"""SMTP email backend class."""

import smtplib

import socket

import threading

from django.conf import settings

from django.core.mail.backends.base import BaseEmailBackend

from django.core.mail.utils import DNS_NAME

class EmailBackend(BaseEmailBackend):

    """

    A wrapper that manages the SMTP network connection.

    """

    def __init__(self, host=None, port=None, username=None, password=None,

                 use_tls=None, fail_silently=False, **kwargs):

        super(EmailBackend, self).__init__(fail_silently=fail_silently)

        self.host = host or settings.EMAIL_HOST

        self.port = port or settings.EMAIL_PORT

        self.username = username or settings.EMAIL_HOST_USER

        self.password = password or settings.EMAIL_HOST_PASSWORD

        if use_tls is None:

            self.use_tls = settings.EMAIL_USE_TLS

        else:

            self.use_tls = use_tls

        self.connection = None

        self._lock = threading.RLock()

    def open(self):

        """

        Ensures we have a connection to the email server. Returns whether or

        not a new connection was required (True or False).

        """

        if self.connection:

            # Nothing to do if the connection is already open.

            return False

        try:

            # If local_hostname is not specified, socket.getfqdn() gets used.

            # For performance, we use the cached FQDN for local_hostname.

            self.connection = smtplib.SMTP(self.host, self.port,

                                           local_hostname=DNS_NAME.get_fqdn())

            if self.use_tls:

                self.connection.ehlo()

                self.connection.starttls()

                self.connection.ehlo()

            if self.username and self.password:

                self.connection.login(self.username, self.password)

            return True

        except:

            if not self.fail_silently:

                raise

    def close(self):

        """Closes the connection to the email server."""

        try:

            try:

                self.connection.quit()

            except socket.sslerror:

                # This happens when calling quit() on a TLS connection

                # sometimes.

                self.connection.close()

            except:

                if self.fail_silently:

                    return

                raise

        finally:

            self.connection = None

    def send_messages(self, email_messages):

        """

        Sends one or more EmailMessage objects and returns the number of email

        messages sent.

        """

        if not email_messages:

            return

        self._lock.acquire()

        try:

            new_conn_created = self.open()

            if not self.connection:

                # We failed silently on open().

                # Trying to send would be pointless.

                return

            num_sent = 0

            for message in email_messages:

                sent = self._send(message)

                if sent:

                    num_sent += 1

            if new_conn_created:

                self.close()

        finally:

            self._lock.release()

        return num_sent

    def _send(self, email_message):

        """A helper method that does the actual sending."""

        if not email_message.recipients():

            return False

        try:

            self.connection.sendmail(email_message.from_email,

                    email_message.recipients(),

                    email_message.message().as_string())

        except:

            if not self.fail_silently:

                raise

            return False

        return True