# Copyright 2021-2023 H2020 TeraFlow (https://www.teraflow-h2020.eu/)
#
# 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 threading
from typing import Any, Iterator, List, Optional, Tuple, Union

# Special resource names to request to the driver to retrieve the specified configuration/structural resources.
# These resource names should be used with GetConfig() method.
RESOURCE_ENDPOINTS         = '__endpoints__'
RESOURCE_INTERFACES        = '__interfaces__'
RESOURCE_NETWORK_INSTANCES = '__network_instances__'
RESOURCE_ROUTING_POLICIES  = '__routing_policies__'

class _Driver:
    def __init__(self, address : str, port : int, **settings) -> None:
        """ Initialize Driver.
            Parameters:
                address : str
                    The address of the device
                port : int
                    The port of the device
                **settings
                    Extra settings required by the driver.
        """
        raise NotImplementedError()

    def Connect(self) -> bool:
        """ Connect to the Device.
            Returns:
                succeeded : bool
                    Boolean variable indicating if connection succeeded.
        """
        raise NotImplementedError()

    def Disconnect(self) -> bool:
        """ Disconnect from the Device.
            Returns:
                succeeded : bool
                    Boolean variable indicating if disconnection succeeded.
        """
        raise NotImplementedError()

    def GetInitialConfig(self) -> List[Tuple[str, Any]]:
        """ Retrieve initial configuration of entire device.
            Returns:
                values : List[Tuple[str, Any]]
                    List of tuples (resource key, resource value) for resource keys.
        """
        raise NotImplementedError()

    def GetConfig(self, resource_keys : List[str] = []) -> List[Tuple[str, Union[Any, None, Exception]]]:
        """ Retrieve running configuration of entire device, or selected resource keys.
            Parameters:
                resource_keys : List[str]
                    List of keys pointing to the resources to be retrieved.
            Returns:
                values : List[Tuple[str, Union[Any, None, Exception]]]
                    List of tuples (resource key, resource value) for resource keys requested. If a resource is found,
                    the appropriate value type must be retrieved. If a resource is not found, None must be retrieved as
                    value for that resource. In case of Exception, the Exception must be retrieved as value.
        """
        raise NotImplementedError()

    def SetConfig(self, resources : List[Tuple[str, Any]]) -> List[Union[bool, Exception]]:
        """ Create/Update configuration for a list of resources.
            Parameters:
                resources : List[Tuple[str, Any]]
                    List of tuples, each containing a resource_key pointing the resource to be modified, and a
                    resource_value containing the new value to be set.
            Returns:
                results : List[Union[bool, Exception]]
                    List of results for resource key changes requested. Return values must be in the same order than
                    resource keys requested. If a resource is properly set, True must be retrieved; otherwise, the
                    Exception that is raised during the processing must be retrieved.
        """
        raise NotImplementedError()

    def DeleteConfig(self, resources : List[Tuple[str, Any]]) -> List[Union[bool, Exception]]:
        """ Delete configuration for a list of resources.
            Parameters:
                resources : List[Tuple[str, Any]]
                    List of tuples, each containing a resource_key pointing the resource to be modified, and a
                    resource_value containing possible additionally required values to locate the value to be removed.
            Returns:
                results : List[bool]
                    List of results for resource key deletions requested. Return values must be in the same order than
                    resource keys requested. If a resource is properly deleted, True must be retrieved; otherwise, the
                    Exception that is raised during the processing must be retrieved.
        """
        raise NotImplementedError()

    def SubscribeState(self, subscriptions : List[Tuple[str, float, float]]) -> List[Union[bool, Exception]]:
        """ Subscribe to state information of entire device, or selected resources. Subscriptions are incremental.
            Driver should keep track of requested resources.
            Parameters:
                subscriptions : List[Tuple[str, float, float]]
                    List of tuples, each containing a resource_key pointing the resource to be subscribed, a
                    sampling_duration, and a sampling_interval (both in seconds with float representation) defining,
                    respectively, for how long monitoring should last, and the desired monitoring interval for the
                    resource specified.
            Returns:
                results : List[bool]
                    List of results for resource key subscriptions requested. Return values must be in the same order
                    than resource keys requested. If a resource is properly subscribed, True must be retrieved;
                    otherwise, the Exception that is raised during the processing must be retrieved.
        """
        raise NotImplementedError()

    def UnsubscribeState(self, subscriptions : List[Tuple[str, float, float]]) -> List[Union[bool, Exception]]:
        """ Unsubscribe from state information of entire device, or selected resources. Subscriptions are incremental.
            Driver should keep track of requested resources.
            Parameters:
                subscriptions : List[str]
                    List of tuples, each containing a resource_key pointing the resource to be subscribed, a
                    sampling_duration, and a sampling_interval (both in seconds with float representation) defining,
                    respectively, for how long monitoring should last, and the desired monitoring interval for the
                    resource specified.
            Returns:
                results : List[Union[bool, Exception]]
                    List of results for resource key unsubscriptions requested. Return values must be in the same order
                    than resource keys requested. If a resource is properly unsubscribed, True must be retrieved;
                    otherwise, the Exception that is raised during the processing must be retrieved.
        """
        raise NotImplementedError()

    def GetState(
        self, blocking=False, terminate : Optional[threading.Event] = None
    ) -> Iterator[Tuple[float, str, Any]]:
        """ Retrieve last collected values for subscribed resources. Operates as a generator, so this method should be
            called once and will block until values are available. When values are available, it should yield each of
            them and block again until new values are available. When the driver is destroyed, GetState() can return
            instead of yield to terminate the loop. Terminate enables to request interruption of the generation.
            Examples:
                # keep looping waiting for extra samples (generator loop)
                terminate = threading.Event()
                i = 0
                for timestamp,resource_key,resource_value in my_driver.GetState(blocking=True, terminate=terminate):
                    process(timestamp, resource_key, resource_value)
                    i += 1
                    if i == 10: terminate.set()

                # just retrieve accumulated samples
                samples = my_driver.GetState(blocking=False, terminate=terminate)
                # or (as classical loop)
                i = 0
                for timestamp,resource_key,resource_value in my_driver.GetState(blocking=False, terminate=terminate):
                    process(timestamp, resource_key, resource_value)
                    i += 1
                    if i == 10: terminate.set()
            Parameters:
                blocking : bool
                    Select the driver behaviour. In both cases, the driver will first retrieve the samples accumulated
                    and available in the internal queue. Then, if blocking, the driver does not terminate the loop and
                    waits for additional samples to come, thus behaving as a generator. If non-blocking, the driver
                    terminates the loop and returns. Non-blocking behaviour can be used for periodically polling the
                    driver, while blocking can be used when a separate thread is in charge of collecting the samples
                    produced by the driver.
                terminate : threading.Event
                    Signals the interruption of the GetState method as soon as possible.
            Returns:
                results : Iterator[Tuple[float, str, Any]]
                    Sequences of state sample. Each State sample contains a float Unix-like timestamps of the samples in
                    seconds with up to microsecond resolution, the resource_key of the sample, and its resource_value.
                    Only resources with an active subscription must be retrieved. Interval and duration of the sampling
                    process are specified when creating the subscription using method SubscribeState(). Order of values
                    yielded is arbitrary.
        """
        raise NotImplementedError()
