swadhinbiswas 📧 fix: mail module cleanup - remove dead code, simplify error handling · 7/25/2026
58c2a3e
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use lettre::{
message::{header::ContentType, Mailbox, Message, MessageBuilder, MultiPart, SinglePart},
transport::smtp::authentication::Credentials,
AsyncSmtpTransport, AsyncTransport, Tokio1Executor,
};
use tokio::sync::OnceCell;
use super::{EmailMessage, SmtpConfig};
/// Wraps a lettre SMTP transport behind a OnceCell for lazy initialization.
/// Clone is cheap (just Arc-like via OnceCell).
#[derive(Clone)]
pub struct SmtpSender {
config: SmtpConfig,
transport: std::sync::Arc<OnceCell<AsyncSmtpTransport<Tokio1Executor>>>,
}
impl std::fmt::Debug for SmtpSender {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("SmtpSender").field("host", &self.config.host).finish()
}
}
impl SmtpSender {
pub fn new(config: SmtpConfig) -> Self {
Self { config, transport: std::sync::Arc::new(OnceCell::new()) }
}
async fn get_transport(
&self,
) -> Result<AsyncSmtpTransport<Tokio1Executor>, lettre::transport::smtp::Error> {
self.transport
.get_or_try_init(|| async {
let builder = if self.config.use_tls {
AsyncSmtpTransport::<Tokio1Executor>::relay(&self.config.host)?
} else {
AsyncSmtpTransport::<Tokio1Executor>::builder_dangerous(&self.config.host)
.port(self.config.port)
};
let mut builder = builder;
if let (Some(user), Some(pass)) = (&self.config.username, &self.config.password) {
builder = builder.credentials(Credentials::new(user.clone(), pass.clone()));
}
Ok::<_, lettre::transport::smtp::Error>(builder.build())
})
.await
.cloned()
}
fn mailbox(addr: &super::EmailAddress) -> Mailbox {
addr.name
.clone()
.map(|n| Mailbox::new(Some(n), addr.address.parse().unwrap()))
.unwrap_or_else(|| Mailbox::new(None, addr.address.parse().unwrap()))
}
fn add_recipients(
builder: MessageBuilder,
addrs: &[super::EmailAddress],
kind: RecipientKind,
) -> MessageBuilder {
let mut b = builder;
for addr in addrs {
let mailbox = Self::mailbox(addr);
b = match kind {
RecipientKind::To => b.to(mailbox),
RecipientKind::Cc => b.cc(mailbox),
RecipientKind::Bcc => b.bcc(mailbox),
};
}
b
}
fn build_lettre_message(&self, msg: &EmailMessage) -> Result<Message, anyhow::Error> {
let from = Self::mailbox(&self.config.default_from);
let builder = Message::builder().from(from);
let builder = Self::add_recipients(builder, &msg.to, RecipientKind::To);
let builder = Self::add_recipients(builder, &msg.cc, RecipientKind::Cc);
let builder = Self::add_recipients(builder, &msg.bcc, RecipientKind::Bcc);
let builder = if let Some(reply) = &msg.reply_to {
builder.reply_to(Self::mailbox(reply))
} else {
builder
};
let builder = builder.subject(&msg.subject);
let has_attachments = !msg.attachments.is_empty();
let has_both = msg.text_body.is_some() && msg.html_body.is_some();
if has_attachments || has_both {
let mut multipart = MultiPart::mixed().build();
if has_both {
let alt = MultiPart::alternative()
.singlepart(SinglePart::plain(msg.text_body.as_ref().unwrap().clone()))
.singlepart(SinglePart::html(msg.html_body.as_ref().unwrap().clone()));
multipart = multipart.multipart(alt);
} else if let Some(text) = &msg.text_body {
multipart = multipart.singlepart(SinglePart::plain(text.clone()));
} else if let Some(html) = &msg.html_body {
multipart = multipart.singlepart(SinglePart::html(html.clone()));
}
for att in &msg.attachments {
let ct: ContentType = att
.content_type
.parse()
.unwrap_or_else(|_| ContentType::parse("application/octet-stream").unwrap());
let part = SinglePart::builder().header(ct).body(att.data.clone());
multipart = multipart.singlepart(part);
}
builder.multipart(multipart)
} else if let Some(html) = &msg.html_body {
builder.body(html.clone())
} else {
builder.body(msg.text_body.clone().unwrap_or_default())
}
.map_err(|e| anyhow::anyhow!("Failed to build email: {e}"))
}
pub async fn send(&self, msg: &EmailMessage) -> Result<(), anyhow::Error> {
let lettre_msg = self.build_lettre_message(msg)?;
let transport = self.get_transport().await?;
transport.send(lettre_msg).await?;
Ok(())
}
}
enum RecipientKind {
To,
Cc,
Bcc,
}