telegraph_smtp.py

import json
import base64
import os
import email.parser
import email.policy
import paho.mqtt.client as mqtt
from aiosmtpd.controller import Controller


def on_connect(client, userdata, flags, rc):
    """
    Handles subscribing to topics when a connection to MQTT is established
    :return: None
    """
    print("Connected with result code "+str(rc), flush=True)


class TelegraphHandler:
    def __init__(self, mqtt: mqtt.Client):
        self.mqtt = mqtt

    async def handle_RCPT(self, server, session, envelope, address, rcpt_options):
        if address != 'post@home.misell.cymru':
            return '553 invalid email'
        envelope.rcpt_tos.append(address)
        return '250 OK'

    async def handle_DATA(self, server, session, envelope):
        print('Message from %s' % envelope.mail_from)
        print('Message for %s' % envelope.rcpt_tos)
        print('Message data:\n')
        print(envelope.content.decode('utf8', errors='replace'))
        print('End of message', flush=True)

        message = email.parser.BytesParser(policy=email.policy.default).parsebytes(envelope.content)
        message_body = message.get_body(preferencelist=('html', 'plain'))
        message_content = message_body.get_content()

        attachments = {}
        for part in message.walk():
            content_id = part.get("Content-ID")
            if content_id is None:
                continue
            content_id = content_id.strip()
            if not content_id.startswith("<"):
                continue
            if not content_id.endswith(">"):
                continue

            attachments[content_id[1:-1]] = {
                "type": part.get_content_type(),
                "data": base64.b64encode(part.get_content()).decode()
            }

        data = json.dumps({
            "subject": message["subject"],
            "from": message["from"],
            "message": message_content,
            "attachments": attachments
        })
        self.mqtt.publish("printer/print", data)

        return '250 Message accepted for delivery'


if __name__ == "__main__":
    client = mqtt.Client()
    client.on_connect = on_connect

    client.connect(os.getenv("MQTT_SERVER", "172.30.2.3"), 1883, 60)

    controller = Controller(TelegraphHandler(client), hostname='0.0.0.0', port=25)
    controller.start()
    print("SMTP server started", flush=True)
    while True:
        try:
            client.loop()
        except (KeyboardInterrupt, SystemExit):
            print("Bye!", flush=True)
            break
    controller.stop()