__all__ = (
 'StreamReader', 'StreamWriter', 'StreamReaderProtocol',
 'open_connection', 'start_server',
 'IncompleteReadError', 'LimitOverrunError',
)

import socket

if hasattr(socket, 'AF_UNIX'):
 __all__ += ('open_unix_connection', 'start_unix_server')

from . import coroutines
from . import events
from . import protocols
from .log import logger
from .tasks import sleep


_DEFAULT_LIMIT = 2 ** 16 # 64 KiB


class IncompleteReadError(EOFError):
 """
 Incomplete read error. Attributes:

 - partial: read bytes string before the end of stream was reached
 - expected: total number of expected bytes (or None if unknown)
 """
 def __init__(self, partial, expected):
 super().__init__(f'{len(partial)} bytes read on a total of '
 f'{expected!r} expected bytes')
 self.partial = partial
 self.expected = expected

 def __reduce__(self):
 return type(self), (self.partial, self.expected)


class LimitOverrunError(Exception):
 """Reached the buffer limit while looking for a separator.

 Attributes:
 - consumed: total number of to be consumed bytes.
 """
 def __init__(self, message, consumed):
 super().__init__(message)
 self.consumed = consumed

 def __reduce__(self):
 return type(self), (self.args[0], self.consumed)


async def open_connection(host=None, port=None, *,
 loop=None, limit=_DEFAULT_LIMIT, **kwds):
 """A wrapper for create_connection() returning a (reader, writer) pair.

 The reader returned is a StreamReader instance; the writer is a
 StreamWriter instance.

 The arguments are all the usual arguments to create_connection()
 except protocol_factory; most common are positional host and port,
 with various optional keyword arguments following.

 Additional optional keyword arguments are loop (to set the event loop
 instance to use) and limit (to set the buffer limit passed to the
 StreamReader).

 (If you want to customize the StreamReader and/or
 StreamReaderProtocol classes, just copy the code -- there's
 really nothing special here except some convenience.)
 """
 if loop is None:
 loop = events.get_event_loop()
 reader = StreamReader(limit=limit, loop=loop)
 protocol = StreamReaderProtocol(reader, loop=loop)
 transport, _ = await loop.create_connection(
 lambda: protocol, host, port, **kwds)
 writer = StreamWriter(transport, protocol, reader, loop)
 return reader, writer


async def start_server(client_connected_cb, host=None, port=None, *,
 loop=None, limit=_DEFAULT_LIMIT, **kwds):
 """Start a socket server, call back for each client connected.

 The first parameter, `client_connected_cb`, takes two parameters:
 client_reader, client_writer. client_reader is a StreamReader
 object, while client_writer is a StreamWriter object. This
 parameter can either be a plain callback function or a coroutine;
 if it is a coroutine, it will be automatically converted into a
 Task.

 The rest of the arguments are all the usual arguments to
 loop.create_server() except protocol_factory; most common are
 positional host and port, with various optional keyword arguments
 following. The return value is the same as loop.create_server().

 Additional optional keyword arguments are loop (to set the event loop
 instance to use) and limit (to set the buffer limit passed to the
 StreamReader).

 The return value is the same as loop.create_server(), i.e. a
 Server object which can be used to stop the service.
 """
 if loop is None:
 loop = events.get_event_loop()

 def factory():
 reader = StreamReader(limit=limit, loop=loop)
 protocol = StreamReaderProtocol(reader, client_connected_cb,
 loop=loop)
 return protocol

 return await loop.create_server(factory, host, port, **kwds)


if hasattr(socket, 'AF_UNIX'):
 # UNIX Domain Sockets are supported on this platform

 async def open_unix_connection(path=None, *,
 loop=None, limit=_DEFAULT_LIMIT, **kwds):
 """Similar to `open_connection` but works with UNIX Domain Sockets."""
 if loop is None:
 loop = events.get_event_loop()
 reader = StreamReader(limit=limit, loop=loop)
 protocol = StreamReaderProtocol(reader, loop=loop)
 transport, _ = await loop.create_unix_connection(
 lambda: protocol, path, **kwds)
 writer = StreamWriter(transport, protocol, reader, loop)
 return reader, writer

 async def start_unix_server(client_connected_cb, path=None, *,
 loop=None, limit=_DEFAULT_LIMIT, **kwds):
 """Similar to `start_server` but works with UNIX Domain Sockets."""
 if loop is None:
 loop = events.get_event_loop()

 def factory():
 reader = StreamReader(limit=limit, loop=loop)
 protocol = StreamReaderProtocol(reader, client_connected_cb,
 loop=loop)
 return protocol

 return await loop.create_unix_server(factory, path, **kwds)


class FlowControlMixin(protocols.Protocol):
 """Reusable flow control logic for StreamWriter.drain().

 This implements the protocol methods pause_writing(),
 resume_writing() and connection_lost(). If the subclass overrides
 these it must call the super methods.

 StreamWriter.drain() must wait for _drain_helper() coroutine.
 """

 def __init__(self, loop=None):
 if loop is None:
 self._loop = events.get_event_loop()
 else:
 self._loop = loop
 self._paused = False
 self._drain_waiter = None
 self._connection_lost = False

 def pause_writing(self):
 assert not self._paused
 self._paused = True
 if self._loop.get_debug():
 logger.debug("%r pauses writing", self)

 def resume_writing(self):
 assert self._paused
 self._paused = False
 if self._loop.get_debug():
 logger.debug("%r resumes writing", self)

 waiter = self._drain_waiter
 if waiter is not None:
 self._drain_waiter = None
 if not waiter.done():
 waiter.set_result(None)

 def connection_lost(self, exc):
 self._connection_lost = True
 # Wake up the writer if currently paused.
 if not self._paused:
 return
 waiter = self._drain_waiter
 if waiter is None:
 return
 self._drain_waiter = None
 if waiter.done():
 return
 if exc is None:
 waiter.set_result(None)
 else:
 waiter.set_exception(exc)

 async def _drain_helper(self):
 if self._connection_lost:
 raise ConnectionResetError('Connection lost')
 if not self._paused:
 return
 waiter = self._drain_waiter
 assert waiter is None or waiter.cancelled()
 waiter = self._loop.create_future()
 self._drain_waiter = waiter
 await waiter


class StreamReaderProtocol(FlowControlMixin, protocols.Protocol):
 """Helper class to adapt between Protocol and StreamReader.

 (This is a helper class instead of making StreamReader itself a
 Protocol subclass, because the StreamReader has other potential
 uses, and to prevent the user of the StreamReader to accidentally
 call inappropriate methods of the protocol.)
 """

 def __init__(self, stream_reader, client_connected_cb=None, loop=None):
 super().__init__(loop=loop)
 self._stream_reader = stream_reader
 self._stream_writer = None
 self._client_connected_cb = client_connected_cb
 self._over_ssl = False
 self._closed = self._loop.create_future()

 def connection_made(self, transport):
 self._stream_reader.set_transport(transport)
 self._over_ssl = transport.get_extra_info('sslcontext') is not None
 if self._client_connected_cb is not None:
 self._stream_writer = StreamWriter(transport, self,
 self._stream_reader,
 self._loop)
 res = self._client_connected_cb(self._stream_reader,
 self._stream_writer)
 if coroutines.iscoroutine(res):
 self._loop.create_task(res)

 def connection_lost(self, exc):
 if self._stream_reader is not None:
 if exc is None:
 self._stream_reader.feed_eof()
 else:
 self._stream_reader.set_exception(exc)
 if not self._closed.done():
 if exc is None:
 self._closed.set_result(None)
 else:
 self._closed.set_exception(exc)
 super().connection_lost(exc)
 self._stream_reader = None
 self._stream_writer = None

 def data_received(self, data):
 self._stream_reader.feed_data(data)

 def eof_received(self):
 self._stream_reader.feed_eof()
 if self._over_ssl:
 # Prevent a warning in SSLProtocol.eof_received:
 # "returning true from eof_received()
 # has no effect when using ssl"
 return False
 return True

 def __del__(self):
 # Prevent reports about unhandled exceptions.
 # Better than self._closed._log_traceback = False hack
 closed = self._closed
 if closed.done() and not closed.cancelled():
 closed.exception()


class StreamWriter:
 """Wraps a Transport.

 This exposes write(), writelines(), [can_]write_eof(),
 get_extra_info() and close(). It adds drain() which returns an
 optional Future on which you can wait for flow control. It also
 adds a transport property which references the Transport
 directly.
 """

 def __init__(self, transport, protocol, reader, loop):
 self._transport = transport
 self._protocol = protocol
 # drain() expects that the reader has an exception() method
 assert reader is None or isinstance(reader, StreamReader)
 self._reader = reader
 self._loop = loop

 def __repr__(self):
 info = [self.__class__.__name__, f'transport={self._transport!r}']
 if self._reader is not None:
 info.append(f'reader={self._reader!r}')
 return '<{}>'.format(' '.join(info))

 @property
 def transport(self):
 return self._transport

 def write(self, data):
 self._transport.write(data)

 def writelines(self, data):
 self._transport.writelines(data)

 def write_eof(self):
 return self._transport.write_eof()

 def can_write_eof(self):
 return self._transport.can_write_eof()

 def close(self):
 return self._transport.close()

 def is_closing(self):
 return self._transport.is_closing()

 async def wait_closed(self):
 await self._protocol._closed

 def get_extra_info(self, name, default=None):
 return self._transport.get_extra_info(name, default)

 async def drain(self):
 """Flush the write buffer.

 The intended use is to write

 w.write(data)
 await w.drain()
 """
 if self._reader is not None:
 exc = self._reader.exception()
 if exc is not None:
 raise exc
 if self._transport.is_closing():
 # Yield to the event loop so connection_lost() may be
 # called. Without this, _drain_helper() would return
 # immediately, and code that calls
 # write(...); await drain()
 # in a loop would never call connection_lost(), so it
 # would not see an error when the socket is closed.
 await sleep(0, loop=self._loop)
 await self._protocol._drain_helper()


class StreamReader:

 def __init__(self, limit=_DEFAULT_LIMIT, loop=None):
 # The line length limit is a security feature;
 # it also doubles as half the buffer limit.

 if limit <= 0:
 raise ValueError('Limit cannot be <= 0')

 self._limit = limit
 if loop is None:
 self._loop = events.get_event_loop()
 else:
 self._loop = loop
 self._buffer = bytearray()
 self._eof = False # Whether we're done.
 self._waiter = None # A future used by _wait_for_data()
 self._exception = None
 self._transport = None
 self._paused = False

 def __repr__(self):
 info = ['StreamReader']
 if self._buffer:
 info.append(f'{len(self._buffer)} bytes')
 if self._eof:
 info.append('eof')
 if self._limit != _DEFAULT_LIMIT:
 info.append(f'limit={self._limit}')
 if self._waiter:
 info.append(f'waiter={self._waiter!r}')
 if self._exception:
 info.append(f'exception={self._exception!r}')
 if self._transport:
 info.append(f'transport={self._transport!r}')
 if self._paused:
 info.append('paused')
 return '<{}>'.format(' '.join(info))

 def exception(self):
 return self._exception

 def set_exception(self, exc):
 self._exception = exc

 waiter = self._waiter
 if waiter is not None:
 self._waiter = None
 if not waiter.cancelled():
 waiter.set_exception(exc)

 def _wakeup_waiter(self):
 """Wakeup read*() functions waiting for data or EOF."""
 waiter = self._waiter
 if waiter is not None:
 self._waiter = None
 if not waiter.cancelled():
 waiter.set_result(None)

 def set_transport(self, transport):
 assert self._transport is None, 'Transport already set'
 self._transport = transport

 def _maybe_resume_transport(self):
 if self._paused and len(self._buffer) <= self._limit:
 self._paused = False
 self._transport.resume_reading()

 def feed_eof(self):
 self._eof = True
 self._wakeup_waiter()

 def at_eof(self):
 """Return True if the buffer is empty and 'feed_eof' was called."""
 return self._eof and not self._buffer

 def feed_data(self, data):
 assert not self._eof, 'feed_data after feed_eof'

 if not data:
 return

 self._buffer.extend(data)
 self._wakeup_waiter()

 if (self._transport is not None and
 not self._paused and
 len(self._buffer) > 2 * self._limit):
 try:
 self._transport.pause_reading()
 except NotImplementedError:
 # The transport can't be paused.
 # We'll just have to buffer all data.
 # Forget the transport so we don't keep trying.
 self._transport = None
 else:
 self._paused = True

 async def _wait_for_data(self, func_name):
 """Wait until feed_data() or feed_eof() is called.

 If stream was paused, automatically resume it.
 """
 # StreamReader uses a future to link the protocol feed_data() method
 # to a read coroutine. Running two read coroutines at the same time
 # would have an unexpected behaviour. It would not possible to know
 # which coroutine would get the next data.
 if self._waiter is not None:
 raise RuntimeError(
 f'{func_name}() called while another coroutine is '
 f'already waiting for incoming data')

 assert not self._eof, '_wait_for_data after EOF'

 # Waiting for data while paused will make deadlock, so prevent it.
 # This is essential for readexactly(n) for case when n > self._limit.
 if self._paused:
 self._paused = False
 self._transport.resume_reading()

 self._waiter = self._loop.create_future()
 try:
 await self._waiter
 finally:
 self._waiter = None

 async def readline(self):
 """Read chunk of data from the stream until newline (b'\n') is found.

 On success, return chunk that ends with newline. If only partial
 line can be read due to EOF, return incomplete line without
 terminating newline. When EOF was reached while no bytes read, empty
 bytes object is returned.

 If limit is reached, ValueError will be raised. In that case, if
 newline was found, complete line including newline will be removed
 from internal buffer. Else, internal buffer will be cleared. Limit is
 compared against part of the line without newline.

 If stream was paused, this function will automatically resume it if
 needed.
 """
 sep = b'\n'
 seplen = len(sep)
 try:
 line = await self.readuntil(sep)
 except IncompleteReadError as e:
 return e.partial
 except LimitOverrunError as e:
 if self._buffer.startswith(sep, e.consumed):
 del self._buffer[:e.consumed + seplen]
 else:
 self._buffer.clear()
 self._maybe_resume_transport()
 raise ValueError(e.args[0])
 return line

 async def readuntil(self, separator=b'\n'):
 """Read data from the stream until ``separator`` is found.

 On success, the data and separator will be removed from the
 internal buffer (consumed). Returned data will include the
 separator at the end.

 Configured stream limit is used to check result. Limit sets the
 maximal length of data that can be returned, not counting the
 separator.

 If an EOF occurs and the complete separator is still not found,
 an IncompleteReadError exception will be raised, and the internal
 buffer will be reset. The IncompleteReadError.partial attribute
 may contain the separator partially.

 If the data cannot be read because of over limit, a
 LimitOverrunError exception will be raised, and the data
 will be left in the internal buffer, so it can be read again.
 """
 seplen = len(separator)
 if seplen == 0:
 raise ValueError('Separator should be at least one-byte string')

 if self._exception is not None:
 raise self._exception

 # Consume whole buffer except last bytes, which length is
 # one less than seplen. Let's check corner cases with
 # separator='SEPARATOR':
 # * we have received almost complete separator (without last
 # byte). i.e buffer='some textSEPARATO'. In this case we
 # can safely consume len(separator) - 1 bytes.
 # * last byte of buffer is first byte of separator, i.e.
 # buffer='abcdefghijklmnopqrS'. We may safely consume
 # everything except that last byte, but this require to
 # analyze bytes of buffer that match partial separator.
 # This is slow and/or require FSM. For this case our
 # implementation is not optimal, since require rescanning
 # of data that is known to not belong to separator. In
 # real world, separator will not be so long to notice
 # performance problems. Even when reading MIME-encoded
 # messages :)

 # `offset` is the number of bytes from the beginning of the buffer
 # where there is no occurrence of `separator`.
 offset = 0

 # Loop until we find `separator` in the buffer, exceed the buffer size,
 # or an EOF has happened.
 while True:
 buflen = len(self._buffer)

 # Check if we now have enough data in the buffer for `separator` to
 # fit.
 if buflen - offset >= seplen:
 isep = self._buffer.find(separator, offset)

 if isep != -1:
 # `separator` is in the buffer. `isep` will be used later
 # to retrieve the data.
 break

 # see upper comment for explanation.
 offset = buflen + 1 - seplen
 if offset > self._limit:
 raise LimitOverrunError(
 'Separator is not found, and chunk exceed the limit',
 offset)

 # Complete message (with full separator) may be present in buffer
 # even when EOF flag is set. This may happen when the last chunk
 # adds data which makes separator be found. That's why we check for
 # EOF *ater* inspecting the buffer.
 if self._eof:
 chunk = bytes(self._buffer)
 self._buffer.clear()
 raise IncompleteReadError(chunk, None)

 # _wait_for_data() will resume reading if stream was paused.
 await self._wait_for_data('readuntil')

 if isep > self._limit:
 raise LimitOverrunError(
 'Separator is found, but chunk is longer than limit', isep)

 chunk = self._buffer[:isep + seplen]
 del self._buffer[:isep + seplen]
 self._maybe_resume_transport()
 return bytes(chunk)

 async def read(self, n=-1):
 """Read up to `n` bytes from the stream.

 If n is not provided, or set to -1, read until EOF and return all read
 bytes. If the EOF was received and the internal buffer is empty, return
 an empty bytes object.

 If n is zero, return empty bytes object immediately.

 If n is positive, this function try to read `n` bytes, and may return
 less or equal bytes than requested, but at least one byte. If EOF was
 received before any byte is read, this function returns empty byte
 object.

 Returned value is not limited with limit, configured at stream
 creation.

 If stream was paused, this function will automatically resume it if
 needed.
 """

 if self._exception is not None:
 raise self._exception

 if n == 0:
 return b''

 if n < 0:
 # This used to just loop creating a new waiter hoping to
 # collect everything in self._buffer, but that would
 # deadlock if the subprocess sends more than self.limit
 # bytes. So just call self.read(self._limit) until EOF.
 blocks = []
 while True:
 block = await self.read(self._limit)
 if not block:
 break
 blocks.append(block)
 return b''.join(blocks)

 if not self._buffer and not self._eof:
 await self._wait_for_data('read')

 # This will work right even if buffer is less than n bytes
 data = bytes(self._buffer[:n])
 del self._buffer[:n]

 self._maybe_resume_transport()
 return data

 async def readexactly(self, n):
 """Read exactly `n` bytes.

 Raise an IncompleteReadError if EOF is reached before `n` bytes can be
 read. The IncompleteReadError.partial attribute of the exception will
 contain the partial read bytes.

 if n is zero, return empty bytes object.

 Returned value is not limited with limit, configured at stream
 creation.

 If stream was paused, this function will automatically resume it if
 needed.
 """
 if n < 0:
 raise ValueError('readexactly size can not be less than zero')

 if self._exception is not None:
 raise self._exception

 if n == 0:
 return b''

 while len(self._buffer) < n:
 if self._eof:
 incomplete = bytes(self._buffer)
 self._buffer.clear()
 raise IncompleteReadError(incomplete, n)

 await self._wait_for_data('readexactly')

 if len(self._buffer) == n:
 data = bytes(self._buffer)
 self._buffer.clear()
 else:
 data = bytes(self._buffer[:n])
 del self._buffer[:n]
 self._maybe_resume_transport()
 return data

 def __aiter__(self):
 return self

 async def __anext__(self):
 val = await self.readline()
 if val == b'':
 raise StopAsyncIteration
 return val