# Source code for asyncssh.stream

    # Copyright (c) 2013-2020 by Ron Frederick <ronf@timeheart.net> and others.
    #
    # This program and the accompanying materials are made available under
    # the terms of the Eclipse Public License v2.0 which accompanies this
    # distribution and is available at:
    #
    #     http://www.eclipse.org/legal/epl-2.0/
    #
    # This program may also be made available under the following secondary
    # licenses when the conditions for such availability set forth in the
    # Eclipse Public License v2.0 are satisfied:
    #
    #    GNU General Public License, Version 2.0, or any later versions of
    #    that license
    #
    # SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
    #
    # Contributors:
    #     Ron Frederick - initial implementation, API, and documentation

    """SSH stream handlers"""

    import asyncio
    import inspect
    import re

    from .constants import EXTENDED_DATA_STDERR
    from .misc import BreakReceived, SignalReceived
    from .misc import SoftEOFReceived, TerminalSizeChanged
    from .session import SSHClientSession, SSHServerSession
    from .session import SSHTCPSession, SSHUNIXSession
    from .sftp import run_sftp_server
    from .scp import run_scp_server

    _NEWLINE = object()

    class SSHReader:
        """SSH read stream handler"""

        def __init__(self, session, chan, datatype=None):
            self._session = session
            self._chan = chan
            self._datatype = datatype

        async def __aiter__(self):
            """Allow SSHReader to be an async iterator"""

            while not self.at_eof():
                yield await self.readline()

        @property
        def channel(self):
            """The SSH channel associated with this stream"""

            return self._chan

        @property
        def logger(self):
            """The SSH logger associated with this stream"""

            return self._chan.logger

        def get_extra_info(self, name, default=None):
            """Return additional information about this stream

               This method returns extra information about the channel
               associated with this stream. See :meth:`get_extra_info()
               <SSHClientChannel.get_extra_info>` on :class:`SSHClientChannel`
               for additional information.

            """

            return self._chan.get_extra_info(name, default)

        def feed_data(self, data):
            """Feed data to the associated session

               This method feeds data to the SSH session associated with
               this stream, providing compatibility with the
               :meth:`feed_data() <asyncio.StreamReader.feed_data>` method
               on :class:`asyncio.StreamReader`. This is mostly useful
               for testing.

            """

            self._session.data_received(data, self._datatype)

        def feed_eof(self):
            """Feed EOF to the associated session

               This method feeds an end-of-file indication to the SSH session
               associated with this stream, providing compatibility with the
               :meth:`feed_eof() <asyncio.StreamReader.feed_data>` method
               on :class:`asyncio.StreamReader`. This is mostly useful
               for testing.

            """

            self._session.eof_received()

        async def read(self, n=-1):
            """Read data from the stream

               This method is a coroutine which reads up to `n` bytes
               or characters from the stream. If `n` is not provided or
               set to `-1`, it reads until EOF or a signal is received.

               If EOF is received and the receive buffer is empty, an
               empty `bytes` or `str` object is returned.

               If the next data in the stream is a signal, the signal is
               delivered as a raised exception.

               .. note:: Unlike traditional `asyncio` stream readers,
                         the data will be delivered as either `bytes` or
                         a `str` depending on whether an encoding was
                         specified when the underlying channel was opened.

            """

            return await self._session.read(n, self._datatype, exact=False)

        async def readline(self):
            """Read one line from the stream

               This method is a coroutine which reads one line, ending in
               `'\\n'`.

               If EOF is received before `'\\n'` is found, the partial
               line is returned. If EOF is received and the receive buffer
               is empty, an empty `bytes` or `str` object is returned.

               If the next data in the stream is a signal, the signal is
               delivered as a raised exception.

               .. note:: In Python 3.5 and later, :class:`SSHReader` objects
                         can also be used as async iterators, returning input
                         data one line at a time.

            """

            try:
                return await self.readuntil(_NEWLINE)
            except asyncio.IncompleteReadError as exc:
                return exc.partial

        async def readuntil(self, separator):
            """Read data from the stream until `separator` is seen

               This method is a coroutine which reads from the stream until
               the requested separator is seen. If a match is found, the
               returned data will include the separator at the end.

               The separator argument can be either a single `bytes` or
               `str` value or a sequence of multiple values to match
               against, returning data as soon as any of the separators
               are found in the stream.

               If EOF or a signal is received before a match occurs, an
               :exc:`IncompleteReadError <asyncio.IncompleteReadError>`
               is raised and its `partial` attribute will contain the
               data in the stream prior to the EOF or signal.

               If the next data in the stream is a signal, the signal is
               delivered as a raised exception.

            """

            return await self._session.readuntil(separator, self._datatype)

        async def readexactly(self, n):
            """Read an exact amount of data from the stream

               This method is a coroutine which reads exactly n bytes or
               characters from the stream.

               If EOF or a signal is received in the stream before `n`
               bytes are read, an :exc:`IncompleteReadError
               <asyncio.IncompleteReadError>` is raised and its `partial`
               attribute will contain the data before the EOF or signal.

               If the next data in the stream is a signal, the signal is
               delivered as a raised exception.

            """

            return await self._session.read(n, self._datatype, exact=True)

        def at_eof(self):
            """Return whether the stream is at EOF

               This method returns `True` when EOF has been received and
               all data in the stream has been read.

            """

            return self._session.at_eof(self._datatype)

        def get_redirect_info(self):
            """Get information needed to redirect from this SSHReader"""

            return self._session, self._datatype

    class SSHWriter:
        """SSH write stream handler"""

        def __init__(self, session, chan, datatype=None):
            self._session = session
            self._chan = chan
            self._datatype = datatype

        @property
        def channel(self):
            """The SSH channel associated with this stream"""

            return self._chan

        @property
        def logger(self):
            """The SSH logger associated with this stream"""

            return self._chan.logger

        def get_extra_info(self, name, default=None):
            """Return additional information about this stream

               This method returns extra information about the channel
               associated with this stream. See :meth:`get_extra_info()
               <SSHClientChannel.get_extra_info>` on :class:`SSHClientChannel`
               for additional information.

            """

            return self._chan.get_extra_info(name, default)

        def can_write_eof(self):
            """Return whether the stream supports :meth:`write_eof`"""

            return self._chan.can_write_eof()

        def close(self):
            """Close the channel

               .. note:: After this is called, no data can be read or written
                         from any of the streams associated with this channel.

            """

            return self._chan.close()

        def is_closing(self):
            """Return if the stream is closing or is closed"""

            return self._chan.is_closing()

        async def wait_closed(self):
            """Wait until the stream is closed

               This should be called after :meth:`close` to wait until
               the underlying connection is closed.

            """

            await self._chan.wait_closed()

        async def drain(self):
            """Wait until the write buffer on the channel is flushed

               This method is a coroutine which blocks the caller if the
               stream is currently paused for writing, returning when
               enough data has been sent on the channel to allow writing
               to resume. This can be used to avoid buffering an excessive
               amount of data in the channel's send buffer.

            """

            return await self._session.drain(self._datatype)

        def write(self, data):
            """Write data to the stream

               This method writes bytes or characters to the stream.

               .. note:: Unlike traditional `asyncio` stream writers,
                         the data must be supplied as either `bytes` or
                         a `str` depending on whether an encoding was
                         specified when the underlying channel was opened.

            """

            return self._chan.write(data, self._datatype)

        def writelines(self, list_of_data):
            """Write a collection of data to the stream"""

            return self._chan.writelines(list_of_data, self._datatype)

        def write_eof(self):
            """Write EOF on the channel

               This method sends an end-of-file indication on the channel,
               after which no more data can be written.

               .. note:: On an :class:`SSHServerChannel` where multiple
                         output streams are created, writing EOF on one
                         stream signals EOF for all of them, since it
                         applies to the channel as a whole.

            """

            return self._chan.write_eof()

        def get_redirect_info(self):
            """Get information needed to redirect to this SSHWriter"""

            return self._session, self._datatype

    class SSHStreamSession:
        """SSH stream session handler"""

        def __init__(self):
            self._chan = None
            self._conn = None
            self._encoding = None
            self._errors = 'strict'
            self._loop = None
            self._limit = None
            self._exception = None
            self._eof_received = False
            self._connection_lost = False
            self._recv_buf = {None: []}
            self._recv_buf_len = 0
            self._read_locks = {None: asyncio.Lock()}
            self._read_waiters = {None: None}
            self._read_paused = False
            self._write_paused = False
            self._drain_waiters = {None: set()}

        async def _block_read(self, datatype):
            """Wait for more data to arrive on the stream"""

            try:
                waiter = self._loop.create_future()
                self._read_waiters[datatype] = waiter
                await waiter
            finally:
                self._read_waiters[datatype] = None

        def _unblock_read(self, datatype):
            """Signal that more data has arrived on the stream"""

            waiter = self._read_waiters[datatype]
            if waiter and not waiter.done():
                waiter.set_result(None)

        def _should_block_drain(self, _datatype):
            """Return whether output is still being written to the channel"""

            return self._write_paused and not self._connection_lost

        def _unblock_drain(self, datatype):
            """Signal that more data can be written on the stream"""

            if not self._should_block_drain(datatype):
                for waiter in self._drain_waiters[datatype]:
                    if not waiter.done(): # pragma: no branch
                        waiter.set_result(None)

        def _should_pause_reading(self):
            """Return whether to pause reading from the channel"""

            return self._limit and self._recv_buf_len >= self._limit

        def _maybe_pause_reading(self):
            """Pause reading if necessary"""

            if not self._read_paused and self._should_pause_reading():
                self._read_paused = True
                self._chan.pause_reading()
                return True
            else:
                return False

        def _maybe_resume_reading(self):
            """Resume reading if necessary"""

            if self._read_paused and not self._should_pause_reading():
                self._read_paused = False
                self._chan.resume_reading()
                return True
            else:
                return False

        def connection_made(self, chan):
            """Handle a newly opened channel"""

            self._chan = chan
            self._conn = chan.get_connection()
            self._encoding, self._errors = chan.get_encoding()
            self._loop = chan.get_loop()
            self._limit = self._chan.get_recv_window()

            for datatype in chan.get_read_datatypes():
                self._recv_buf[datatype] = []
                self._read_locks[datatype] = asyncio.Lock()
                self._read_waiters[datatype] = None

            for datatype in chan.get_write_datatypes():
                self._drain_waiters[datatype] = set()

        def connection_lost(self, exc):
            """Handle an incoming channel close"""

            self._connection_lost = True
            self._exception = exc

            if not self._eof_received:
                if exc:
                    for datatype in self._read_waiters:
                        self._recv_buf[datatype].append(exc)

                self.eof_received()

            for datatype in self._drain_waiters:
                self._unblock_drain(datatype)

        def data_received(self, data, datatype):
            """Handle incoming data on the channel"""

            self._recv_buf[datatype].append(data)
            self._recv_buf_len += len(data)
            self._unblock_read(datatype)
            self._maybe_pause_reading()

        def eof_received(self):
            """Handle an incoming end of file on the channel"""

            self._eof_received = True

            for datatype in self._read_waiters:
                self._unblock_read(datatype)

            return True

        def at_eof(self, datatype):
            """Return whether end of file has been received on the channel"""

            return self._eof_received and not self._recv_buf[datatype]

        def pause_writing(self):
            """Handle a request to pause writing on the channel"""

            self._write_paused = True

        def resume_writing(self):
            """Handle a request to resume writing on the channel"""

            self._write_paused = False

            for datatype in self._drain_waiters:
                self._unblock_drain(datatype)

        async def read(self, n, datatype, exact):
            """Read data from the channel"""

            recv_buf = self._recv_buf[datatype]
            buf = '' if self._encoding else b''
            data = []

            async with self._read_locks[datatype]:
                while True:
                    while recv_buf and n != 0:
                        if isinstance(recv_buf[0], Exception):
                            if data:
                                break
                            else:
                                exc = recv_buf.pop(0)

                                if isinstance(exc, SoftEOFReceived):
                                    n = 0
                                    break
                                else:
                                    raise exc

                        l = len(recv_buf[0])
                        if l > n > 0:
                            data.append(recv_buf[0][:n])
                            recv_buf[0] = recv_buf[0][n:]
                            self._recv_buf_len -= n
                            n = 0
                            break

                        data.append(recv_buf.pop(0))
                        self._recv_buf_len -= l
                        n -= l

                    if self._maybe_resume_reading():
                        continue

                    if n == 0 or (n > 0 and data and not exact) or \
                            (n < 0 and recv_buf) or self._eof_received:
                        break

                    await self._block_read(datatype)

            buf = buf.join(data)
            if n > 0 and exact:
                raise asyncio.IncompleteReadError(buf, len(buf) + n)

            return buf

        async def readuntil(self, separator, datatype):
            """Read data from the channel until a separator is seen"""

            if separator is _NEWLINE:
                separator = '\n' if self._encoding else b'\n'
            elif not separator:
                raise ValueError('Separator cannot be empty')

            if isinstance(separator, (str, bytes)):
                separators = [separator]
            else:
                separators = list(separator)

            seplen = max(len(sep) for sep in separators)
            bar = '|' if self._encoding else b'|'
            pat = re.compile(bar.join(map(re.escape, separators)))
            recv_buf = self._recv_buf[datatype]
            buf = '' if self._encoding else b''
            curbuf = 0
            buflen = 0

            async with self._read_locks[datatype]:
                while True:
                    while curbuf < len(recv_buf):
                        if isinstance(recv_buf[curbuf], Exception):
                            if buf:
                                recv_buf[:curbuf] = []
                                self._recv_buf_len -= buflen
                                raise asyncio.IncompleteReadError(buf, None)
                            else:
                                exc = recv_buf.pop(0)

                                if isinstance(exc, SoftEOFReceived):
                                    return buf
                                else:
                                    raise exc

                        buf += recv_buf[curbuf]
                        start = max(buflen + 1 - seplen, 0)

                        match = pat.search(buf, start)
                        if match:
                            idx = match.end()
                            recv_buf[:curbuf] = []
                            recv_buf[0] = buf[idx:]
                            buf = buf[:idx]
                            self._recv_buf_len -= idx

                            if not recv_buf[0]:
                                recv_buf.pop(0)

                            self._maybe_resume_reading()
                            return buf

                        buflen += len(recv_buf[curbuf])
                        curbuf += 1

                    if self._read_paused or self._eof_received:
                        recv_buf[:curbuf] = []
                        self._recv_buf_len -= buflen
                        self._maybe_resume_reading()
                        raise asyncio.IncompleteReadError(buf, None)

                    await self._block_read(datatype)

        async def drain(self, datatype):
            """Wait for data written to the channel to drain"""

            while self._should_block_drain(datatype):
                try:
                    waiter = self._loop.create_future()
                    self._drain_waiters[datatype].add(waiter)
                    await waiter
                finally:
                    self._drain_waiters[datatype].remove(waiter)

            if self._connection_lost:
                exc = self._exception

                if not exc and self._write_paused:
                    exc = BrokenPipeError()

                if exc:
                    raise exc

    class SSHClientStreamSession(SSHStreamSession, SSHClientSession):
        """SSH client stream session handler"""

    class SSHServerStreamSession(SSHStreamSession, SSHServerSession):
        """SSH server stream session handler"""

        def __init__(self, session_factory, sftp_factory, allow_scp):
            super().__init__()

            self._session_factory = session_factory
            self._sftp_factory = sftp_factory
            self._allow_scp = allow_scp and bool(sftp_factory)

        def _init_sftp_server(self):
            """Initialize an SFTP server for this stream to use"""

            self._chan.set_encoding(None)
            self._encoding = None

            return self._sftp_factory(self._chan)

        def shell_requested(self):
            """Return whether a shell can be requested"""

            return bool(self._session_factory)

        def exec_requested(self, command):
            """Return whether execution of a command can be requested"""

            # Avoid incorrect pylint suggestion to use ternary
            # pylint: disable=consider-using-ternary

            return ((self._allow_scp and command.startswith('scp ')) or
                    bool(self._session_factory))

        def subsystem_requested(self, subsystem):
            """Return whether starting a subsystem can be requested"""

            if subsystem == 'sftp':
                return bool(self._sftp_factory)
            else:
                return bool(self._session_factory)

        def session_started(self):
            """Start a session for this newly opened server channel"""

            command = self._chan.get_command()

            stdin = SSHReader(self, self._chan)
            stdout = SSHWriter(self, self._chan)
            stderr = SSHWriter(self, self._chan, EXTENDED_DATA_STDERR)

            if self._chan.get_subsystem() == 'sftp':
                handler = run_sftp_server(self._init_sftp_server(), stdin, stdout)
            elif self._allow_scp and command and command.startswith('scp '):
                handler = run_scp_server(self._init_sftp_server(), command,
                                         stdin, stdout, stderr)
            else:
                handler = self._session_factory(stdin, stdout, stderr)

            if inspect.isawaitable(handler):
                self._conn.create_task(handler, stdin.logger)

        def break_received(self, msec):
            """Handle an incoming break on the channel"""

            self._recv_buf[None].append(BreakReceived(msec))
            self._unblock_read(None)
            return True

        def signal_received(self, signal):
            """Handle an incoming signal on the channel"""

            self._recv_buf[None].append(SignalReceived(signal))
            self._unblock_read(None)

        def soft_eof_received(self):
            """Handle an incoming soft EOF on the channel"""

            self._recv_buf[None].append(SoftEOFReceived())
            self._unblock_read(None)

        def terminal_size_changed(self, width, height, pixwidth, pixheight):
            """Handle an incoming terminal size change on the channel"""

            self._recv_buf[None].append(TerminalSizeChanged(width, height,
                                                            pixwidth, pixheight))
            self._unblock_read(None)

    class SSHSocketStreamSession(SSHStreamSession):
        """Socket stream session handler"""

        def __init__(self, handler_factory=None):
            super().__init__()

            self._handler_factory = handler_factory

        def session_started(self):
            """Start a session for this newly opened socket channel"""

            if self._handler_factory:
                reader = SSHReader(self, self._chan)
                writer = SSHWriter(self, self._chan)

                handler = self._handler_factory(reader, writer)

                if inspect.isawaitable(handler):
                    self._conn.create_task(handler, reader.logger)

    class SSHTCPStreamSession(SSHSocketStreamSession, SSHTCPSession):
        """TCP stream session handler"""

    class SSHUNIXStreamSession(SSHSocketStreamSession, SSHUNIXSession):
        """UNIX stream session handler"""