# -*- coding: utf-8 -*-

# vim: tabstop=4 shiftwidth=4 softtabstop=4

#    Copyright (C) 2013 Yahoo! Inc. All Rights Reserved.
#
#    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 six

from taskflow import states as st


class GraphAnalyzer(object):
    """Analyzes graph to get next nodes for execution or reversion"""

    def __init__(self, graph, storage):
        self._graph = graph
        self._storage = storage

    @property
    def graph(self):
        return self._graph

    def browse_nodes_for_execute(self, node=None):
        """Browse next nodes to execute for given node if
           specified and for whole graph otherwise.
        """
        if node:
            nodes = self._graph.successors(node)
        else:
            nodes = self._graph.nodes_iter()

        available_nodes = []
        for node in nodes:
            if self._is_ready_for_execute(node):
                available_nodes.append(node)
        return available_nodes

    def browse_nodes_for_revert(self, node=None):
        """Browse next nodes to revert for given node if
           specified and for whole graph otherwise.
        """
        if node:
            nodes = self._graph.predecessors(node)
        else:
            nodes = self._graph.nodes_iter()

        available_nodes = []
        for node in nodes:
            if self._is_ready_for_revert(node):
                available_nodes.append(node)
        return available_nodes

    def _is_ready_for_execute(self, task):
        """Checks if task is ready to be executed"""

        state = self._storage.get_task_state(task.name)
        if not st.check_task_transition(state, st.RUNNING):
            return False

        task_names = []
        for prev_task in self._graph.predecessors(task):
            task_names.append(prev_task.name)

        task_states = self._storage.get_tasks_states(task_names)
        return all(state == st.SUCCESS
                   for state in six.itervalues(task_states))

    def _is_ready_for_revert(self, task):
        """Checks if task is ready to be reverted"""

        state = self._storage.get_task_state(task.name)
        if not st.check_task_transition(state, st.REVERTING):
            return False

        task_names = []
        for prev_task in self._graph.successors(task):
            task_names.append(prev_task.name)

        task_states = self._storage.get_tasks_states(task_names)
        return all(state in (st.PENDING, st.REVERTED)
                   for state in six.itervalues(task_states))