"""
Tools for sending email.
"""
from django.conf import settings
# Imported for backwards compatibility and for the sake
# of a cleaner namespace. These symbols used to be in
# django/core/mail.py before the introduction of email
# backends and the subsequent reorganization (See #10355)
from django.core.mail.message import (
    DEFAULT_ATTACHMENT_MIME_TYPE, BadHeaderError, EmailMessage,
    EmailMultiAlternatives, SafeMIMEMultipart, SafeMIMEText,
    forbid_multi_line_headers, make_msgid,
)
from django.core.mail.utils import DNS_NAME, CachedDnsName
from django.utils.module_loading import import_string

__all__ = [
    'CachedDnsName', 'DNS_NAME', 'EmailMessage', 'EmailMultiAlternatives',
    'SafeMIMEText', 'SafeMIMEMultipart', 'DEFAULT_ATTACHMENT_MIME_TYPE',
    'make_msgid', 'BadHeaderError', 'forbid_multi_line_headers',
    'get_connection', 'send_mail', 'send_mass_mail', 'mail_admins',
    'mail_managers',
]


def get_connection(backend=None, fail_silently=False, **kwds):
    """Load an email backend and return an instance of it.

    If backend is None (default), use settings.EMAIL_BACKEND.

    Both fail_silently and other keyword arguments are used in the
    constructor of the backend.
    """
    klass = import_string(backend or settings.EMAIL_BACKEND)
    return klass(fail_silently=fail_silently, **kwds)


def send_mail(subject, message, from_email, recipient_list,
              fail_silently=False, auth_user=None, auth_password=None,
              connection=None, html_message=None):
    """
    Easy wrapper for sending a single message to a recipient list. All members
    of the recipient list will see the other recipients in the 'To' field.

    If from_email is None, use the DEFAULT_FROM_EMAIL setting.
    If auth_user is None, use the EMAIL_HOST_USER setting.
    If auth_password is None, use the EMAIL_HOST_PASSWORD setting.

    Note: The API for this method is frozen. New code wanting to extend the
    functionality should use the EmailMessage class directly.
    """
    connection = connection or get_connection(
        username=auth_user,
        password=auth_password,
        fail_silently=fail_silently,
    )
    mail = EmailMultiAlternatives(subject, message, from_email, recipient_list, connection=connection)
    if html_message:
        mail.attach_alternative(html_message, 'text/html')

    return mail.send()


def send_mass_mail(datatuple, fail_silently=False, auth_user=None,
                   auth_password=None, connection=None):
    """
    Given a datatuple of (subject, message, from_email, recipient_list), send
    each message to each recipient list. Return the number of emails sent.

    If from_email is None, use the DEFAULT_FROM_EMAIL setting.
    If auth_user and auth_password are set, use them to log in.
    If auth_user is None, use the EMAIL_HOST_USER setting.
    If auth_password is None, use the EMAIL_HOST_PASSWORD setting.

    Note: The API for this method is frozen. New code wanting to extend the
    functionality should use the EmailMessage class directly.
    """
    connection = connection or get_connection(
        username=auth_user,
        password=auth_password,
        fail_silently=fail_silently,
    )
    messages = [
        EmailMessage(subject, message, sender, recipient, connection=connection)
        for subject, message, sender, recipient in datatuple
    ]
    return connection.send_messages(messages)


def mail_admins(subject, message, fail_silently=False, connection=None,
                html_message=None):
    """Send a message to the admins, as defined by the ADMINS setting."""
    if not settings.ADMINS:
        return
    if not all(isinstance(a, (list, tuple)) and len(a) == 2 for a in settings.ADMINS):
        raise ValueError('The ADMINS setting must be a list of 2-tuples.')
    mail = EmailMultiAlternatives(
        '%s%s' % (settings.EMAIL_SUBJECT_PREFIX, subject), message,
        settings.SERVER_EMAIL, [a[1] for a in settings.ADMINS],
        connection=connection,
    )
    if html_message:
        mail.attach_alternative(html_message, 'text/html')
    mail.send(fail_silently=fail_silently)


def mail_managers(subject, message, fail_silently=False, connection=None,
                  html_message=None):
    """Send a message to the managers, as defined by the MANAGERS setting."""
    if not settings.MANAGERS:
        return
    if not all(isinstance(a, (list, tuple)) and len(a) == 2 for a in settings.MANAGERS):
        raise ValueError('The MANAGERS setting must be a list of 2-tuples.')
    mail = EmailMultiAlternatives(
        '%s%s' % (settings.EMAIL_SUBJECT_PREFIX, subject), message,
        settings.SERVER_EMAIL, [a[1] for a in settings.MANAGERS],
        connection=connection,
    )
    if html_message:
        mail.attach_alternative(html_message, 'text/html')
    mail.send(fail_silently=fail_silently)
