# wireprotov2peer.py - client side code for wire protocol version 2

#

# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import threading

from .i18n import _

from . import (

    encoding,

    error,

    pycompat,

    sslutil,

    url as urlmod,

    util,

    wireprotoframing,

    wireprototypes,

)

from .utils import cborutil

def formatrichmessage(atoms):

    """Format an encoded message from the framing protocol."""

    chunks = []

    for atom in atoms:

        msg = _(atom[b'msg'])

        if b'args' in atom:

            msg = msg % tuple(atom[b'args'])

        chunks.append(msg)

    return b''.join(chunks)

SUPPORTED_REDIRECT_PROTOCOLS = {

    b'http',

    b'https',

}

SUPPORTED_CONTENT_HASHES = {

    b'sha1',

    b'sha256',

}

def redirecttargetsupported(ui, target):

    """Determine whether a redirect target entry is supported.

    ``target`` should come from the capabilities data structure emitted by

    the server.

    """

    if target.get(b'protocol') not in SUPPORTED_REDIRECT_PROTOCOLS:

        ui.note(

            _(b'(remote redirect target %s uses unsupported protocol: %s)\n')

            % (target[b'name'], target.get(b'protocol', b''))

        )

        return False

    if target.get(b'snirequired') and not sslutil.hassni:

        ui.note(

            _(b'(redirect target %s requires SNI, which is unsupported)\n')

            % target[b'name']

        )

        return False

    if b'tlsversions' in target:

        tlsversions = set(target[b'tlsversions'])

        supported = set()

        for v in sslutil.supportedprotocols:

            assert v.startswith(b'tls')

            supported.add(v[3:])

        if not tlsversions & supported:

            ui.note(

                _(

                    b'(remote redirect target %s requires unsupported TLS '

                    b'versions: %s)\n'

                )

                % (target[b'name'], b', '.join(sorted(tlsversions)))

            )

            return False

    ui.note(_(b'(remote redirect target %s is compatible)\n') % target[b'name'])

    return True

def supportedredirects(ui, apidescriptor):

    """Resolve the "redirect" command request key given an API descriptor.

    Given an API descriptor returned by the server, returns a data structure

    that can be used in hte "redirect" field of command requests to advertise

    support for compatible redirect targets.

    Returns None if no redirect targets are remotely advertised or if none are

    supported.

    """

    if not apidescriptor or b'redirect' not in apidescriptor:

        return None

    targets = [

        t[b'name']

        for t in apidescriptor[b'redirect'][b'targets']

        if redirecttargetsupported(ui, t)

    ]

    hashes = [

        h

        for h in apidescriptor[b'redirect'][b'hashes']

        if h in SUPPORTED_CONTENT_HASHES

    ]

    return {

        b'targets': targets,

        b'hashes': hashes,

    }

class commandresponse(object):

    """Represents the response to a command request.

    Instances track the state of the command and hold its results.

    An external entity is required to update the state of the object when

    events occur.

    """

    def __init__(self, requestid, command, fromredirect=False):

        self.requestid = requestid

        self.command = command

        self.fromredirect = fromredirect

        # Whether all remote input related to this command has been

        # received.

        self._inputcomplete = False

        # We have a lock that is acquired when important object state is

        # mutated. This is to prevent race conditions between 1 thread

        # sending us new data and another consuming it.

        self._lock = threading.RLock()

        # An event is set when state of the object changes. This event

        # is waited on by the generator emitting objects.

        self._serviceable = threading.Event()

        self._pendingevents = []

        self._pendingerror = None

        self._decoder = cborutil.bufferingdecoder()

        self._seeninitial = False

        self._redirect = None

    def _oninputcomplete(self):

        with self._lock:

            self._inputcomplete = True

            self._serviceable.set()

    def _onresponsedata(self, data):

        available, readcount, wanted = self._decoder.decode(data)

        if not available:

            return

        with self._lock:

            for o in self._decoder.getavailable():

                if not self._seeninitial and not self.fromredirect:

                    self._handleinitial(o)

                    continue

                # We should never see an object after a content redirect,

                # as the spec says the main status object containing the

                # content redirect is the only object in the stream. Fail

                # if we see a misbehaving server.

                if self._redirect:

                    raise error.Abort(

                        _(

                            b'received unexpected response data '

                            b'after content redirect; the remote is '

                            b'buggy'

                        )

                    )

                self._pendingevents.append(o)

            self._serviceable.set()

    def _onerror(self, e):

        self._pendingerror = e

        with self._lock:

            self._serviceable.set()

    def _handleinitial(self, o):

        self._seeninitial = True

        if o[b'status'] == b'ok':

            return

        elif o[b'status'] == b'redirect':

            l = o[b'location']

            self._redirect = wireprototypes.alternatelocationresponse(

                url=l[b'url'],

                mediatype=l[b'mediatype'],

                size=l.get(b'size'),

                fullhashes=l.get(b'fullhashes'),

                fullhashseed=l.get(b'fullhashseed'),

                serverdercerts=l.get(b'serverdercerts'),

                servercadercerts=l.get(b'servercadercerts'),

            )

            return

        atoms = [{b'msg': o[b'error'][b'message']}]

        if b'args' in o[b'error']:

            atoms[0][b'args'] = o[b'error'][b'args']

        raise error.RepoError(formatrichmessage(atoms))

    def objects(self):

        """Obtained decoded objects from this response.

        This is a generator of data structures that were decoded from the

        command response.

        Obtaining the next member of the generator may block due to waiting

        on external data to become available.

        If the server encountered an error in the middle of serving the data

        or if another error occurred, an exception may be raised when

        advancing the generator.

        """

        while True:

            # TODO this can infinite loop if self._inputcomplete is never

            # set. We likely want to tie the lifetime of this object/state

            # to that of the background thread receiving frames and updating

            # our state.

            self._serviceable.wait(1.0)

            if self._pendingerror:

                raise self._pendingerror

            with self._lock:

                self._serviceable.clear()

                # Make copies because objects could be mutated during

                # iteration.

                stop = self._inputcomplete

                pending = list(self._pendingevents)

                self._pendingevents[:] = []

            for o in pending:

                yield o

            if stop:

                break

class clienthandler(object):

    """Object to handle higher-level client activities.

    The ``clientreactor`` is used to hold low-level state about the frame-based

    protocol, such as which requests and streams are active. This type is used

    for higher-level operations, such as reading frames from a socket, exposing

    and managing a higher-level primitive for representing command responses,

    etc. This class is what peers should probably use to bridge wire activity

    with the higher-level peer API.

    """

    def __init__(

        self, ui, clientreactor, opener=None, requestbuilder=util.urlreq.request

    ):

        self._ui = ui

        self._reactor = clientreactor

        self._requests = {}

        self._futures = {}

        self._responses = {}

        self._redirects = []

        self._frameseof = False

        self._opener = opener or urlmod.opener(ui)

        self._requestbuilder = requestbuilder

    def callcommand(self, command, args, f, redirect=None):

        """Register a request to call a command.

        Returns an iterable of frames that should be sent over the wire.

        """

        request, action, meta = self._reactor.callcommand(

            command, args, redirect=redirect

        )

        if action != b'noop':

            raise error.ProgrammingError(b'%s not yet supported' % action)

        rid = request.requestid

        self._requests[rid] = request

        self._futures[rid] = f

        # TODO we need some kind of lifetime on response instances otherwise

        # objects() may deadlock.

        self._responses[rid] = commandresponse(rid, command)

        return iter(())

    def flushcommands(self):

        """Flush all queued commands.

        Returns an iterable of frames that should be sent over the wire.

        """

        action, meta = self._reactor.flushcommands()

        if action != b'sendframes':

            raise error.ProgrammingError(b'%s not yet supported' % action)

        return meta[b'framegen']

    def readdata(self, framefh):

        """Attempt to read data and do work.

        Returns None if no data was read. Presumably this means we're

        done with all read I/O.

        """

        if not self._frameseof:

            frame = wireprotoframing.readframe(framefh)

            if frame is None:

                # TODO tell reactor?

                self._frameseof = True

            else:

                self._ui.debug(b'received %r\n' % frame)

                self._processframe(frame)

        # Also try to read the first redirect.

        if self._redirects:

            if not self._processredirect(*self._redirects[0]):

                self._redirects.pop(0)

        if self._frameseof and not self._redirects:

            return None

        return True

    def _processframe(self, frame):

        """Process a single read frame."""

        action, meta = self._reactor.onframerecv(frame)

        if action == b'error':

            e = error.RepoError(meta[b'message'])

            if frame.requestid in self._responses:

                self._responses[frame.requestid]._oninputcomplete()

            if frame.requestid in self._futures:

                self._futures[frame.requestid].set_exception(e)

                del self._futures[frame.requestid]

            else:

                raise e

            return

        elif action == b'noop':

            return

        elif action == b'responsedata':

            # Handled below.

            pass

        else:

            raise error.ProgrammingError(b'action not handled: %s' % action)

        if frame.requestid not in self._requests:

            raise error.ProgrammingError(

                b'received frame for unknown request; this is either a bug in '

                b'the clientreactor not screening for this or this instance was '

                b'never told about this request: %r' % frame

            )

        response = self._responses[frame.requestid]

        if action == b'responsedata':

            # Any failures processing this frame should bubble up to the

            # future tracking the request.

            try:

                self._processresponsedata(frame, meta, response)

            except BaseException as e:

                # If an exception occurs before the future is resolved,

                # fail the future. Otherwise, we stuff the exception on

                # the response object so it can be raised during objects()

                # iteration. If nothing is consuming objects(), we could

                # silently swallow this exception. That's a risk we'll have to

                # take.

                if frame.requestid in self._futures:

                    self._futures[frame.requestid].set_exception(e)

                    del self._futures[frame.requestid]

                    response._oninputcomplete()

                else:

                    response._onerror(e)

        else:

            raise error.ProgrammingError(

                b'unhandled action from clientreactor: %s' % action

            )