from django.apps import apps
from django.contrib.auth.models import Permission
from django.db.models import Q

from ..utils.auth import GROUP_ADMIN_PK, GROUP_DEFAULT_PK
from .models import Group, User


def get_permission_change_data(sender, permissions=None, **kwargs):
    """
    Yields all necessary collections if 'users.can_see_name' permission changes.
    """
    users_app = apps.get_app_config(app_label='users')
    for permission in permissions:
        # There could be only one 'users.can_see_name' and then we want to return data.
        if permission.content_type.app_label == users_app.label and permission.codename == 'can_see_name':
            yield from users_app.get_startup_elements()


def create_builtin_groups_and_admin(**kwargs):
    """
    Creates the builtin groups: Default, Delegates, Staff and Committees.

    Creates the builtin user: admin.
    """
    # Check whether there are groups in the database.
    if Group.objects.exists():
        # Do completely nothing if there are already some groups in the database.
        return

    permission_strings = (
        'agenda.can_be_speaker',
        'agenda.can_manage',
        'agenda.can_manage_list_of_speakers',
        'agenda.can_see',
        'agenda.can_see_internal_items',
        'assignments.can_manage',
        'assignments.can_nominate_other',
        'assignments.can_nominate_self',
        'assignments.can_see',
        'core.can_manage_config',
        'core.can_manage_logos_and_fonts',
        'core.can_manage_projector',
        'core.can_manage_tags',
        'core.can_manage_chat',
        'core.can_see_frontpage',
        'core.can_see_projector',
        'core.can_use_chat',
        'mediafiles.can_manage',
        'mediafiles.can_see',
        'mediafiles.can_see_hidden',
        'mediafiles.can_upload',
        'motions.can_create',
        'motions.can_manage',
        'motions.can_manage_metadata',
        'motions.can_see',
        'motions.can_support',
        'users.can_manage',
        'users.can_see_extra_data',
        'users.can_see_name', )
    permission_query = Q()
    permission_dict = {}

    # Load all permissions
    for permission_string in permission_strings:
        app_label, codename = permission_string.split('.')
        query_part = Q(content_type__app_label=app_label) & Q(codename=codename)
        permission_query = permission_query | query_part
    for permission in Permission.objects.select_related('content_type').filter(permission_query):
        permission_string = '.'.join((permission.content_type.app_label, permission.codename))
        permission_dict[permission_string] = permission

    # Default (pk 1 == GROUP_DEFAULT_PK)
    base_permissions = (
        permission_dict['agenda.can_see'],
        permission_dict['agenda.can_see_internal_items'],
        permission_dict['assignments.can_see'],
        permission_dict['core.can_see_frontpage'],
        permission_dict['core.can_see_projector'],
        permission_dict['mediafiles.can_see'],
        permission_dict['motions.can_see'],
        permission_dict['users.can_see_name'], )
    group_default = Group(pk=GROUP_DEFAULT_PK, name='Default')
    group_default.save(skip_autoupdate=True)
    group_default.permissions.add(*base_permissions)

    # Admin (pk 2 == GROUP_ADMIN_PK)
    group_admin = Group(pk=GROUP_ADMIN_PK, name='Admin')
    group_admin.save(skip_autoupdate=True)

    # Delegates (pk 3)
    delegates_permissions = (
        permission_dict['agenda.can_see'],
        permission_dict['agenda.can_see_internal_items'],
        permission_dict['agenda.can_be_speaker'],
        permission_dict['assignments.can_see'],
        permission_dict['assignments.can_nominate_other'],
        permission_dict['assignments.can_nominate_self'],
        permission_dict['core.can_see_frontpage'],
        permission_dict['core.can_see_projector'],
        permission_dict['mediafiles.can_see'],
        permission_dict['motions.can_see'],
        permission_dict['motions.can_create'],
        permission_dict['motions.can_support'],
        permission_dict['users.can_see_name'], )
    group_delegates = Group(pk=3, name='Delegates')
    group_delegates.save(skip_autoupdate=True)
    group_delegates.permissions.add(*delegates_permissions)

    # Staff (pk 4)
    staff_permissions = (
        permission_dict['agenda.can_see'],
        permission_dict['agenda.can_see_internal_items'],
        permission_dict['agenda.can_be_speaker'],
        permission_dict['agenda.can_manage'],
        permission_dict['agenda.can_manage_list_of_speakers'],
        permission_dict['assignments.can_see'],
        permission_dict['assignments.can_manage'],
        permission_dict['assignments.can_nominate_other'],
        permission_dict['assignments.can_nominate_self'],
        permission_dict['core.can_see_frontpage'],
        permission_dict['core.can_see_projector'],
        permission_dict['core.can_manage_projector'],
        permission_dict['core.can_manage_tags'],
        permission_dict['core.can_use_chat'],
        permission_dict['mediafiles.can_see'],
        permission_dict['mediafiles.can_manage'],
        permission_dict['mediafiles.can_upload'],
        permission_dict['motions.can_see'],
        permission_dict['motions.can_create'],
        permission_dict['motions.can_manage'],
        permission_dict['motions.can_manage_metadata'],
        permission_dict['users.can_see_name'],
        permission_dict['users.can_manage'],
        permission_dict['users.can_see_extra_data'],
        permission_dict['mediafiles.can_see_hidden'],)
    group_staff = Group(pk=4, name='Staff')
    group_staff.save(skip_autoupdate=True)
    group_staff.permissions.add(*staff_permissions)

    # Committees (pk 5)
    committees_permissions = (
        permission_dict['agenda.can_see'],
        permission_dict['agenda.can_see_internal_items'],
        permission_dict['assignments.can_see'],
        permission_dict['core.can_see_frontpage'],
        permission_dict['core.can_see_projector'],
        permission_dict['mediafiles.can_see'],
        permission_dict['motions.can_see'],
        permission_dict['motions.can_create'],
        permission_dict['motions.can_support'],
        permission_dict['users.can_see_name'], )
    group_committee = Group(pk=5, name='Committees')
    group_committee.save(skip_autoupdate=True)
    group_committee.permissions.add(*committees_permissions)

    # Create or reset admin user
    User.objects.create_or_reset_admin_user()

    # After each group was created, the permissions (many to many fields) where
    # added to the group. But we do not have to update the cache by calling
    # inform_changed_data() because the cache is updated on server start.