BREAKING CHANGE(smtp-client): Replace the legacy TypeScript SMTP client with a new Rust-based SMTP client and IPC bridge for outbound delivery

rust/crates/mailer-smtp/src/client/error.rs

@@ -0,0 +1,160 @@
+//! SMTP client error types.
+
+use serde::Serialize;
+
+/// Errors that can occur during SMTP client operations.
+#[derive(Debug, thiserror::Error, Serialize)]
+pub enum SmtpClientError {
+    #[error("Connection error: {message}")]
+    ConnectionError { message: String },
+
+    #[error("Timeout: {message}")]
+    TimeoutError { message: String },
+
+    #[error("TLS error: {message}")]
+    TlsError { message: String },
+
+    #[error("Authentication failed: {message}")]
+    AuthenticationError { message: String },
+
+    #[error("Protocol error ({code}): {message}")]
+    ProtocolError { code: u16, message: String },
+
+    #[error("Pool exhausted: {message}")]
+    PoolExhausted { message: String },
+
+    #[error("Invalid configuration: {message}")]
+    ConfigError { message: String },
+}
+
+impl SmtpClientError {
+    /// Whether this error is retryable (temporary failure).
+    /// Permanent failures (5xx, auth failures) are not retryable.
+    pub fn is_retryable(&self) -> bool {
+        match self {
+            SmtpClientError::ConnectionError { .. } => true,
+            SmtpClientError::TimeoutError { .. } => true,
+            SmtpClientError::TlsError { .. } => false,
+            SmtpClientError::AuthenticationError { .. } => false,
+            SmtpClientError::ProtocolError { code, .. } => *code >= 400 && *code < 500,
+            SmtpClientError::PoolExhausted { .. } => true,
+            SmtpClientError::ConfigError { .. } => false,
+        }
+    }
+
+    /// The error type as a string for IPC serialization.
+    pub fn error_type(&self) -> &'static str {
+        match self {
+            SmtpClientError::ConnectionError { .. } => "connection",
+            SmtpClientError::TimeoutError { .. } => "timeout",
+            SmtpClientError::TlsError { .. } => "tls",
+            SmtpClientError::AuthenticationError { .. } => "authentication",
+            SmtpClientError::ProtocolError { .. } => "protocol",
+            SmtpClientError::PoolExhausted { .. } => "pool_exhausted",
+            SmtpClientError::ConfigError { .. } => "config",
+        }
+    }
+
+    /// The SMTP code if this is a protocol error.
+    pub fn smtp_code(&self) -> Option<u16> {
+        match self {
+            SmtpClientError::ProtocolError { code, .. } => Some(*code),
+            _ => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_retryable_errors() {
+        assert!(SmtpClientError::ConnectionError {
+            message: "refused".into()
+        }
+        .is_retryable());
+        assert!(SmtpClientError::TimeoutError {
+            message: "timed out".into()
+        }
+        .is_retryable());
+        assert!(SmtpClientError::PoolExhausted {
+            message: "full".into()
+        }
+        .is_retryable());
+        assert!(SmtpClientError::ProtocolError {
+            code: 421,
+            message: "try later".into()
+        }
+        .is_retryable());
+        assert!(SmtpClientError::ProtocolError {
+            code: 450,
+            message: "mailbox busy".into()
+        }
+        .is_retryable());
+    }
+
+    #[test]
+    fn test_non_retryable_errors() {
+        assert!(!SmtpClientError::AuthenticationError {
+            message: "bad creds".into()
+        }
+        .is_retryable());
+        assert!(!SmtpClientError::TlsError {
+            message: "cert invalid".into()
+        }
+        .is_retryable());
+        assert!(!SmtpClientError::ProtocolError {
+            code: 550,
+            message: "no such user".into()
+        }
+        .is_retryable());
+        assert!(!SmtpClientError::ProtocolError {
+            code: 554,
+            message: "rejected".into()
+        }
+        .is_retryable());
+        assert!(!SmtpClientError::ConfigError {
+            message: "bad config".into()
+        }
+        .is_retryable());
+    }
+
+    #[test]
+    fn test_error_type_strings() {
+        assert_eq!(
+            SmtpClientError::ConnectionError {
+                message: "x".into()
+            }
+            .error_type(),
+            "connection"
+        );
+        assert_eq!(
+            SmtpClientError::ProtocolError {
+                code: 550,
+                message: "x".into()
+            }
+            .error_type(),
+            "protocol"
+        );
+    }
+
+    #[test]
+    fn test_smtp_code() {
+        assert_eq!(
+            SmtpClientError::ProtocolError {
+                code: 550,
+                message: "x".into()
+            }
+            .smtp_code(),
+            Some(550)
+        );
+        assert_eq!(
+            SmtpClientError::ConnectionError {
+                message: "x".into()
+            }
+            .smtp_code(),
+            None
+        );
+    }
+}