feat(mailer-smtp): implement in-process SMTP server and management IPC integration
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284
rust/crates/mailer-smtp/src/response.rs
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284
rust/crates/mailer-smtp/src/response.rs
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//! SMTP response builder.
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//!
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//! Constructs properly formatted SMTP response lines with status codes,
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//! multiline support, and EHLO capability advertisement.
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use serde::{Deserialize, Serialize};
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/// An SMTP response to send to the client.
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#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
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pub struct SmtpResponse {
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/// 3-digit SMTP status code.
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pub code: u16,
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/// Response lines (without the status code prefix).
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pub lines: Vec<String>,
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}
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impl SmtpResponse {
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/// Create a single-line response.
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pub fn new(code: u16, message: impl Into<String>) -> Self {
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Self {
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code,
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lines: vec![message.into()],
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}
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}
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/// Create a multiline response.
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pub fn multiline(code: u16, lines: Vec<String>) -> Self {
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Self { code, lines }
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}
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/// Format the response as bytes ready to write to the socket.
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///
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/// Multiline responses use `code-text` for intermediate lines
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/// and `code text` for the final line (RFC 5321 §4.2).
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pub fn to_bytes(&self) -> Vec<u8> {
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let mut buf = Vec::new();
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if self.lines.is_empty() {
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buf.extend_from_slice(format!("{} \r\n", self.code).as_bytes());
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} else if self.lines.len() == 1 {
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buf.extend_from_slice(
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format!("{} {}\r\n", self.code, self.lines[0]).as_bytes(),
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);
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} else {
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for (i, line) in self.lines.iter().enumerate() {
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if i < self.lines.len() - 1 {
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buf.extend_from_slice(
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format!("{}-{}\r\n", self.code, line).as_bytes(),
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);
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} else {
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buf.extend_from_slice(
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format!("{} {}\r\n", self.code, line).as_bytes(),
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);
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}
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}
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}
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buf
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}
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// --- Common response constructors ---
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/// 220 Service ready greeting.
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pub fn greeting(hostname: &str) -> Self {
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Self::new(220, format!("{hostname} ESMTP Service Ready"))
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}
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/// 221 Service closing.
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pub fn closing(hostname: &str) -> Self {
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Self::new(221, format!("{hostname} Service closing transmission channel"))
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}
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/// 250 OK.
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pub fn ok(message: impl Into<String>) -> Self {
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Self::new(250, message)
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}
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/// EHLO response with capabilities.
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pub fn ehlo_response(hostname: &str, capabilities: &[String]) -> Self {
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let mut lines = Vec::with_capacity(capabilities.len() + 1);
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lines.push(format!("{hostname} greets you"));
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for cap in capabilities {
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lines.push(cap.clone());
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}
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Self::multiline(250, lines)
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}
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/// 235 Authentication successful.
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pub fn auth_success() -> Self {
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Self::new(235, "2.7.0 Authentication successful")
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}
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/// 334 Auth challenge (base64-encoded prompt).
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pub fn auth_challenge(prompt: &str) -> Self {
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Self::new(334, prompt)
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}
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/// 354 Start mail input.
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pub fn start_data() -> Self {
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Self::new(354, "Start mail input; end with <CRLF>.<CRLF>")
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}
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/// 421 Service not available.
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pub fn service_unavailable(hostname: &str, reason: &str) -> Self {
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Self::new(421, format!("{hostname} {reason}"))
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}
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/// 450 Temporary failure.
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pub fn temp_failure(message: impl Into<String>) -> Self {
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Self::new(450, message)
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}
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/// 451 Local error.
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pub fn local_error(message: impl Into<String>) -> Self {
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Self::new(451, message)
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}
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/// 500 Syntax error.
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pub fn syntax_error() -> Self {
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Self::new(500, "Syntax error, command unrecognized")
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}
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/// 501 Syntax error in parameters.
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pub fn param_error(message: impl Into<String>) -> Self {
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Self::new(501, message)
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}
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/// 502 Command not implemented.
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pub fn not_implemented() -> Self {
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Self::new(502, "Command not implemented")
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}
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/// 503 Bad sequence.
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pub fn bad_sequence(message: impl Into<String>) -> Self {
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Self::new(503, message)
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}
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/// 530 Authentication required.
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pub fn auth_required() -> Self {
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Self::new(530, "5.7.0 Authentication required")
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}
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/// 535 Authentication failed.
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pub fn auth_failed() -> Self {
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Self::new(535, "5.7.8 Authentication credentials invalid")
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}
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/// 550 Mailbox unavailable.
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pub fn mailbox_unavailable(message: impl Into<String>) -> Self {
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Self::new(550, message)
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}
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/// 552 Message size exceeded.
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pub fn size_exceeded(max_size: u64) -> Self {
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Self::new(
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552,
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format!("5.3.4 Message size exceeds maximum of {max_size} bytes"),
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)
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}
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/// 554 Transaction failed.
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pub fn transaction_failed(message: impl Into<String>) -> Self {
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Self::new(554, message)
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}
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/// Check if this is a success response (2xx).
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pub fn is_success(&self) -> bool {
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self.code >= 200 && self.code < 300
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}
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/// Check if this is a temporary error (4xx).
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pub fn is_temp_error(&self) -> bool {
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self.code >= 400 && self.code < 500
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}
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/// Check if this is a permanent error (5xx).
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pub fn is_perm_error(&self) -> bool {
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self.code >= 500 && self.code < 600
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}
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}
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/// Build the list of EHLO capabilities for the server.
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pub fn build_capabilities(
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max_size: u64,
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tls_available: bool,
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already_secure: bool,
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auth_available: bool,
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) -> Vec<String> {
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let mut caps = vec![
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format!("SIZE {max_size}"),
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"8BITMIME".to_string(),
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"PIPELINING".to_string(),
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"ENHANCEDSTATUSCODES".to_string(),
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"HELP".to_string(),
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];
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// Only advertise STARTTLS if TLS is available and not already using TLS
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if tls_available && !already_secure {
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caps.push("STARTTLS".to_string());
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}
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if auth_available {
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caps.push("AUTH PLAIN LOGIN".to_string());
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}
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caps
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_single_line() {
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let resp = SmtpResponse::new(250, "OK");
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assert_eq!(resp.to_bytes(), b"250 OK\r\n");
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}
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#[test]
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fn test_multiline() {
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let resp = SmtpResponse::multiline(
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250,
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vec![
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"mail.example.com greets you".into(),
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"SIZE 10485760".into(),
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"STARTTLS".into(),
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],
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);
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let expected = b"250-mail.example.com greets you\r\n250-SIZE 10485760\r\n250 STARTTLS\r\n";
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assert_eq!(resp.to_bytes(), expected.to_vec());
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}
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#[test]
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fn test_greeting() {
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let resp = SmtpResponse::greeting("mail.example.com");
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assert_eq!(resp.code, 220);
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assert!(resp.lines[0].contains("mail.example.com"));
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}
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#[test]
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fn test_ehlo_response() {
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let caps = vec!["SIZE 10485760".into(), "STARTTLS".into()];
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let resp = SmtpResponse::ehlo_response("mail.example.com", &caps);
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assert_eq!(resp.code, 250);
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assert_eq!(resp.lines.len(), 3); // hostname + 2 caps
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}
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#[test]
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fn test_status_checks() {
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assert!(SmtpResponse::new(250, "OK").is_success());
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assert!(SmtpResponse::new(450, "Try later").is_temp_error());
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assert!(SmtpResponse::new(550, "No such user").is_perm_error());
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assert!(!SmtpResponse::new(250, "OK").is_temp_error());
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}
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#[test]
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fn test_build_capabilities() {
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let caps = build_capabilities(10485760, true, false, true);
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assert!(caps.contains(&"SIZE 10485760".to_string()));
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assert!(caps.contains(&"STARTTLS".to_string()));
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assert!(caps.contains(&"AUTH PLAIN LOGIN".to_string()));
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assert!(caps.contains(&"PIPELINING".to_string()));
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}
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#[test]
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fn test_build_capabilities_secure() {
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// When already secure, STARTTLS should NOT be advertised
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let caps = build_capabilities(10485760, true, true, false);
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assert!(!caps.contains(&"STARTTLS".to_string()));
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assert!(!caps.contains(&"AUTH PLAIN LOGIN".to_string()));
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}
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#[test]
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fn test_empty_response() {
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let resp = SmtpResponse::multiline(250, vec![]);
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assert_eq!(resp.to_bytes(), b"250 \r\n");
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}
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#[test]
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fn test_common_responses() {
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assert_eq!(SmtpResponse::start_data().code, 354);
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assert_eq!(SmtpResponse::syntax_error().code, 500);
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assert_eq!(SmtpResponse::not_implemented().code, 502);
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assert_eq!(SmtpResponse::bad_sequence("test").code, 503);
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assert_eq!(SmtpResponse::auth_required().code, 530);
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assert_eq!(SmtpResponse::auth_failed().code, 535);
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assert_eq!(SmtpResponse::auth_success().code, 235);
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}
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}
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