from custommail.shortcuts import send_mass_custom_mail
from smtplib import SMTPRecipientsRefused


def drop_until(predicate, l):
    """
    Drop the first elements of the list until we find the first element
    satisfying the predicate, this element is also dropped.
    """
    for i in range(len(l)):
        if predicate(l[i]):
            return l[i + 1:]
    return []


def intersects(list1, list2):
    """ Return True iff there is one element in common in the two lists """
    return any(x in list2 for x in list1)


class SendMassMailRecipientRefused(Exception):
    pass


def send_mass_custom_mail_wrapper(datatuple, *args, **kwargs):
    """
    Similar to custommail.shortcuts.send_mass_custom_mail but if an
    SMTPRecipientsRefused exception is encountered, finish processing the datatuple
    and only raise at the end of the list.
    Thus, only the faulty emails won't be sent.
    """
    to_be_sent = datatuple
    in_error = []

    while to_be_sent:
        try:
            send_mass_custom_mail(to_be_sent, *args, **kwargs)
            to_be_sent = []
        except SMTPRecipientsRefused as exn:
            # A recipient error has been encountered:
            # 1. drop already sent emails from the "to be sent" list
            # 2. move the bogus email from the "to be sent" list to the "in error" list
            # 3. try to send the remaining emails
            refused_emails, = exn.args

            def predicate(tuple):
                __, __, __, recipients = tuple
                return intersects(refused_emails.keys(), recipients)

            to_be_sent = drop_until(predicate, to_be_sent)
            in_error.append(refused_emails)

    if in_error:
        raise SendMassMailRecipientRefused(in_error)