feat: Implement mailer service for sending emails

src/service/Cargo.toml

@@ -123,6 +123,7 @@ blurhash.workspace = true
 blurhash.optional = true
 recaptcha-verify = { version = "0.2.0", default-features = false }
 yansi.workspace = true
+lettre.workspace = true
 
 [target.'cfg(all(unix, target_os = "linux"))'.dependencies]
 sd-notify.workspace = true

src/service/mailer/messages.rs

@@ -0,0 +1,48 @@
+use askama::Template;
+use ruma::UserId;
+
+pub trait MessageTemplate: Template {
+	fn subject(&self) -> String;
+}
+
+#[derive(Template)]
+#[template(path = "mail/change_email.txt.j2")]
+pub struct ChangeEmail<'a> {
+	user_id: &'a UserId,
+	verification_link: &'a str,
+}
+
+impl MessageTemplate for ChangeEmail<'_> {
+	fn subject(&self) -> String { "Verify your email address".to_owned() }
+}
+
+#[derive(Template)]
+#[template(path = "mail/new_account.txt.j2")]
+pub struct NewAccount<'a> {
+	server_name: &'a str,
+	verification_link: &'a str,
+}
+
+impl MessageTemplate for NewAccount<'_> {
+	fn subject(&self) -> String { "Create your new Matrix account".to_owned() }
+}
+
+#[derive(Template)]
+#[template(path = "mail/password_reset.txt.j2")]
+pub struct PasswordReset<'a> {
+	display_name: &'a str,
+	user_id: &'a UserId,
+	verification_link: &'a str,
+}
+
+impl MessageTemplate for PasswordReset<'_> {
+	fn subject(&self) -> String { format!("Password reset request for {}", &self.user_id) }
+}
+
+#[derive(Template)]
+#[template(path = "mail/test.txt.j2")]
+pub struct Test;
+
+impl MessageTemplate for Test {
+	fn subject(&self) -> String { "Test message".to_owned() }
+}

src/service/mailer/mod.rs

@@ -0,0 +1,102 @@
+use std::sync::Arc;
+
+use conduwuit::{Err, Result, err, info};
+use lettre::{
+	AsyncSmtpTransport, AsyncTransport, Tokio1Executor,
+	message::{Mailbox, MessageBuilder},
+};
+
+use crate::{Args, mailer::messages::MessageTemplate};
+
+pub mod messages;
+
+type Transport = AsyncSmtpTransport<Tokio1Executor>;
+type TransportError = lettre::transport::smtp::Error;
+
+pub struct Service {
+	transport: Option<(Mailbox, Transport)>,
+}
+
+#[async_trait::async_trait]
+impl crate::Service for Service {
+	fn build(args: Args<'_>) -> Result<Arc<Self>> {
+		let transport = args
+			.server
+			.config
+			.smtp
+			.as_ref()
+			.map(|config| {
+				Ok((config.sender.clone(), Transport::from_url(&config.connection_uri)?.build()))
+			})
+			.transpose()
+			.map_err(|err: TransportError| err!("Failed to set up SMTP transport: {err}"))?;
+
+		Ok(Arc::new(Self { transport }))
+	}
+
+	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
+
+	async fn worker(self: Arc<Self>) -> Result<()> {
+		if let Some((_, ref transport)) = self.transport {
+			match transport.test_connection().await {
+				| Ok(true) => {
+					info!("SMTP connection test successful");
+					Ok(())
+				},
+				| Ok(false) => {
+					Err!("SMTP connection test failed")
+				},
+				| Err(err) => {
+					Err!("SMTP connection test failed: {err}")
+				},
+			}
+		} else {
+			info!("SMTP is not configured, email functionality will be unavailable");
+			Ok(())
+		}
+	}
+}
+
+impl Service {
+	/// Returns a mailer which allows email to be sent, if SMTP is configured.
+	#[must_use]
+	pub fn mailer(&self) -> Option<Mailer<'_>> {
+		self.transport
+			.as_ref()
+			.map(|(sender, transport)| Mailer { sender, transport })
+	}
+}
+
+pub struct Mailer<'a> {
+	sender: &'a Mailbox,
+	transport: &'a Transport,
+}
+
+impl Mailer<'_> {
+	/// Sends an email.
+	pub async fn send<Template: MessageTemplate>(
+		&self,
+		recipient: Mailbox,
+		message: Template,
+	) -> Result<()> {
+		let subject = message.subject();
+		let body = message
+			.render()
+			.map_err(|err| err!("Failed to render message template: {err}"))?;
+
+		let message = MessageBuilder::new()
+			.from(self.sender.clone())
+			.to(recipient)
+			.subject(subject)
+			.date_now()
+			.body(body)
+			.expect("should have been able to construct message");
+
+		self.transport
+			.send(message)
+			.await
+			.map_err(|err: TransportError| err!("Failed to send message: {err}"))?;
+
+		Ok(())
+	}
+}

src/service/mod.rs

@@ -21,6 +21,7 @@ pub mod federation;
 pub mod firstrun;
 pub mod globals;
 pub mod key_backups;
+pub mod mailer;
 pub mod media;
 pub mod moderation;
 pub mod password_reset;

src/service/services.rs

@@ -9,7 +9,7 @@ use tokio::sync::Mutex;
 
 use crate::{
 	account_data, admin, announcements, antispam, appservice, client, config, emergency,
-	federation, firstrun, globals, key_backups,
+	federation, firstrun, globals, key_backups, mailer,
 	manager::Manager,
 	media, moderation, password_reset, presence, pusher, registration_tokens, resolver, rooms,
 	sending, server_keys,
@@ -28,6 +28,7 @@ pub struct Services {
 	pub key_backups: Arc<key_backups::Service>,
 	pub media: Arc<media::Service>,
 	pub password_reset: Arc<password_reset::Service>,
+	pub mailer: Arc<mailer::Service>,
 	pub presence: Arc<presence::Service>,
 	pub pusher: Arc<pusher::Service>,
 	pub registration_tokens: Arc<registration_tokens::Service>,
@@ -83,6 +84,7 @@ impl Services {
 			key_backups: build!(key_backups::Service),
 			media: build!(media::Service),
 			password_reset: build!(password_reset::Service),
+			mailer: build!(mailer::Service),
 			presence: build!(presence::Service),
 			pusher: build!(pusher::Service),
 			registration_tokens: build!(registration_tokens::Service),

src/service/templates/mail/_base.txt.j2

@@ -0,0 +1,3 @@
+{%- block content %}{% endblock %}
+
+Message sent by Continuwuity {{ env!("CARGO_PKG_VERSION") }}. 🐈

src/service/templates/mail/change_email.txt.j2

@@ -0,0 +1,10 @@
+{% extends "_base.txt.j2" %}
+
+{% block content -%}
+Hello!
+
+Somebody, probably you, tried to associate this email address with the Matrix account {{ user_id }}.
+If that's your account, and this is your email address, click this link to proceed:
+    {{ verification_link }}
+Otherwise, you can ignore this email. The above link will expire in one hour.
+{%- endblock %}

src/service/templates/mail/new_account.txt.j2

@@ -0,0 +1,10 @@
+{% extends "_base.txt.j2" %}
+
+{% block content -%}
+Hello!
+
+Somebody, probably you, tried to create a Matrix account on {{ server_name }} using this email address.
+Use the link below to proceed with creating your account:
+    {{ verification_link }}
+If you are not trying to create an account, you can ignore this email. The above link will expire in one hour.
+{%- endblock %}

src/service/templates/mail/password_reset.txt.j2

@@ -0,0 +1,10 @@
+{% extends "_base.txt.j2" %}
+
+{% block content -%}
+Hello {{ display_name }} ({{ user_id }}),
+
+Somebody, probably you, tried to reset your Matrix account's password.
+If you requested for your password to be reset, click this link to proceed:
+    {{ verification_link }}
+Otherwise, you can ignore this email. The above link will expire in one hour.
+{%- endblock %}

src/service/templates/mail/test.txt.j2

@@ -0,0 +1,5 @@
+{% extends "_base.txt.j2" %}
+
+{% block content -%}
+If you're seeing this, SMTP is configured correctly. :3
+{%- endblock %}