ic-bn-lib 0.2.2

use std::{borrow::Cow, fmt::Write as _, str::FromStr};

use smtp_proto::{
    RCPT_NOTIFY_DELAY, RCPT_NOTIFY_FAILURE, RCPT_NOTIFY_NEVER, RCPT_NOTIFY_SUCCESS, RcptTo,
};
use tracing::{debug, info};

use crate::{
    network::AsyncReadWrite,
    smtp::{
        ProtocolError, RecipientPolicy, RecipientResolveError,
        address::EmailAddress,
        inbound::{MAX_REPLY_LEN, Session, SessionResult},
    },
    truncate,
};

impl<S: AsyncReadWrite> Session<S> {
    /// Handles RCPT TO command
    pub async fn handle_rcpt_to(&mut self, to: RcptTo<Cow<'_, str>>) -> SessionResult<()> {
        let Some(mail_from) = &self.data.mail_from else {
            self.set_error(ProtocolError::InvalidSequenceOfCommands(
                "RCPT TO before MAIL FROM".into(),
            ));
            return self
                .reply("503", "5.5.1", "MAIL FROM is required first.")
                .await;
        };

        // Check if DSN-related stuff was requested
        if (to.flags
            & (RCPT_NOTIFY_DELAY | RCPT_NOTIFY_NEVER | RCPT_NOTIFY_SUCCESS | RCPT_NOTIFY_FAILURE))
            != 0
            || to.orcpt.is_some()
        {
            return self.ext_unsupported("DSN").await;
        }

        let Ok(address) = EmailAddress::from_str(&to.address) else {
            info!("{self}: {}: incorrect address", to.address);
            self.set_error(ProtocolError::RecipientValidationFailed(format!(
                "Incorrect address: {}",
                to.address
            )));
            return self.reply("550", "5.1.2", "Incorrect address.").await;
        };

        if self.data.rcpt_to.contains(&address) {
            return self.reply("250", "2.1.5", "OK").await;
        }

        if self.data.rcpt_to.len() >= self.cfg.max_recipients {
            info!("{self}: {}: too many recipients", to.address);
            self.set_error(ProtocolError::RecipientValidationFailed(format!(
                "Too many recipients: {} > {}",
                self.data.rcpt_to.len(),
                self.cfg.max_recipients
            )));
            return self.reply("455", "4.5.3", "Too many recipients.").await;
        }

        match self
            .cfg
            .recipient_resolver
            .resolve_recipient(mail_from, &address)
            .await
        {
            Ok(v) => {
                debug!("{self}: {}: recipient resolved: {v}", to.address);

                match v {
                    RecipientPolicy::Accept => {
                        self.data.rcpt_to.push(address);
                    }
                    RecipientPolicy::Rewrite(new_address) => {
                        self.data.rcpt_to.push(new_address);
                    }
                    RecipientPolicy::Expand(additional_addresses) => {
                        self.data.rcpt_to.push(address);
                        self.data.rcpt_to.extend(additional_addresses);
                    }
                }
            }

            Err(e) => {
                info!("{self}: {}: recipient resolution error: {e:#}", to.address);
                self.set_error(ProtocolError::RecipientValidationFailed(format!(
                    "Recipient resolution failed: {e:#}",
                )));

                return match e {
                    RecipientResolveError::UnknownDomain => {
                        self.reply("550", "5.1.1", "Unknown recipient domain.")
                            .await
                    }
                    RecipientResolveError::UnknownRecipient => {
                        self.reply("550", "5.1.2", "Mailbox does not exist.").await
                    }
                    // Truncate the errors so that they don't overflow the reply buffer
                    RecipientResolveError::Temporary(v) => {
                        self.reply_with("451", "4.4.3", |buf| {
                            write!(buf, "Temporary error: {}", truncate(&v, MAX_REPLY_LEN - 32))
                        })
                        .await
                    }
                    RecipientResolveError::Permanent(v) => {
                        self.reply_with("550", "5.1.3", |buf| {
                            write!(buf, "Permanent error: {}", truncate(&v, MAX_REPLY_LEN - 32))
                        })
                        .await
                    }
                };
            }
        }

        self.reply("250", "2.1.5", "OK").await
    }
}