Add SMTPService and Email helper

conftest.py

@@ -134,6 +134,12 @@ def mock_configuration(mocker):
                 "verify_ssl": False,
             },
             "redis_url": "redis://redis:@localhost:6379/",
+            "smtp": {
+                "host": "testserver",
+                "port": 12345,
+                "username": None,
+                "password": None,
+            },
         },
         "setup": {
             "codecov_url": "https://codecov.io",

helpers/email.py

@@ -0,0 +1,14 @@
+from email.message import EmailMessage
+
+
+class Email:
+    def __init__(
+        self, to_addr=None, from_addr=None, subject=None, text=None, html=None
+    ):
+        self.message = EmailMessage()
+        self.message["To"] = to_addr
+        self.message["From"] = from_addr
+        self.message["Subject"] = subject
+        self.message.set_content(text)
+        if html:
+            self.message.add_alternative(html, "text/html")

services/smtp.py

@@ -0,0 +1,131 @@
+import logging
+import smtplib
+import ssl
+
+from shared.config import get_config
+
+from helpers.email import Email
+
+log = logging.getLogger(__name__)
+
+
+class SMTPServiceError(Exception):
+    ...
+
+
+class SMTPService:
+    connection = None
+
+    @classmethod
+    def active(cls):
+        return cls.connection is not None
+
+    @property
+    def extra_dict(self):
+        return {"host": self.host, "port": self.port, "username": self.username}
+
+    def _load_config(self):
+        if get_config("services", "smtp", default={}) == {}:
+            return False
+        self.host = get_config("services", "smtp", "host", default="mailhog")
+        self.port = get_config("services", "smtp", "port", default=1025)
+        self.username = get_config("services", "smtp", "username", default=None)
+        self.password = get_config("services", "smtp", "password", default=None)
+        self.ssl_context = ssl.create_default_context()
+        return True
+
+    def tls_and_auth(self):
+        self.try_starttls()
+        if self.username and self.password:
+            self.try_login()
+
+    def try_starttls(self):
+        # only necessary if SMTP server supports TLS and authentication,
+        # for example mailhog does not need these two steps
+        try:
+            SMTPService.connection.starttls(context=self.ssl_context)
+        except smtplib.SMTPNotSupportedError:
+            log.warning(
+                "Server does not support TLS, continuing initialization of SMTP connection",
+                extra=dict(
+                    host=self.host,
+                    port=self.port,
+                    username=self.username,
+                    password=self.password,
+                ),
+            )
+        except smtplib.SMTPResponseException as exc:
+            log.warning("Error doing STARTTLS command on SMTP", extra=self.extra_dict)
+            raise SMTPServiceError("Error doing STARTTLS command on SMTP") from exc
+
+    def try_login(self):
+        try:
+            SMTPService.connection.login(self.username, self.password)
+        except smtplib.SMTPNotSupportedError:
+            log.warning(
+                "Server does not support AUTH, continuing initialization of SMTP connection",
+                extra=self.extra_dict,
+            )
+        except smtplib.SMTPAuthenticationError as exc:
+            log.warning(
+                "SMTP server did not accept username/password combination",
+                extra=self.extra_dict,
+            )
+            raise SMTPServiceError(
+                "SMTP server did not accept username/password combination"
+            ) from exc
+
+    def make_connection(self):
+        try:
+            SMTPService.connection.connect(self.host, self.port)
+        except smtplib.SMTPConnectError as exc:
+            raise SMTPServiceError("Error starting connection for SMTPService") from exc
+        self.tls_and_auth()
+
+    def __init__(self):
+        if not self._load_config():
+            log.warning("Unable to load SMTP config")
+            return
+        if SMTPService.connection is None:
+            try:
+                SMTPService.connection = smtplib.SMTP(
+                    host=self.host,
+                    port=self.port,
+                )
+
+            except smtplib.SMTPConnectError as exc:
+                raise SMTPServiceError(
+                    "Error starting connection for SMTPService"
+                ) from exc
+
+            self.tls_and_auth()
+
+    def send(self, email: Email):
+        if not SMTPService.connection:
+            self.make_connection()
+        else:
+            try:
+                SMTPService.connection.noop()
+            except smtplib.SMTPServerDisconnected:
+                self.make_connection()  # reconnect if disconnected
+        try:
+            errs = SMTPService.connection.send_message(
+                email.message,
+            )
+            if len(errs) != 0:
+                err_msg = " ".join(
+                    list(map(lambda err_tuple: f"{err_tuple[0]} {err_tuple[1]}", errs))
+                )
+                log.warning(f"Error sending email message: {err_msg}")
+                raise SMTPServiceError(f"Error sending email message: {err_msg}")
+        except smtplib.SMTPRecipientsRefused as exc:
+            log.warning("All recipients were refused", extra=self.extra_dict)
+            raise SMTPServiceError("All recipients were refused") from exc
+        except smtplib.SMTPSenderRefused as exc:
+            log.warning("Sender was refused", extra=self.extra_dict)
+            raise SMTPServiceError("Sender was refused") from exc
+        except smtplib.SMTPDataError as exc:
+            log.warning(
+                "The SMTP server did not accept the data", extra=self.extra_dict
+            )
+            raise SMTPServiceError("The SMTP server did not accept the data") from exc