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

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

#    Copyright (C) 2012 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 abc

from taskflow.openstack.common import uuidutils
from taskflow import task
from taskflow import utils


def _class_name(obj):
    return ".".join([obj.__class__.__module__, obj.__class__.__name__])


class Flow(object):
    """The base abstract class of all flow implementations.

    It provides a name and an identifier (uuid or other) to the flow so that
    it can be uniquely identifed among many flows.

    Flows are expected to provide the following methods:
    - add
    - __len__
    """

    __metaclass__ = abc.ABCMeta

    def __init__(self, name, uuid=None):
        self._name = str(name)
        if uuid:
            self._id = str(uuid)
        else:
            self._id = uuidutils.generate_uuid()

    @property
    def name(self):
        """A non-unique name for this flow (human readable)"""
        return self._name

    @property
    def uuid(self):
        return self._id

    @abc.abstractmethod
    def __len__(self):
        """Returns how many items are in this flow."""
        raise NotImplementedError()

    def __str__(self):
        lines = ["%s: %s" % (_class_name(self), self.name)]
        lines.append("%s" % (self.uuid))
        lines.append("%s" % (len(self)))
        return "; ".join(lines)

    def _extract_item(self, item):
        if isinstance(item, (task.BaseTask, Flow)):
            return item
        if issubclass(item, task.BaseTask):
            return item()
        task_factory = getattr(item, utils.TASK_FACTORY_ATTRIBUTE, None)
        if task_factory:
            return self._extract_item(task_factory(item))
        raise TypeError("Invalid item %r: it's not task and not flow" % item)

    @abc.abstractmethod
    def add(self, *items):
        """Adds a given item/items to this flow."""
        raise NotImplementedError()

    @abc.abstractproperty
    def requires(self):
        """Browse flow requirements."""

    @abc.abstractproperty
    def provides(self):
        """Browse values provided by the flow."""