//! The log transport: each message becomes one file under `<data_dir>/mail-log/`. For development
//! and tests (`[mail] transport = "log"`). The files hold the full body, one-time links included,
//! so this transport is not for production.

use std::path::PathBuf;

use forge_core::mail::{MailError, OutgoingMail};

use super::{Mailer, SendFuture};

/// Writes messages to a directory.
pub struct LogMailer {
    dir: PathBuf,
}

impl LogMailer {
    pub fn new(dir: PathBuf) -> LogMailer {
        LogMailer { dir }
    }

    async fn write(&self, mail: &OutgoingMail) -> Result<(), MailError> {
        tokio::fs::create_dir_all(&self.dir)
            .await
            .map_err(|e| MailError::Transient(format!("cannot create the mail log: {e}")))?;
        let name = format!("{}.txt", ulid::Ulid::generate());
        let mut text = format!("To: {}\nSubject: {}\n", mail.to, mail.subject);
        if let Some(id) = &mail.message_id {
            text.push_str(&format!("Message-ID: {id}\n"));
        }
        if let Some(parent) = &mail.in_reply_to {
            text.push_str(&format!("In-Reply-To: {parent}\nReferences: {parent}\n"));
        }
        text.push_str(&format!("\n{}", mail.body));
        tokio::fs::write(self.dir.join(name), text)
            .await
            .map_err(|e| MailError::Transient(format!("cannot write the mail log: {e}")))
    }
}

impl Mailer for LogMailer {
    fn send<'a>(&'a self, mail: &'a OutgoingMail) -> SendFuture<'a> {
        Box::pin(self.write(mail))
    }
}