chatmail-core/src/smtp/send.rs

//! # SMTP message sending

use async_smtp::{EmailAddress, Envelope, SendableEmail};

use super::Smtp;
use crate::config::Config;
use crate::context::Context;
use crate::events::EventType;

pub type Result<T> = std::result::Result<T, Error>;

// if more recipients are needed in SMTP's `RCPT TO:` header, recipient-list is splitted to chunks.
// this does not affect MIME'e `To:` header.
// can be overwritten by the setting `max_smtp_rcpt_to` in provider-db.
pub(crate) const DEFAULT_MAX_SMTP_RCPT_TO: usize = 50;

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Envelope error: {}", _0)]
    Envelope(anyhow::Error),
    #[error("Send error: {}", _0)]
    SmtpSend(async_smtp::error::Error),
    #[error("SMTP has no transport")]
    NoTransport,
    #[error("{}", _0)]
    Other(#[from] anyhow::Error),
}

impl Smtp {
    /// Send a prepared mail to recipients.
    /// On successful send out Ok() is returned.
    pub async fn send(
        &mut self,
        context: &Context,
        recipients: &[EmailAddress],
        message: &[u8],
    ) -> Result<()> {
        if !context.get_config_bool(Config::Bot).await? {
            // Notify ratelimiter about sent message regardless of whether quota is exceeded or not.
            // Checking whether sending is allowed for low-priority messages should be done by the
            // caller.
            context.ratelimit.write().await.send();
        }

        let message_len_bytes = message.len();

        let chunk_size = context
            .get_configured_provider()
            .await?
            .and_then(|provider| provider.opt.max_smtp_rcpt_to)
            .map_or(DEFAULT_MAX_SMTP_RCPT_TO, usize::from);

        for recipients_chunk in recipients.chunks(chunk_size) {
            let recipients_display = recipients_chunk
                .iter()
                .map(|x| x.as_ref())
                .collect::<Vec<&str>>()
                .join(",");

            let envelope = Envelope::new(self.from.clone(), recipients_chunk.to_vec())
                .map_err(Error::Envelope)?;
            let mail = SendableEmail::new(envelope, message);

            if let Some(ref mut transport) = self.transport {
                transport.send(mail).await.map_err(Error::SmtpSend)?;

                context.emit_event(EventType::SmtpMessageSent(format!(
                    "Message len={message_len_bytes} was smtp-sent to {recipients_display}"
                )));
                self.last_success = Some(std::time::SystemTime::now());
            } else {
                warn!(
                    context,
                    "uh? SMTP has no transport, failed to send to {}", recipients_display
                );
                return Err(Error::NoTransport);
            }
        }
        Ok(())
    }
}