from django.contrib import messages

from .forms import EmailTemplateForm, HiddenDataForm


class MailEditorMixin:
    """
    Use MailEditorMixin in edit CBVs to automatically implement the mail editor as
    a post-form_valid hook.

    The view must specify the `mail_code` variable.
    """
    object = None
    mail_form = None
    has_permission_to_send_mail = True

    def __init__(self, *args, **kwargs):
        if not self.mail_code:
            raise AttributeError(self.__class__.__name__ + ' object has no attribute `mail_code`')
        super().__init__(*args, **kwargs)

    def get_template_names(self):
        """
        The mail editor form has its own template.
        """
        if self.mail_form and not self.mail_form.is_valid():
            return ['mails/mail_form.html']
        return super().get_template_names()

    def post(self, request, *args, **kwargs):
        """
        Handle POST requests, but interpect the data if the mail form data isn't valid.
        """
        if not self.has_permission_to_send_mail:
            # Don't use the mail form; don't send out the mail.
            return super().post(request, *args, **kwargs)
        self.object = self.get_object()
        form = self.get_form()
        if form.is_valid():
            self.mail_form = EmailTemplateForm(request.POST or None,
                                               mail_code=self.mail_code,
                                               instance=self.object)
            if self.mail_form.is_valid():
                return self.form_valid(form)

            return self.render_to_response(
                self.get_context_data(form=self.mail_form,
                                      transfer_data_form=HiddenDataForm(form)))
        else:
            return self.form_invalid(form)

    def form_valid(self, form):
        """
        If both the regular form and mailing form are valid, save the form and run the mail form.
        """
        # Don't use the mail form; don't send out the mail.
        if not self.has_permission_to_send_mail:
            return super().form_valid(form)

        try:
            self.mail_form.send()
        except AttributeError:
            # self.mail_form is None
            raise AttributeError('Did you check the order in which MailEditorMixin is used?')
        messages.success(self.request, 'Mail sent')
        return super().form_valid(form)


class MailUtilsMixin:
    """
    This mixin takes care of inserting the default data into the Utils or Form.
    """