influx-smtp-gateway/main.py

#!/usr/bin/env python3
"""
SMTP webhook server
"""

import os
import json
import smtplib
import sys
import time
from email.header import Header
from email.mime.text import MIMEText

import cherrypy
import logging
import threading


logging.basicConfig(stream=sys.stdout,
                    format='%(name)s - %(levelname)s - %(message)s')


def soft_return(msg):
    time.sleep(0.2)
    return(msg)


class SMTPWebhookApp:
    """
    SMTP webhook server
    """

    def create_new_client(self, response):
        try:
            mythread.client = smtplib.SMTP(host=SMTP_SERVER_HOST,
                                           port=SMTP_SERVER_PORT)
            mythread.client.starttls()
            return True
        except (smtplib.SMTPException, TimeoutError) as e:
            soft_return("can't connect")
            response = {"status": 500,  # noqa:F841
                        "message": "some error: {}".format(e)}
            return False

    def smtp_login(self, response, msg):
        try:
            mythread.client.login(msg["From"], FROM_MAIL_PASSWORD)
            return True
        except smtplib.SMTPException as e:
            soft_return(e)
            response = {"status": 500,  # noqa:F841
                        "message": "some error: {}".format(e)}
            return False

    def _send_mail(self):

        if not cherrypy.request.headers.get('Content-Length'):
            logging.error("error: Invalid content length.")
            return {"status": 400, "message": "Invalid content length."}

        cl = cherrypy.request.headers['Content-Length']
        rawbody = cherrypy.request.body.read(int(cl))
        req_body = json.loads(rawbody)

        if not req_body.get('subject') or req_body.get('subject') == '':
            logging.error("error: body field is required.")
            return {"status": 400, "message": "subject field is required."}

        if not req_body.get('body') or req_body.get('body') == '':
            logging.error("error: body field is required.")
            return {"status": 400, "message": "body field is required."}

        if not req_body.get('to_mail') or req_body.get('to_mail') == '':
            logging.error("error: to_mail field is required.")
            return {"status": 400, "message": "to_mail field is required."}

        subject = req_body['subject']
        body = req_body['body']
        to_mail = req_body['to_mail']

        msg = MIMEText(body, 'plain', 'utf-8')
        msg['Subject'] = Header(subject, 'utf-8')
        msg['From'] = FROM_MAIL
        msg['To'] = to_mail

        c = 0
        response = {}
        while (c < 2):
            try:
                mythread.client.sendmail(msg['From'],
                                         msg['To'], msg.as_string())
                response = {"status": 200, "message": "mail sent successfully"}
            except (AttributeError, ValueError,
                    smtplib.SMTPServerDisconnected):
                if (c == 1):
                    soft_return("can't connect")

                if not self.create_new_client(response):
                    break
                if not self.smtp_login(response, msg):
                    break

            except smtplib.SMTPException as e:
                soft_return("can't send for some reason")
                response = {"status": 500,
                            "message": "some error: {}".format(e)}
            finally:
                c += 1

        return response

    @cherrypy.expose
    def send_mail(self):
        """
        api endpoint for send mail
        """
        data = self._send_mail()
        cherrypy.response.status = data["status"]
        cherrypy.response.headers["Content-Type"] = "application/json"
        return json.dumps(data["status"]).encode()


ROOT = SMTPWebhookApp()
SMTP_SERVER_PORT = 587
CHERRYPY_SERVER_HOST = "0.0.0.0"
CHERRYPY_SERVER_PORT = 8081

if __name__ == "__main__":
    try:
        SMTP_SERVER_HOST = os.environ["SMTP_SERVER_HOST"]
        FROM_MAIL = os.environ["FROM_MAIL"]
        FROM_MAIL_PASSWORD = os.environ["FROM_MAIL_PASSWORD"]
    except KeyError:
        raise KeyError("Please check missing environment variables: "
                       "SMTP_SERVER_HOST, FROM_MAIL, "
                       "FROM_MAIL_PASSWORD")

    cherrypy.server.socket_host = CHERRYPY_SERVER_HOST
    cherrypy.server.socket_port = CHERRYPY_SERVER_PORT
    ENGINE = cherrypy.engine

    cherrypy.tree.mount(ROOT, config={})
    mythread = threading.local()
    mythread.client = None
    if hasattr(ENGINE, "signal_handler"):
        ENGINE.signal_handler.subscribe()
    if hasattr(ENGINE, "console_control_handler"):
        ENGINE.console_control_handler.subscribe()
    try:
        ENGINE.start()
    except Exception:  # pylint: disable=broad-except
        sys.exit(1)
    else:
        ENGINE.block()