File src/main.rs artifact 00cda9e50a part of check-in ac6ac8c108

//! Simple SMTP-to-Telegram gateway. Can parse email and send them as telegram
//! messages to specified chats, generally you specify which email address is
//! available in configuration, everything else is sent to default address.

use smol_macros::main;

use std::{
	os::unix::fs::PermissionsExt,
	path::Path,
};

use clap::Parser;
use smol::{
	fs::metadata,
};
use stacked_errors::{
	Result,
	StackableErr,
	bail,
};

use smtp2tg::mail::MailServer;

/// SMTP-to-Telegram gateway
#[derive(Parser, Debug)]
#[command(name = "smtp2tg")]
#[command(about = format!("SMTP-to-Telegram gateway v{}, (C) 2024 - 2026", env!("CARGO_PKG_VERSION")), long_about = None)]
struct Args {
	/// Set configuration file location
	#[arg(short, long, default_value = "smtp2tg.toml")]
	config: String,
}

main! {
/// Main asynchronous entry point for the application. Runs the gateway using
/// the configuration selected on the command line.
///
/// The configuration file must use owner-only permissions. Once configured,
/// the SMTP server runs until it stops or encounters an error.
///
/// # Errors
/// Returns an error if the configuration file is missing, inaccessible,
/// insecure, malformed, or contains invalid required settings.
///
/// # Panics
/// Panics if configuring or serving the SMTP server fails.
	async fn main () -> Result<()> {
		let args = Args::parse();
		let config_file = Path::new(&args.config);
		if !config_file.try_exists().stack()? {
			bail!("Configuration file not found: {config_file:?}\n\
				Hint: Ensure the file exists and the path is correct.");
		};
		{
			let meta = metadata(config_file).await.stack()?;
			if (!0o100600 & meta.permissions().mode()) > 0 {
				bail!("Configuration file permissions are insecure {config_file:?}\n\
					Current permissions: {:o}\n\
					Required: 0600 (owner read/write only).\n\
					Fix with: chmod 600 {config_file:?}",
					meta.permissions().mode());
		}	}
		let settings: config::Config = config::Config::builder()
			.set_default("api_gateway", "https://api.telegram.org").stack()?
			.set_default("fields", vec!["date", "from", "subject"]).stack()?
			.set_default("hostname", "smtp.2.tg").stack()?
			.set_default("listen_on", "0.0.0.0:1025").stack()?
			.set_default("domains", vec!["localhost",
				hostname::get().context("Failed to get current hostname")?
				.to_str().context("Can't convert hostname to string, bad UTF-8?")?]).stack()?
			.add_source(config::File::from(config_file))
			.build()
			.with_context(|| format!(
				"Failed to parse configuration file: {config_file:?}\n\
				Check syntax against smtp2tg.toml.example.\n\
				Common issues: missing quotes, trailing commas in inline tables, or invalid types."
			))?;

		let listen_on = settings.get_string("listen_on").stack()?;
		let server_name = settings.get_string("hostname").stack()?;
		let core = MailServer::new(settings)?;
		let mut server = mailin_embedded::Server::new(core);

		// TODO: remove unwraps when mailin-embedded bumps with better error handling
		server.with_name(server_name)
			.with_ssl(mailin_embedded::SslConfig::None).unwrap()
			.with_addr(listen_on).unwrap();
		server.serve().unwrap();

		Ok(())
}	}