"""
Safe configuration wrapper for Course Teams feature.
"""


import re
from enum import Enum

import six
from django.utils.functional import cached_property

# "Arbitrarily large" but still limited
MANAGED_TEAM_MAX_TEAM_SIZE = 200
# Arbitrarily arbitrary
DEFAULT_COURSE_RUN_MAX_TEAM_SIZE = 50


class TeamsConfig(object):
    """
    Configuration for the Course Teams feature on a course run.

    Takes in a configuration from a JSON-friendly dictionary,
    and exposes cleaned data from it.
    """
    def __init__(self, data):
        """
        Initialize a TeamsConfig object with a dictionary.
        """
        self._data = data if isinstance(data, dict) else {}

    def __unicode__(self):
        """
        Return user-friendly string.

        TODO move this code to __str__ after Py3 upgrade.
        """
        return "Teams configuration for {} team-sets".format(len(self.teamsets))

    def __str__(self):
        """
        Return user-friendly string.
        """
        return str(self.__unicode__())

    def __repr__(self):
        """
        Return developer-helpful string.
        """
        return "<{} default_max_team_size={} teamsets=[{}]>".format(
            self.__class__.__name__,
            self.default_max_team_size,
            ", ".join(repr(teamset) for teamset in self.teamsets),
        )

    def __eq__(self, other):
        """
        Define equality based on cleaned data.
        """
        return isinstance(other, self.__class__) and self.cleaned_data == other.cleaned_data

    def __ne__(self, other):
        """
        Overrides default inequality to be the inverse of our custom equality.
        Safe to remove once we're in Python 3 -- Py3 does this for us.
        """
        return not self.__eq__(other)

    @property
    def source_data(self):
        """
        Dictionary containing the data from which this TeamsConfig was built.
        """
        return self._data

    @cached_property
    def cleaned_data(self):
        """
        JSON-friendly dictionary containing cleaned data from this TeamsConfig.
        """
        return {
            'max_team_size': self.default_max_team_size,
            'team_sets': [
                teamset.cleaned_data for teamset in self.teamsets
            ]
        }

    @property
    def is_enabled(self):
        """
        Whether the Course Teams feature is enabled for this course run.
        """
        return bool(self.teamsets)

    @cached_property
    def teamsets(self):
        """
        List of configurations for team-sets.

        A team-set is a logical collection of teams, generally centered around a
        discussion topic or assignment.

        A learner should be able to join one team per team-set
        (TODO MST-12... currently, a learner may join one team per course).
        """
        all_teamsets_data = self._data.get(
            'team_sets',
            # For backwards compatibility, also check "topics" key.
            self._data.get('topics', [])
        )
        if not isinstance(all_teamsets_data, list):
            return []
        all_teamsets = [
            TeamsetConfig(teamset_data)
            for teamset_data in all_teamsets_data
        ]
        good_teamsets = []
        seen_ids = set()
        for teamset in all_teamsets:
            if teamset.teamset_id and teamset.teamset_id not in seen_ids:
                good_teamsets.append(teamset)
                seen_ids.add(teamset.teamset_id)
        return good_teamsets

    @cached_property
    def teamsets_by_id(self):
        return {teamset.teamset_id: teamset for teamset in self.teamsets}

    @cached_property
    def default_max_team_size(self):
        """
        The default maximum size for teams in this course.

        Can be overriden by individual team sets; see `calc_max_team_size`.
        """
        return _clean_max_team_size(self._data.get('max_team_size')) or DEFAULT_COURSE_RUN_MAX_TEAM_SIZE

    def calc_max_team_size(self, teamset_id):
        """
        Given a team-set's ID, return the maximum allowed size of teams within it.

        For 'open' team-sets, first regards the team-set's `max_team_size`,
        then falls back to the course's `max_team_size`.
        For managed team-sets, returns `MANAGED_TEAM_MAX_TEAM_SIZE`
        (a number that is big enough to never really be a limit, but does put an upper limit for safety's sake)

        Return value of None should be regarded as "no maximum size" (TODO MST-33).
        """
        try:
            teamset = self.teamsets_by_id[teamset_id]
        except KeyError:
            raise ValueError("Team-set {!r} does not exist.".format(teamset_id))  # lint-amnesty, pylint: disable=raise-missing-from
        if teamset.teamset_type != TeamsetType.open:
            return MANAGED_TEAM_MAX_TEAM_SIZE
        if teamset.max_team_size:
            return teamset.max_team_size
        return self.default_max_team_size


class TeamsetConfig(object):
    """
    Configuration for a team-set within a course run.

    Takes in a configuration from a JSON-friendly dictionary,
    and exposes cleaned data from it.
    """
    teamset_id_regex = re.compile(r'^[A-Za-z0-9_. -]+$')

    def __init__(self, data):
        """
        Initialize a TeamsConfig object with a dictionary.
        """
        self._data = data if isinstance(data, dict) else {}

    def __unicode__(self):
        """
        Return user-friendly string.

        TODO move this code to __str__ after Py3 upgrade.
        """
        return self.name

    def __str__(self):
        """
        Return user-friendly string.
        """
        return str(self.__unicode__())

    def __repr__(self):
        """
        Return developer-helpful string.
        """
        attrs = ['teamset_id', 'name', 'description', 'max_team_size', 'teamset_type']
        return "<{} {}>".format(
            self.__class__.__name__,
            " ".join(
                attr + "=" + repr(getattr(self, attr))
                for attr in attrs if hasattr(self, attr)
            ),
        )

    def __eq__(self, other):
        """
        Define equality based on cleaned data.
        """
        return isinstance(other, self.__class__) and self.cleaned_data == other.cleaned_data

    def __ne__(self, other):
        """
        Overrides default inequality to be the inverse of our custom equality.
        Safe to remove once we're in Python 3 -- Py3 does this for us.
        """
        return not self.__eq__(other)

    @property
    def source_data(self):
        """
        Dictionary containing the data from which this TeamsConfig was built.
        """
        return self._data

    @cached_property
    def cleaned_data(self):
        """
        JSON-friendly dictionary containing cleaned data from this TeamsConfig.
        """
        return {
            'id': self.teamset_id,
            'name': self.name,
            'description': self.description,
            'max_team_size': self.max_team_size,
            'type': self.teamset_type.value,
        }

    @cached_property
    def teamset_id(self):
        """
        An identifier for this team-set.

        Should be a URL-slug friendly string,
        but for a historical reasons may contain periods and spaces.
        """
        teamset_id = _clean_string(self._data.get('id'))
        if not self.teamset_id_regex.match(teamset_id):
            return ""
        return teamset_id

    @cached_property
    def name(self):
        """
        A human-friendly name of the team-set,
        falling back to `teamset_id`.
        """
        return _clean_string(self._data.get('name')) or self.teamset_id

    @cached_property
    def description(self):
        """
        A brief description of the team-set,
        falling back to empty string.
        """
        return _clean_string(self._data.get('description'))

    @cached_property
    def max_team_size(self):
        """
        Configured maximum team size override for this team-set,
        falling back to None.
        """
        return _clean_max_team_size(self._data.get('max_team_size'))

    @cached_property
    def teamset_type(self):
        """
        Configured TeamsetType,
        falling back to default TeamsetType.
        """
        try:
            return TeamsetType(self._data['type'])
        except (KeyError, ValueError):
            return TeamsetType.get_default()

    @cached_property
    def is_private_managed(self):
        """
        Returns true if teamsettype is private_managed
        """
        return self.teamset_type == TeamsetType.private_managed


class TeamsetType(Enum):
    """
    Management and privacy scheme for teams within a team-set.

    "open" team-sets allow learners to freely join, leave, and create teams.

    "public_managed" team-sets forbid learners from modifying teams' membership.
    Instead, instructors manage membership (TODO MST-9).

    "private_managed" is like public_managed, except for that team names,
    team memberships, and team discussions are all private to the members
    of the teams (TODO MST-10).
    """
    open = "open"
    public_managed = "public_managed"
    private_managed = "private_managed"

    @classmethod
    def get_default(cls):
        """
        Return default TeamsetType.
        """
        return cls.open


def _clean_string(value):
    """
    Return `str(value)` if it's a string or int, otherwise "".
    """
    if isinstance(value, six.integer_types + six.string_types):
        return six.text_type(value)
    return ""


def _clean_max_team_size(value):
    """
    Return `value` if it's a positive int, otherwise None.
    """
    if not isinstance(value, six.integer_types):
        return None
    if value < 0:
        return None
    return value