Split multiplart email sending into a dedicated handler (#9977)

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

2 files changed, 108 insertions, 45 deletions

diff --git a/synapse/handlers/account_validity.py b/synapse/handlers/account_validity.py
index 5b927f10b3..d752cf34f0 100644
--- a/synapse/handlers/account_validity.py
+++ b/synapse/handlers/account_validity.py
@@ -15,12 +15,9 @@
 import email.mime.multipart
 import email.utils
 import logging
-from email.mime.multipart import MIMEMultipart
-from email.mime.text import MIMEText
 from typing import TYPE_CHECKING, List, Optional, Tuple
 
 from synapse.api.errors import StoreError, SynapseError
-from synapse.logging.context import make_deferred_yieldable
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.types import UserID
 from synapse.util import stringutils
@@ -36,9 +33,11 @@ class AccountValidityHandler:
         self.hs = hs
         self.config = hs.config
         self.store = self.hs.get_datastore()
-        self.sendmail = self.hs.get_sendmail()
+        self.send_email_handler = self.hs.get_send_email_handler()
         self.clock = self.hs.get_clock()
 
+        self._app_name = self.hs.config.email_app_name
+
         self._account_validity_enabled = (
             hs.config.account_validity.account_validity_enabled
         )
@@ -63,23 +62,10 @@ class AccountValidityHandler:
             self._template_text = (
                 hs.config.account_validity.account_validity_template_text
             )
-            account_validity_renew_email_subject = (
+            self._renew_email_subject = (
                 hs.config.account_validity.account_validity_renew_email_subject
             )
 
-            try:
-                app_name = hs.config.email_app_name
-
-                self._subject = account_validity_renew_email_subject % {"app": app_name}
-
-                self._from_string = hs.config.email_notif_from % {"app": app_name}
-            except Exception:
-                # If substitution failed, fall back to the bare strings.
-                self._subject = account_validity_renew_email_subject
-                self._from_string = hs.config.email_notif_from
-
-            self._raw_from = email.utils.parseaddr(self._from_string)[1]
-
             # Check the renewal emails to send and send them every 30min.
             if hs.config.run_background_tasks:
                 self.clock.looping_call(self._send_renewal_emails, 30 * 60 * 1000)
@@ -159,38 +145,17 @@ class AccountValidityHandler:
         }
 
         html_text = self._template_html.render(**template_vars)
-        html_part = MIMEText(html_text, "html", "utf8")
-
         plain_text = self._template_text.render(**template_vars)
-        text_part = MIMEText(plain_text, "plain", "utf8")
 
         for address in addresses:
             raw_to = email.utils.parseaddr(address)[1]
 
-            multipart_msg = MIMEMultipart("alternative")
-            multipart_msg["Subject"] = self._subject
-            multipart_msg["From"] = self._from_string
-            multipart_msg["To"] = address
-            multipart_msg["Date"] = email.utils.formatdate()
-            multipart_msg["Message-ID"] = email.utils.make_msgid()
-            multipart_msg.attach(text_part)
-            multipart_msg.attach(html_part)
-
-            logger.info("Sending renewal email to %s", address)
-
-            await make_deferred_yieldable(
-                self.sendmail(
-                    self.hs.config.email_smtp_host,
-                    self._raw_from,
-                    raw_to,
-                    multipart_msg.as_string().encode("utf8"),
-                    reactor=self.hs.get_reactor(),
-                    port=self.hs.config.email_smtp_port,
-                    requireAuthentication=self.hs.config.email_smtp_user is not None,
-                    username=self.hs.config.email_smtp_user,
-                    password=self.hs.config.email_smtp_pass,
-                    requireTransportSecurity=self.hs.config.require_transport_security,
-                )
+            await self.send_email_handler.send_email(
+                email_address=raw_to,
+                subject=self._renew_email_subject,
+                app_name=self._app_name,
+                html=html_text,
+                text=plain_text,
             )
 
         await self.store.set_renewal_mail_status(user_id=user_id, email_sent=True)
diff --git a/synapse/handlers/send_email.py b/synapse/handlers/send_email.py
new file mode 100644
index 0000000000..e9f6aef06f
--- /dev/null
+++ b/synapse/handlers/send_email.py
@@ -0,0 +1,98 @@
+# Copyright 2021 The Matrix.org C.I.C. Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import email.utils
+import logging
+from email.mime.multipart import MIMEMultipart
+from email.mime.text import MIMEText
+from typing import TYPE_CHECKING
+
+from synapse.logging.context import make_deferred_yieldable
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class SendEmailHandler:
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+
+        self._sendmail = hs.get_sendmail()
+        self._reactor = hs.get_reactor()
+
+        self._from = hs.config.email.email_notif_from
+        self._smtp_host = hs.config.email.email_smtp_host
+        self._smtp_port = hs.config.email.email_smtp_port
+        self._smtp_user = hs.config.email.email_smtp_user
+        self._smtp_pass = hs.config.email.email_smtp_pass
+        self._require_transport_security = hs.config.email.require_transport_security
+
+    async def send_email(
+        self,
+        email_address: str,
+        subject: str,
+        app_name: str,
+        html: str,
+        text: str,
+    ) -> None:
+        """Send a multipart email with the given information.
+
+        Args:
+            email_address: The address to send the email to.
+            subject: The email's subject.
+            app_name: The app name to include in the From header.
+            html: The HTML content to include in the email.
+            text: The plain text content to include in the email.
+        """
+        try:
+            from_string = self._from % {"app": app_name}
+        except (KeyError, TypeError):
+            from_string = self._from
+
+        raw_from = email.utils.parseaddr(from_string)[1]
+        raw_to = email.utils.parseaddr(email_address)[1]
+
+        if raw_to == "":
+            raise RuntimeError("Invalid 'to' address")
+
+        html_part = MIMEText(html, "html", "utf8")
+        text_part = MIMEText(text, "plain", "utf8")
+
+        multipart_msg = MIMEMultipart("alternative")
+        multipart_msg["Subject"] = subject
+        multipart_msg["From"] = from_string
+        multipart_msg["To"] = email_address
+        multipart_msg["Date"] = email.utils.formatdate()
+        multipart_msg["Message-ID"] = email.utils.make_msgid()
+        multipart_msg.attach(text_part)
+        multipart_msg.attach(html_part)
+
+        logger.info("Sending email to %s" % email_address)
+
+        await make_deferred_yieldable(
+            self._sendmail(
+                self._smtp_host,
+                raw_from,
+                raw_to,
+                multipart_msg.as_string().encode("utf8"),
+                reactor=self._reactor,
+                port=self._smtp_port,
+                requireAuthentication=self._smtp_user is not None,
+                username=self._smtp_user,
+                password=self._smtp_pass,
+                requireTransportSecurity=self._require_transport_security,
+            )
+        )