feat: Implement mailer service for sending emails

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(())
+	}
+}