from collections import defaultdict


from django import forms


import models
import transports
import widgets


class SubscriptionForm(forms.Form):
    def __init__(self, *args, **kwargs):
        self.user = kwargs.pop('user')
        self.site = kwargs.pop('site')
        self.categories = models.Category.objects.filter(site=self.site)
        self.subscriptions = models.Subscription.objects.filter(user=self.user)
        sub_by_category = defaultdict(lambda: [])
        for sub in self.subscriptions:
            sub_by_category[sub.category].append(sub.transport)
        super(SubscriptionForm, self).__init__(*args, **kwargs)
        self.choices = list(transports.get_transport_choices())
        for category in self.categories:
            field = forms.MultipleChoiceField(
                label=category.name, choices=self.choices,
                widget=widgets.CheckboxMultipleSelect,
                initial=sub_by_category[category],
                required=False)
            self.fields['category_%s' % category.identifier] = field

    def save(self):
        cleaned_data = self.cleaned_data
        wanted_subscriptions = set()
        for category in self.categories:
            field_id = 'category_%s' % category.identifier
            transports = cleaned_data.get(field_id, [])
            for transport in transports:
                wanted_subscriptions.add((category, transport))
        # delete dead subscriptions
        for subscription in self.subscriptions:
            pair = (subscription.category, subscription.transport)
            if pair not in wanted_subscriptions:
                subscription.delete()
        # create or update new ones
        for category, transport in wanted_subscriptions:
            models.Subscription.objects.get_or_create(
                user=self.user,
                category=category,
                transport=transport)