libervia-backend/libervia/backend/tools/common/dynamic_import.py

#!/usr/bin/env python3

# Libervia: an XMPP client
# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""tools dynamic import"""

from importlib import import_module
from types import ModuleType
from typing import Any, Literal

from libervia.backend.core import exceptions
from libervia.backend.core.log import getLogger
from libervia.backend.tools.config import (
    BridgeSettings,
    DBusBridgeSettings,
    PbBridgeSettings,
    Settings,
)

log = getLogger(__name__)

module_path = "libervia.frontends.bridge"


def import_bridge(name: str) -> ModuleType | None:
    """import bridge module

    @param name: name of the bridge to import (e.g.: dbus)
    @return: imported module or None if nothing is found
    """
    try:
        bridge_module = import_module(module_path + "." + name)
    except ImportError:
        try:
            bridge_module = import_module(module_path + "." + name + "_bridge")
        except ImportError as e:
            log.warning(f"Can't import bridge {name!r}: {e}")
            bridge_module = None
    return bridge_module


def _load_bridge(bridge_settings: BridgeSettings, verbose: bool = True):
    """Load requested bridge.

    @raise BridgeInitError: Bridge can't be initialised.
    """
    bridge_name: str = bridge_settings.type
    bridge_module = import_bridge(bridge_name)
    if bridge_module is None:
        log.error(f"Can't find bridge module of name {bridge_name}")
        raise exceptions.BridgeInitError
    if verbose:
        log.info(f"using {bridge_name} bridge")

    # FIXME: temporary class selection, bridges need to be refactored to always use async
    #   classes (and to not use a class starting with a lower case)
    try:
        bridge_cls = bridge_module.AIOBridge
    except AttributeError:
        bridge_cls = bridge_module.bridge
    try:
        return bridge_cls()
    except exceptions.BridgeInitError as e:
        raise e
    except Exception as e:
        log.exception(f"Can't load bridge {bridge_name}")
        raise exceptions.BridgeInitError from e


def load_bridge(config: Settings, verbose: bool = True) -> tuple[Any, BridgeSettings]:
    """Load and initialise the bridge.

    "auto" bridge is handled

    @param config: Libervia Settings
    @param is_backend: Set to True if calling from backend.
    @return: initialised bridge and bridge settings
    @raise BridgeInitError: Can't initialise this bridge.
    """
    bridges = config.bridges
    # FIXME: We only handle first bridge for now.
    bridge_settings = next(iter(bridges))
    bridge = None
    if bridge_settings.type == "auto":
        try:
            bridge_settings = DBusBridgeSettings()
            config.bridges = [bridge_settings]
            bridge = _load_bridge(bridge_settings, verbose=verbose)
        except exceptions.BridgeInitError as e:
            if verbose:
                log.warning(f"Can't load D-Bus bridge: {e}")
                log.info("Falling back to PB bridge.")
            bridge_settings = PbBridgeSettings()
            config.bridges = [bridge_settings]

    if bridge is None:
        bridge = _load_bridge(bridge_settings, verbose=verbose)

    return bridge, bridge_settings


async def _load_and_init_bridge(
    bridge_settings: BridgeSettings, verbose: bool, is_backend: bool
):
    """Load and set requested bridge.

    @raise BridgeInitError: Bridge can't be initialised.
    @raise BridgeExceptionNoService: Bridge is initialised, but the backend can't be
        found.
    """
    bridge = _load_bridge(bridge_settings, verbose)
    try:
        bridge_post_init = bridge.post_init
    except AttributeError:
        pass
    else:
        try:
            await bridge_post_init()
        except Exception as e:
            if verbose:
                log.warning(f"Could not initialize bridge: {e}")
            raise exceptions.BridgeInitError from e
    if not is_backend:
        # For frontends, we connect the bridge.
        try:
            await bridge.bridge_connect()
        except (exceptions.BridgeInitError, exceptions.BridgeExceptionNoService) as e:
            raise e
        except Exception as e:
            raise exceptions.BridgeInitError from e
    return bridge


async def load_and_init_bridge(
    config: Settings, verbose: bool = True, is_backend=False
) -> tuple[Any, BridgeSettings]:
    """Load and initialise the bridge.

    "auto" bridge is handled

    @param config: Libervia Settings
    @param is_backend: Set to True if calling from backend.
    @return: initialised bridge and bridge settings
    @raise BridgeInitError: Bridge can't be initialised.
    @raise BridgeExceptionNoService: Bridge is initialised, but the backend can't be
        found.
    """

    if is_backend:
        global module_path
        module_path = "libervia.backend.bridge"

    bridges = config.bridges
    # FIXME: We only handle first bridge for now.
    bridge_settings = next(iter(bridges))
    bridge = None
    if bridge_settings.type == "auto":
        try:
            bridge_settings = DBusBridgeSettings()
            config.bridges = [bridge_settings]
            bridge = await _load_and_init_bridge(bridge_settings, verbose, is_backend)
        except exceptions.BridgeInitError as e:
            if verbose:
                log.warning(f"Can't load D-Bus bridge: {e}")
                log.info("Falling back to PB bridge.")
            bridge_settings = PbBridgeSettings()
            config.bridges = [bridge_settings]

    if bridge is None:
        bridge = await _load_and_init_bridge(bridge_settings, verbose, is_backend)

    return bridge, bridge_settings