# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You 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.

"""
Operation contexts.
"""

import threading
from contextlib import contextmanager

import aria
from aria.utils import file
from . import common


class BaseOperationContext(common.BaseContext):
    """
    Base class for contexts used during operation creation and execution.
    """

    def __init__(self, task_id, actor_id, **kwargs):
        self._task_id = task_id
        self._actor_id = actor_id
        self._thread_local = threading.local()
        self._destroy_session = kwargs.pop('destroy_session', False)
        logger_level = kwargs.pop('logger_level', None)
        super(BaseOperationContext, self).__init__(**kwargs)
        self._register_logger(task_id=self.task.id, level=logger_level)

    def __repr__(self):
        details = u'function={task.function}; ' \
                  u'operation_arguments={task.arguments}'\
            .format(task=self.task)
        return u'{name}({0})'.format(details, name=self.name)

    @property
    def task(self):
        """
        The task in the model storage.
        """
        # SQLAlchemy prevents from accessing an object which was created on a different thread.
        # So we retrieve the object from the storage if the current thread isn't the same as the
        # original thread.

        if not hasattr(self._thread_local, 'task'):
            self._thread_local.task = self.model.task.get(self._task_id)
        return self._thread_local.task

    @property
    def plugin_workdir(self):
        """
        A work directory that is unique to the plugin and the service ID.
        """
        if self.task.plugin is None:
            return None
        plugin_workdir = u'{0}/plugins/{1}/{2}'.format(self._workdir,
                                                       self.service.id,
                                                       self.task.plugin.name)
        file.makedirs(plugin_workdir)
        return plugin_workdir

    @property
    def serialization_dict(self):
        context_dict = {
            'name': self.name,
            'service_id': self._service_id,
            'task_id': self._task_id,
            'actor_id': self._actor_id,
            'workdir': self._workdir,
            'model_storage': self.model.serialization_dict if self.model else None,
            'resource_storage': self.resource.serialization_dict if self.resource else None,
            'execution_id': self._execution_id,
            'logger_level': self.logger.level
        }
        return {
            'context_cls': self.__class__,
            'context': context_dict
        }

    @classmethod
    def instantiate_from_dict(cls, model_storage=None, resource_storage=None, **kwargs):
        if model_storage:
            model_storage = aria.application_model_storage(**model_storage)
        if resource_storage:
            resource_storage = aria.application_resource_storage(**resource_storage)

        return cls(model_storage=model_storage,
                   resource_storage=resource_storage,
                   destroy_session=True,
                   **kwargs)

    def close(self):
        if self._destroy_session:
            self.model.log._session.remove()
            self.model.log._engine.dispose()

    @property
    @contextmanager
    def persist_changes(self):
        yield
        self.model.task.update(self.task)


class NodeOperationContext(BaseOperationContext):
    """
    Context for node operations.
    """

    @property
    def node(self):
        """
        The node of the current operation.
        """
        return self.model.node.get(self._actor_id)

    @property
    def node_template(self):
        """
        The node template of the current operation.
        """
        return self.node.node_template


class RelationshipOperationContext(BaseOperationContext):
    """
    Context for relationship operations.
    """

    @property
    def relationship(self):
        """
        The relationship instance of the current operation.
        """
        return self.model.relationship.get(self._actor_id)

    @property
    def source_node(self):
        """
        The relationship source node.
        """
        return self.relationship.source_node

    @property
    def source_node_template(self):
        """
        The relationship source node template.
        """
        return self.source_node.node_template

    @property
    def target_node(self):
        """
        The relationship target node.
        """
        return self.relationship.target_node

    @property
    def target_node_template(self):
        """
        The relationship target node template.
        """
        return self.target_node.node_template