# Copyright 2017-present Open Networking Foundation
#
# 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.

""" ModelAccessor

    A class for abstracting access to models. Used to get any djangoisms out
    of the synchronizer code base.

    This module will import all models into this module's global scope, so doing
    a "from modelaccessor import *" from a calling module ought to import all
    models into the calling module's scope.
"""

from __future__ import absolute_import

import functools
import importlib
import os
import signal
import sys
from threading import Timer

from xosconfig import Config
from xosutil.autodiscover_version import autodiscover_version_of_main

from .loadmodels import ModelLoadClient

from multistructlog import create_logger
log = create_logger(Config().get("logging"))

after_reactor_exit_code = None
orig_sigint = None
model_accessor = None


class ModelAccessor(object):
    def __init__(self):
        self.all_model_classes = self.get_all_model_classes()

    def __getattr__(self, name):
        """ Wrapper for getattr to facilitate retrieval of classes """
        has_model_class = self.__getattribute__("has_model_class")
        get_model_class = self.__getattribute__("get_model_class")
        if has_model_class(name):
            return get_model_class(name)

        # Default behaviour
        return self.__getattribute__(name)

    def get_all_model_classes(self):
        """ Build a dictionary of all model class names """
        raise Exception("Not Implemented")

    def get_model_class(self, name):
        """ Given a class name, return that model class """
        return self.all_model_classes[name]

    def has_model_class(self, name):
        """ Given a class name, return that model class """
        return name in self.all_model_classes

    def fetch_pending(self, main_objs, deletion=False):
        """ Execute the default fetch_pending query """
        raise Exception("Not Implemented")

    def fetch_policies(self, main_objs, deletion=False):
        """ Execute the default fetch_pending query """
        raise Exception("Not Implemented")

    def reset_queries(self):
        """ Reset any state between passes of synchronizer. For django, to
            limit memory consumption of cached queries.
        """
        pass

    def connection_close(self):
        """ Close any active database connection. For django, to limit memory
            consumption.
        """
        pass

    def check_db_connection_okay(self):
        """ Checks to make sure the db connection is okay """
        pass

    def obj_exists(self, o):
        """ Return True if the object exists in the data model """
        raise Exception("Not Implemented")

    def obj_in_list(self, o, olist):
        """ Return True if o is the same as one of the objects in olist """
        raise Exception("Not Implemented")

    def now(self):
        """ Return the current time for timestamping purposes """
        raise Exception("Not Implemented")

    def is_type(self, obj, name):
        """ returns True is obj is of model type "name" """
        raise Exception("Not Implemented")

    def is_instance(self, obj, name):
        """ returns True if obj is of model type "name" or is a descendant """
        raise Exception("Not Implemented")

    def get_content_type_id(self, obj):
        raise Exception("Not Implemented")

    def journal_object(self, o, operation, msg=None, timestamp=None):
        pass

    def create_obj(self, cls, **kwargs):
        raise Exception("Not Implemented")


def import_models_to_globals():
    # add all models to globals
    for (k, v) in model_accessor.all_model_classes.items():
        globals()[k] = v

    # xosbase doesn't exist from the synchronizer's perspective, so fake out
    # ModelLink.
    if "ModelLink" not in globals():

        class ModelLink:
            def __init__(self, dest, via, into=None):
                self.dest = dest
                self.via = via
                self.into = into

        globals()["ModelLink"] = ModelLink


def keep_trying(client, reactor):
    # Keep checking the connection to wait for it to become unavailable.
    # Then reconnect. The strategy is to send NoOp operations, one per second, until eventually a NoOp throws an
    # exception. This will indicate the server has reset. When that happens, we force the client to reconnect, and
    # it will download a new API from the server.

    from xosapi.xos_grpc_client import Empty

    try:
        client.utility.NoOp(Empty())
    except Exception as e:
        # If we caught an exception, then the API has become unavailable.
        # So reconnect.

        log.exception("exception in NoOp", e=e)
        log.info("restarting synchronizer")

        os.execv(sys.executable, ["python"] + sys.argv)
        return

    reactor.callLater(1, functools.partial(keep_trying, client, reactor))


def unload_models(client, reactor, version):
    # This function is called by a timer until it succeeds.
    log.info("unload_models initiated by timer")

    try:
        result = ModelLoadClient(client).unload_models(
            Config.get("name"),
            version=version,
            cleanup_behavior=ModelLoadClient.AUTOMATICALLY_CLEAN)

        log.debug("Unload response", result=result)

        if result.status in [result.SUCCESS, result.SUCCESS_NOTHING_CHANGED]:
            log.info("Models successfully unloaded. Exiting with status", code=0)
            sys.exit(0)

        if result.status == result.TRYAGAIN:
            log.info("TRYAGAIN received. Expect to try again in 30 seconds.")

    except Exception:
        # If the synchronizer is operational, then assume the ORM's restart_on_disconnect will deal with the
        # connection being lost.
        log.exception("Error while unloading. Expect to try again in 30 seconds.")

    Timer(30, functools.partial(unload_models, client, reactor, version)).start()


def exit_while_inside_reactor(reactor, code):
    """ Calling sys.exit() while inside reactor ends up trapped by reactor.

        So what we'll do is set a flag indicating we want to exit, then stop reactor, then return
    """
    global after_reactor_exit_code

    reactor.stop()
    signal.signal(signal.SIGINT, orig_sigint)
    after_reactor_exit_code = code


def grpcapi_reconnect(client, reactor):
    global model_accessor

    # Make sure to try to load models before trying to initialize the ORM. It might be the ORM is broken because it
    # is waiting on our models.

    if Config.get("models_dir"):
        version = autodiscover_version_of_main(max_parent_depth=0) or "unknown"
        log.info("Service version is %s" % version, core_version=Config.get("core_version"))
        try:
            if Config.get("desired_state") == "load":
                ModelLoadClient(client).upload_models(
                    Config.get("name"), Config.get("models_dir"), version=version
                )
            elif Config.get("desired_state") == "unload":
                # Try for an easy unload. If there's no dirty models, then unload will succeed without
                # requiring us to setup the synchronizer.
                log.info("Trying for an easy unload_models")
                result = ModelLoadClient(client).unload_models(
                    Config.get("name"),
                    version=version,
                    cleanup_behavior=1)  # FIXME: hardcoded value for automatic delete
                if result.status in [result.SUCCESS, result.SUCCESS_NOTHING_CHANGED]:
                    log.info("Models successfully unloaded. Synchronizer exiting")
                    exit_while_inside_reactor(reactor, 0)
                    return

                # We couldn't unload the easy way, so we'll have to do it the hard way. Fall through and
                # setup the synchronizer.
            else:
                log.error("Misconfigured", desired_state=Config.get("desired_state"))
                exit_while_inside_reactor(reactor, -1)
                return
        except Exception as e:  # TODO: narrow exception scope
            if (
                hasattr(e, "code")
                and callable(e.code)
                and hasattr(e.code(), "name")
                and (e.code().name) == "UNAVAILABLE"
            ):
                # We need to make sure we force a reconnection, as it's possible that we will end up downloading a
                # new xos API.
                log.info("grpc unavailable during loadmodels. Force a reconnect")
                client.connected = False
                client.connect()
                return

            elif (
                hasattr(e, "code")
                and callable(e.code)
                and hasattr(e.code(), "name")
                and (e.code().name) == "INVALID_ARGUMENT"
            ):
                # in this case there is a version mismatch between the service and the core,
                # shut down the process so it's clear something is wrong
                log.error(e.details())

                # kill the process so the operator is aware something is wrong
                log.info("shutting down")
                exit_while_inside_reactor(reactor, 1)
                return

            log.exception("failed to onboard models")
            # If it's some other error, then we don't need to force a reconnect. Just try the LoadModels() again.
            reactor.callLater(10, functools.partial(grpcapi_reconnect, client, reactor))
            return

    # If the ORM is broken, then wait for the orm to become available.

    if not getattr(client, "xos_orm", None):
        log.warning("No xos_orm. Will keep trying...")
        reactor.callLater(1, functools.partial(keep_trying, client, reactor))
        return

    # this will prevent updated timestamps from being automatically updated
    client.xos_orm.caller_kind = "synchronizer"

    client.xos_orm.restart_on_disconnect = True

    from .apiaccessor import CoreApiModelAccessor

    model_accessor = CoreApiModelAccessor(orm=client.xos_orm)

    # If required_models is set, then check to make sure the required_models
    # are present. If not, then the synchronizer needs to go to sleep until
    # the models show up.

    required_models = Config.get("required_models")
    if required_models:
        required_models = [x.strip() for x in required_models]

        missing = []
        found = []
        for model in required_models:
            if model_accessor.has_model_class(model):
                found.append(model)
            else:
                missing.append(model)

        log.info("required_models, found:", models=", ".join(found))
        if missing:
            log.warning("required_models: missing", models=", ".join(missing))
            # We're missing a required model. Give up and wait for the connection
            # to reconnect, and hope our missing model has shown up.
            reactor.callLater(1, functools.partial(keep_trying, client, reactor))
            return

    # import all models to global space
    import_models_to_globals()

    # Synchronizer framework isn't ready to embrace reactor yet...
    reactor.stop()

    # Restore the sigint handler
    signal.signal(signal.SIGINT, orig_sigint)

    # Check to see if we still want to unload
    if Config.get("desired_state") == "unload":
        Timer(30, functools.partial(unload_models, client, reactor, version)).start()


def config_accessor_grpcapi():
    global orig_sigint

    log.info("Connecting to the gRPC API")

    grpcapi_endpoint = Config.get("accessor.endpoint")
    grpcapi_username = Config.get("accessor.username")
    grpcapi_password = Config.get("accessor.password")

    # if password starts with "@", then retreive the password from a file
    if grpcapi_password.startswith("@"):
        fn = grpcapi_password[1:]
        if not os.path.exists(fn):
            raise Exception("%s does not exist" % fn)
        grpcapi_password = open(fn).readline().strip()

    from xosapi.xos_grpc_client import SecureClient
    from twisted.internet import reactor

    grpcapi_client = SecureClient(
        endpoint=grpcapi_endpoint, username=grpcapi_username, password=grpcapi_password
    )
    grpcapi_client.set_reconnect_callback(
        functools.partial(grpcapi_reconnect, grpcapi_client, reactor)
    )
    grpcapi_client.start()

    # Start reactor. This will cause the client to connect and then execute
    # grpcapi_callback().

    # Reactor will take over SIGINT during reactor.run(), but does not return it when reactor.stop() is called.

    orig_sigint = signal.getsignal(signal.SIGINT)

    # Start reactor. This will cause the client to connect and then execute
    # grpcapi_callback().

    reactor.run()

    # Catch if we wanted to stop while inside of a reactor callback
    if after_reactor_exit_code is not None:
        log.info("exiting with status", code=after_reactor_exit_code)
        sys.exit(after_reactor_exit_code)


def config_accessor_mock():
    global model_accessor

    # the mock model accessor always gets built to a temporary location
    if "/tmp/mock_modelaccessor" not in sys.path:
        sys.path.append("/tmp/mock_modelaccessor")

    from mock_modelaccessor import model_accessor as mock_model_accessor

    model_accessor = mock_model_accessor

    # mock_model_accessor doesn't have an all_model_classes field, so make one.
    import mock_modelaccessor as mma

    all_model_classes = {}
    for k in dir(mma):
        v = getattr(mma, k)
        if hasattr(v, "leaf_model_name"):
            all_model_classes[k] = v

    model_accessor.all_model_classes = all_model_classes

    import_models_to_globals()


def config_accessor():
    accessor_kind = Config.get("accessor.kind")

    if accessor_kind == "testframework":
        config_accessor_mock()
    elif accessor_kind == "grpcapi":
        config_accessor_grpcapi()
    else:
        raise Exception("Unknown accessor kind %s" % accessor_kind)

    # now import any wrappers that the synchronizer needs to add to the ORM
    if Config.get("wrappers"):
        for wrapper_name in Config.get("wrappers"):
            importlib.import_module(wrapper_name)


config_accessor()