from django import forms
from django.contrib.auth.models import Group
from django.template.loader import render_to_string
from django.utils.functional import cached_property
from django.utils.translation import ugettext_lazy as _

from wagtail.wagtailusers.forms import GroupPagePermissionFormSet

from utils.forms import KeepUnselectableModelFormMixin

from kfet.auth.fields import BasePermissionsField
from kfet.auth.models import Permission


class CmsGroupForm(KeepUnselectableModelFormMixin, forms.ModelForm):
    """
    Allow to change permissions related to the cms of a `Group` object.
    """
    access_admin = forms.BooleanField(
        label=_("Accès à l'administration"),
        required=False,
        help_text=_(
            "<b>Attention :</b> Aucun paramétrage effectué dans cette section "
            "n'aura d'effet si cette case est décochée."
        ),
    )

    class Meta:
        model = Group
        fields = ()

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        group = self.instance

        if group.pk is not None:
            self.fields['access_admin'].initial = (
                group.permissions.filter(pk=self.access_admin_perm.pk).exists()
            )

    def save(self):
        group = super().save()

        if self.cleaned_data['access_admin']:
            group.permissions.add(self.access_admin_perm)
        else:
            group.permissions.remove(self.access_admin_perm)

        return group

    @cached_property
    def access_admin_perm(self):
        return Permission.objects.get(
            content_type__app_label='wagtailadmin',
            codename='access_admin',
        )


class SnippetsCmsGroupForm(KeepUnselectableModelFormMixin, forms.ModelForm):
    permissions = BasePermissionsField(
        label='',
        queryset=Permission.kfetcms.all(),
    )

    class Meta:
        model = Group
        fields = ('permissions',)


def prepare_page_permissions_formset(pages):
    """
    Create a new formset from base `GroupPagePermissionFormSet` Wagtail
    formset.

    - The choices of `pages` field of forms are limited to `pages`.
    - If there is no initial data, add an initial with the first collection
        selected.
    - Make 'as_admin_panel' use a custom template.

    Arguments
        pages (iterable of `Page`)

    Returns
        A formset to select group permissions of pages.

    """
    class RestrictedFormSet(GroupPagePermissionFormSet):

        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)

            # Remove forms cache, as theirs options are changed.
            del self.forms

            # 'initial' must be setup before accessing 'forms'.

            self.initial = list(
                filter(lambda i: i['page'] in pages, self.initial))

            # This is just little kindness.
            if not self.initial and pages:
                self.initial = [{'page': pages[0]}]

            for form in self.forms:
                self.customize_form(form)

        @property
        def empty_form(self):
            form = super().empty_form
            self.customize_form(form)
            return form

        def customize_form(self, form):
            # Widget must be setup before queryset.
            form.fields['page'].widget = forms.Select()
            form.fields['page'].queryset = pages
            # Force use of `CheckboxInput` for `DELETE` field, as `HiddenInput`
            # is not compatible with `django-formset-js`.
            form.fields['DELETE'].widget = forms.CheckboxInput()

        def as_admin_panel(self):
            # http://docs.wagtail.io/en/latest/reference/hooks.html#register-group-permission-panel
            template = 'kfet/permissions/page_permissions_formset.html'
            return render_to_string(template, {'formset': self})

    return RestrictedFormSet


def prepare_collection_member_permissions_formset(formset_cls, collections):
    """
    Create a new formset from base `formset_cls`.

    - The choices of `collections` field of forms produced by `formset_cls` are
        limited to `collections`.
    - If there is no initial data, add an initial with the first collection
        selected.
    - Make 'as_admin_panel' use a custom template.

    Arguments
        formset_cls (subclass of
            `wagtail.wagtailcore.forms`
            `.BaseGroupCollectionMemberPermissionFormSet`
        ):
            Formset to select group permissions of a collection member model.
            It should be rerieved from the `group_permission_panel` Wagtail
            hook. This includes the `Document` and `Image` models of Wagtail.
        collections (iterable of `wagtail.wagtailcore.models.Collection`)

    Returns
        A formset to select group permissions of collection-related models.

    """
    class RestrictedFormSet(formset_cls):

        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)

            # Remove forms cache, as theirs options are changed.
            del self.forms

            # 'initial' must be setup before accessing 'forms'.

            self.initial = list(
                filter(lambda i: i['collection'] in collections, self.initial))

            # This is just little kindness.
            if not self.initial and collections:
                self.initial = [{'collection': collections[0]}]

            for form in self.forms:
                self.customize_form(form)

        @property
        def empty_form(self):
            form = super().empty_form
            self.customize_form(form)
            return form

        def customize_form(self, form):
            form.fields['collection'].queryset = collections
            # Force use of `CheckboxInput` for `DELETE` field, as `HiddenInput`
            # is not compatible with `django-formset-js`.
            form.fields['DELETE'].widget = forms.CheckboxInput()

        def as_admin_panel(self):
            template = (
                'kfet/permissions/collection_member_permissions_formset.html')
            model = self.permission_queryset[0].content_type.model_class()
            return render_to_string(template, {
                'formset': self,
                'model_name': model._meta.verbose_name_plural,
            })

    return RestrictedFormSet