path: root/synapse/util/__init__.py

# Copyright 2014-2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import json
import logging
import re
import typing
from typing import Any, Callable, Dict, Generator, Pattern

import attr
from frozendict import frozendict

from twisted.internet import defer, task
from twisted.internet.defer import Deferred
from twisted.internet.interfaces import IDelayedCall, IReactorTime
from twisted.internet.task import LoopingCall
from twisted.python.failure import Failure

from synapse.logging import context

if typing.TYPE_CHECKING:
    pass

logger = logging.getLogger(__name__)


_WILDCARD_RUN = re.compile(r"([\?\*]+)")


def _reject_invalid_json(val: Any) -> None:
    """Do not allow Infinity, -Infinity, or NaN values in JSON."""
    raise ValueError("Invalid JSON value: '%s'" % val)


def _handle_frozendict(obj: Any) -> Dict[Any, Any]:
    """Helper for json_encoder. Makes frozendicts serializable by returning
    the underlying dict
    """
    if type(obj) is frozendict:
        # fishing the protected dict out of the object is a bit nasty,
        # but we don't really want the overhead of copying the dict.
        try:
            # Safety: we catch the AttributeError immediately below.
            # See https://github.com/matrix-org/python-canonicaljson/issues/36#issuecomment-927816293
            # for discussion on how frozendict's internals have changed over time.
            return obj._dict  # type: ignore[attr-defined]
        except AttributeError:
            # When the C implementation of frozendict is used,
            # there isn't a `_dict` attribute with a dict
            # so we resort to making a copy of the frozendict
            return dict(obj)
    raise TypeError(
        "Object of type %s is not JSON serializable" % obj.__class__.__name__
    )


# A custom JSON encoder which:
#   * handles frozendicts
#   * produces valid JSON (no NaNs etc)
#   * reduces redundant whitespace
json_encoder = json.JSONEncoder(
    allow_nan=False, separators=(",", ":"), default=_handle_frozendict
)

# Create a custom decoder to reject Python extensions to JSON.
json_decoder = json.JSONDecoder(parse_constant=_reject_invalid_json)


def unwrapFirstError(failure: Failure) -> Failure:
    # defer.gatherResults and DeferredLists wrap failures.
    failure.trap(defer.FirstError)
    return failure.value.subFailure  # type: ignore[union-attr]  # Issue in Twisted's annotations


@attr.s(slots=True)
class Clock:
    """
    A Clock wraps a Twisted reactor and provides utilities on top of it.

    Args:
        reactor: The Twisted reactor to use.
    """

    _reactor: IReactorTime = attr.ib()

    @defer.inlineCallbacks  # type: ignore[arg-type]  # Issue in Twisted's type annotations
    def sleep(self, seconds: float) -> "Generator[Deferred[float], Any, Any]":
        d: defer.Deferred[float] = defer.Deferred()
        with context.PreserveLoggingContext():
            self._reactor.callLater(seconds, d.callback, seconds)
            res = yield d
        return res

    def time(self) -> float:
        """Returns the current system time in seconds since epoch."""
        return self._reactor.seconds()

    def time_msec(self) -> int:
        """Returns the current system time in milliseconds since epoch."""
        return int(self.time() * 1000)

    def looping_call(self, f: Callable, msec: float, *args, **kwargs) -> LoopingCall:
        """Call a function repeatedly.

        Waits `msec` initially before calling `f` for the first time.

        Note that the function will be called with no logcontext, so if it is anything
        other than trivial, you probably want to wrap it in run_as_background_process.

        Args:
            f: The function to call repeatedly.
            msec: How long to wait between calls in milliseconds.
            *args: Postional arguments to pass to function.
            **kwargs: Key arguments to pass to function.
        """
        call = task.LoopingCall(f, *args, **kwargs)
        call.clock = self._reactor
        d = call.start(msec / 1000.0, now=False)
        d.addErrback(log_failure, "Looping call died", consumeErrors=False)
        return call

    def call_later(self, delay, callback, *args, **kwargs) -> IDelayedCall:
        """Call something later

        Note that the function will be called with no logcontext, so if it is anything
        other than trivial, you probably want to wrap it in run_as_background_process.

        Args:
            delay(float): How long to wait in seconds.
            callback(function): Function to call
            *args: Postional arguments to pass to function.
            **kwargs: Key arguments to pass to function.
        """

        def wrapped_callback(*args, **kwargs):
            with context.PreserveLoggingContext():
                callback(*args, **kwargs)

        with context.PreserveLoggingContext():
            return self._reactor.callLater(delay, wrapped_callback, *args, **kwargs)

    def cancel_call_later(self, timer: IDelayedCall, ignore_errs: bool = False) -> None:
        try:
            timer.cancel()
        except Exception:
            if not ignore_errs:
                raise


def log_failure(failure, msg, consumeErrors=True):
    """Creates a function suitable for passing to `Deferred.addErrback` that
    logs any failures that occur.

    Args:
        msg (str): Message to log
        consumeErrors (bool): If true consumes the failure, otherwise passes
            on down the callback chain

    Returns:
        func(Failure)
    """

    logger.error(
        msg, exc_info=(failure.type, failure.value, failure.getTracebackObject())
    )

    if not consumeErrors:
        return failure


def glob_to_regex(glob: str, word_boundary: bool = False) -> Pattern:
    """Converts a glob to a compiled regex object.

    Args:
        glob: pattern to match
        word_boundary: If True, the pattern will be allowed to match at word boundaries
           anywhere in the string. Otherwise, the pattern is anchored at the start and
           end of the string.

    Returns:
        compiled regex pattern
    """

    # Patterns with wildcards must be simplified to avoid performance cliffs
    # - The glob `?**?**?` is equivalent to the glob `???*`
    # - The glob `???*` is equivalent to the regex `.{3,}`
    chunks = []
    for chunk in _WILDCARD_RUN.split(glob):
        # No wildcards? re.escape()
        if not _WILDCARD_RUN.match(chunk):
            chunks.append(re.escape(chunk))
            continue

        # Wildcards? Simplify.
        qmarks = chunk.count("?")
        if "*" in chunk:
            chunks.append(".{%d,}" % qmarks)
        else:
            chunks.append(".{%d}" % qmarks)

    res = "".join(chunks)

    if word_boundary:
        res = re_word_boundary(res)
    else:
        # \A anchors at start of string, \Z at end of string
        res = r"\A" + res + r"\Z"

    return re.compile(res, re.IGNORECASE)


def re_word_boundary(r: str) -> str:
    """
    Adds word boundary characters to the start and end of an
    expression to require that the match occur as a whole word,
    but do so respecting the fact that strings starting or ending
    with non-word characters will change word boundaries.
    """
    # we can't use \b as it chokes on unicode. however \W seems to be okay
    # as shorthand for [^0-9A-Za-z_].
    return r"(^|\W)%s(\W|$)" % (r,)