# -*- encoding: utf-8 -*-
# Copyright (c) 2015 b<>com
#
# 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.

"""
A :ref:`Strategy <strategy_definition>` is an algorithm implementation which is
able to find a :ref:`Solution <solution_definition>` for a given
:ref:`Goal <goal_definition>`.

There may be several potential strategies which are able to achieve the same
:ref:`Goal <goal_definition>`. This is why it is possible to configure which
specific :ref:`Strategy <strategy_definition>` should be used for each
:ref:`Goal <goal_definition>`.

Some strategies may provide better optimization results but may take more time
to find an optimal :ref:`Solution <solution_definition>`.

When a new :ref:`Goal <goal_definition>` is added to the Watcher configuration,
at least one default associated :ref:`Strategy <strategy_definition>` should be
provided as well.

:ref:`Some default implementations are provided <watcher_strategies>`, but it
is possible to :ref:`develop new implementations <implement_strategy_plugin>`
which are dynamically loaded by Watcher at launch time.
"""

import abc
import six

from watcher.common import clients
from watcher.common import context
from watcher.common import exception
from watcher.common.loader import loadable
from watcher.common import utils
from watcher.decision_engine.loading import default as loading
from watcher.decision_engine.model.collector import manager
from watcher.decision_engine.scope import default as default_scope
from watcher.decision_engine.solution import default
from watcher.decision_engine.strategy.common import level


@six.add_metaclass(abc.ABCMeta)
class BaseStrategy(loadable.Loadable):
    """A base class for all the strategies

    A Strategy is an algorithm implementation which is able to find a
    Solution for a given Goal.
    """

    def __init__(self, config, osc=None):
        """Constructor: the signature should be identical within the subclasses

        :param config: Configuration related to this plugin
        :type config: :py:class:`~.Struct`
        :param osc: An OpenStackClients instance
        :type osc: :py:class:`~.OpenStackClients` instance
        """
        super(BaseStrategy, self).__init__(config)
        self.ctx = context.make_context()
        self._name = self.get_name()
        self._display_name = self.get_display_name()
        self._goal = self.get_goal()
        # default strategy level
        self._strategy_level = level.StrategyLevel.conservative
        self._cluster_state_collector = None
        # the solution given by the strategy
        self._solution = default.DefaultSolution(goal=self.goal, strategy=self)
        self._osc = osc
        self._collector_manager = None
        self._compute_model = None
        self._input_parameters = utils.Struct()
        self._audit_scope = None
        self._audit_scope_handler = None

    @classmethod
    @abc.abstractmethod
    def get_name(cls):
        """The name of the strategy"""
        raise NotImplementedError()

    @classmethod
    @abc.abstractmethod
    def get_display_name(cls):
        """The goal display name for the strategy"""
        raise NotImplementedError()

    @classmethod
    @abc.abstractmethod
    def get_translatable_display_name(cls):
        """The translatable msgid of the strategy"""
        # Note(v-francoise): Defined here to be used as the translation key for
        # other services
        raise NotImplementedError()

    @classmethod
    @abc.abstractmethod
    def get_goal_name(cls):
        """The goal name the strategy achieves"""
        raise NotImplementedError()

    @classmethod
    def get_goal(cls):
        """The goal the strategy achieves"""
        goal_loader = loading.DefaultGoalLoader()
        return goal_loader.load(cls.get_goal_name())

    @classmethod
    def get_config_opts(cls):
        """Defines the configuration options to be associated to this loadable

        :return: A list of configuration options relative to this Loadable
        :rtype: list of :class:`oslo_config.cfg.Opt` instances
        """
        return []

    @abc.abstractmethod
    def pre_execute(self):
        """Pre-execution phase

        This can be used to fetch some pre-requisites or data.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def do_execute(self):
        """Strategy execution phase

        This phase is where you should put the main logic of your strategy.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    def post_execute(self):
        """Post-execution phase

        This can be used to compute the global efficacy
        """
        raise NotImplementedError()

    def execute(self):
        """Execute a strategy

        :return: A computed solution (via a placement algorithm)
        :rtype: :py:class:`~.BaseSolution` instance
        """
        self.pre_execute()
        self.do_execute()
        self.post_execute()

        self.solution.compute_global_efficacy()

        return self.solution

    @property
    def collector_manager(self):
        if self._collector_manager is None:
            self._collector_manager = manager.CollectorManager()
        return self._collector_manager

    @property
    def compute_model(self):
        """Cluster data model

        :returns: Cluster data model the strategy is executed on
        :rtype model: :py:class:`~.ModelRoot` instance
        """
        if self._compute_model is None:
            collector = self.collector_manager.get_cluster_model_collector(
                'compute', osc=self.osc)
            self._compute_model = self.audit_scope_handler.get_scoped_model(
                collector.get_latest_cluster_data_model())

        if not self._compute_model:
            raise exception.ClusterStateNotDefined()

        if self._compute_model.stale:
            raise exception.ClusterStateStale()

        return self._compute_model

    @classmethod
    def get_schema(cls):
        """Defines a Schema that the input parameters shall comply to

        :return: A jsonschema format (mandatory default setting)
        :rtype: dict
        """
        return {}

    @property
    def input_parameters(self):
        return self._input_parameters

    @input_parameters.setter
    def input_parameters(self, p):
        self._input_parameters = p

    @property
    def osc(self):
        if not self._osc:
            self._osc = clients.OpenStackClients()
        return self._osc

    @property
    def solution(self):
        return self._solution

    @solution.setter
    def solution(self, s):
        self._solution = s

    @property
    def audit_scope(self):
        return self._audit_scope

    @audit_scope.setter
    def audit_scope(self, s):
        self._audit_scope = s

    @property
    def audit_scope_handler(self):
        if not self._audit_scope_handler:
            self._audit_scope_handler = default_scope.DefaultScope(
                self.audit_scope)
        return self._audit_scope_handler

    @property
    def name(self):
        return self._name

    @property
    def display_name(self):
        return self._display_name

    @property
    def goal(self):
        return self._goal

    @property
    def strategy_level(self):
        return self._strategy_level

    @strategy_level.setter
    def strategy_level(self, s):
        self._strategy_level = s

    @property
    def state_collector(self):
        return self._cluster_state_collector

    @state_collector.setter
    def state_collector(self, s):
        self._cluster_state_collector = s


@six.add_metaclass(abc.ABCMeta)
class DummyBaseStrategy(BaseStrategy):

    @classmethod
    def get_goal_name(cls):
        return "dummy"


@six.add_metaclass(abc.ABCMeta)
class UnclassifiedStrategy(BaseStrategy):
    """This base class is used to ease the development of new strategies

    The goal defined within this strategy can be used to simplify the
    documentation explaining how to implement a new strategy plugin by
    ommitting the need for the strategy developer to define a goal straight
    away.
    """

    @classmethod
    def get_goal_name(cls):
        return "unclassified"


@six.add_metaclass(abc.ABCMeta)
class ServerConsolidationBaseStrategy(BaseStrategy):

    @classmethod
    def get_goal_name(cls):
        return "server_consolidation"


@six.add_metaclass(abc.ABCMeta)
class ThermalOptimizationBaseStrategy(BaseStrategy):

    @classmethod
    def get_goal_name(cls):
        return "thermal_optimization"


@six.add_metaclass(abc.ABCMeta)
class WorkloadStabilizationBaseStrategy(BaseStrategy):

    @classmethod
    def get_goal_name(cls):
        return "workload_balancing"