# vi:ft=toml:
# Telegram API key
api_key = "YOU_KNOW_WHERE_TO_GET_THIS"

# Telegram API gateway (when you are running your own)
api_gateway = "https://api.telegram.org" # <- note no trailing slash

# where to listen on (sockets are not supported since 0.3.0)
listen_on = "0.0.0.0:25"


# default hostname to use when serving requests


hostname = "smtp2tg"



# which domains are allowed in addresses
# this means that any unqualified recipient "somebody" will also match
# to "somebody@each_domain"
domains = [ "localhost", "current.hostname" ]

# default recipient, should be specified
# still can be a user, channel or group id
default = 0

# default fields to show in message header
fields = [ "date", "from", "subject" ]

[recipients]
# make sure you quote emails, as "@" can't go there unquoted. And by default
# we need FQDNs, also keep in mind emails are case insensitive
"somebody@example.com" = 1 # user id's are positive
"root" = -1 # group id's are negative

# to look up chat/group id you can use debug settings in Telegram clients,
# or some bot like @getidsbot or @RawDataBot

/// # Errors
/// Returns an error if configuration is invalid, files are inaccessible, or
/// server fails to start.
pub async fn async_main () -> Result<()> {
	let args = Args::parse();
	let config_file = Path::new(&args.config);
	if !config_file.exists() {
		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, 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

#[derive(Clone, Debug)]
pub struct MailServer {
	data: Vec<u8>,
	headers: Option<SomeHeaders>,
	tg: Arc<TelegramTransport>,
	fields: HashSet<String>,
	address: Regex,
	domains: HashSet<String>,
}

impl MailServer {
	/// Initializes the mail server: sets up the Telegram API client and
	/// validates all required configuration values.
	///
	/// # Arguments

		let mut domains: HashSet<String> = HashSet::new();
		let extra_domains = settings.get_array("domains").stack()?;
		for domain in extra_domains {
			let domain = domain.to_string().to_lowercase();
			if RE_DOMAIN.is_match(&domain) {
				domains.insert(domain);
			} else {
				bail!("Invalid domain in configuration: '{domain}'\n\
					Domains must be valid (e.g., 'example.com', 'localhost').\n\
					Check 'domains' array in smtp2tg.toml.");
		}	}

		if domains.is_empty() {
			bail!("No domains, need at least one: default `localhost` would do.");
		}
		let re_domains = domains.iter().map(|s| escape(s))
			.collect::<Vec<String>>().join("|");
		let address = RegexBuilder::new(&format!("^[a-z0-9][a-z0-9.-]*(@({re_domains}))?$"))
			.case_insensitive(true).build().stack()?;

		Ok(MailServer {
			data: vec!(),
			headers: None,
			tg,
			fields,
			address,
			domains,
		})
	}

	/// Retrieves the Telegram chat ID for a given email address, checks that
	/// used domain is allowed.
	///
	/// # Arguments
	/// * `name` - Email address or username to look up.
	///
	/// # Returns
	/// * `Result<ChatPeerId>` - Telegram chat ID for the address, or default if
	///   not found.
	pub fn get_id (&self, name: &str) -> Result<&ChatPeerId> {
		if self.address.is_match(name) {
			Ok(self.tg.get(name).unwrap_or(&self.tg.default))
		} else {
			bail!("Email address {name:?} is not from an allowed domain.");
	}	}


	/// Attempt to deliver one message
	async fn relay_mail (&self) -> Result<()> {
		if let Some(headers) = &self.headers {
			let mail = mail_parser::MessageParser::new().parse(&self.data)
				.context("Failed to parse mail.")?;

	/// # Returns
	/// * `Result<&ChatPeerId>` - Chat ID if found.
	///
	/// # Errors
	/// Returns an error if `name` is not configured.
	pub fn get (&self, name: &str) -> Result<&ChatPeerId> {
		self.recipients.get(&name.to_lowercase())
			.with_context(|| format!("Recipient {name:?} not found in configuration"))
	}

	/// Sends a text message to a specified chat.
	///
	/// # Arguments
	/// * `to` - Target chat ID.
	/// * `msg` - Message text (supports HTML formatting).

/// # Returns
/// * `Result<Cow<'a, str>>` - Escaped text or error if invalid.
///
/// # Errors
/// Returns an error if the text contains Telegram closing tags (`</pre>`, `</code>`).
pub fn validate <'a>(text: &'a str) -> Result<Cow<'a, str>> {
	if RE_CLOSING.is_match(text) {
		bail!("Text contains a Telegram closing tag (e.g., </pre>, </code>).");
	} else {
		Ok(encode_text(text))
}	}