We need to hold off on taking any specific
                      # action, instead requesting more data.
                      # We only make a distinction here when there is a possibility
                      # that the chunk could actually be a separator or terminator,
                      # which is when the line is shorter than the sep / term.
                      # Anything else would either pass/fail the sep/term check, or
                      # could not be a sep/term.
                      if len(line) < self.separator_len:
                          self.last_partial_line = line
                          self.state = States.BUILDING_BODY_NEED_DATA
                  else:
                      self._regulate_content_length(len(line))
                      part_data_buffer += previous_newline + line
                      previous_newline = newline
  
          if part_data_buffer:
              if not self.state in (States.BUILDING_HEADERS, States.FINISHED):
                  # we haven't hit an end condition for the current part.
                  self.state = States.BUILDING_BODY_NEED_DATA
              return PartData(raw=part_data_buffer, size=len(part_data_buffer))
  
      def _separate_newlines(self, lines) -> Generator[Tuple[bytes, bytes], None, None]:
          """
          Iterate over a binary file-like object line by line. Each line is
          returned as a (line, line_ending) tuple.
          """
          for line in lines:
              if line.endswith(b"\r\n"):
                  yield line[:-2], b"\r\n"
              elif line.endswith(b"\n"):
                  yield line[:-1], b"\n"
              elif line.endswith(b"\r"):
                  yield line[:-1], b"\r"
              else:
                  yield line or b"", b""
  
      def _buffer_chunk(self, chunk_lines) -> None:
          """
          Take an iterator like Iterable[Tuple[bytes, bytes]] and store them.
          For convenience's sake, we join everything back up as a singular byte string
          for reparsing later.
          """
          self.buffer += b"".join((l + nl) for l, nl in chunk_lines)
  
      def _regulate_content_length(self, line_size) -> None:
          if self.expected_part_size is not None:
              self.current_part_size += line_size
              if self.current_part_size > self.expected_part_size:
                  raise MalformedData("Size of part body exceeds part Content-Length.")
  