import re
from itertools import groupby
from operator import attrgetter

from django import forms
from django.utils.translation import ugettext_lazy as _

from .models import Group, Permission

DEFAULT_PERMS = ['view', 'add', 'change', 'delete']

DEFAULT_PERMS_LABELS = {
    'view': _("Voir"),
    'add': _("Ajouter"),
    'change': _("Modifier"),
    'delete': _("Supprimer"),
}


class GroupsField(forms.ModelMultipleChoiceField):
    def __init__(self, **kwargs):
        kwargs.setdefault('queryset', Group.objects.all())
        kwargs.setdefault('widget', forms.CheckboxSelectMultiple)
        super().__init__(**kwargs)


class BasePermissionsField(forms.ModelMultipleChoiceField):
    def __init__(self, **kwargs):
        kwargs.setdefault('widget', forms.CheckboxSelectMultiple(attrs={
            'field_class': 'permissions-field',
        }))
        super().__init__(**kwargs)

        # Contain permissions grouped by `ContentType`. Used as choices for
        # this field.
        grouped_choices = []

        for ct, perms in groupby(self.queryset, attrgetter('content_type')):
            model_opts = ct.model_class()._meta
            choices = []

            # This helps for the default permissions, if they exists, to appear
            # at the beginning of the permissions list and use custom labels.
            reg_defaults_p = re.compile(
                r'^(?P<p_type>({defaults}))_{model_name}$'
                .format(
                    defaults='|'.join(DEFAULT_PERMS),
                    model_name=model_opts.model_name,
                )
            )
            next_default_pos = 0

            for p in perms:
                match = reg_defaults_p.match(p.codename)
                if match:
                    # `p` is a default permission. Use shorter label and insert
                    # after the last default permission seen in `choices`.
                    p_type = match.group('p_type')
                    choices.insert(
                        next_default_pos,
                        (p.id, DEFAULT_PERMS_LABELS[p_type])
                    )
                    next_default_pos += 1
                else:
                    # Non-default permissions. Use the permission description,
                    # instead of its `__str__`.
                    choices.append((p.id, p.name))

            grouped_choices.append((model_opts.verbose_name_plural, choices))

        self.choices = grouped_choices


class CorePermissionsField(BasePermissionsField):
    def __init__(self, **kwargs):
        kwargs.setdefault('queryset', Permission.kfetcore.all())
        super().__init__(**kwargs)