//! UDP error classification shared by Dosh clients, servers, and embedders.

pub fn is_transient_udp_error(err: &std::io::Error) -> bool {
    matches!(
        err.kind(),
        std::io::ErrorKind::Interrupted
            | std::io::ErrorKind::TimedOut
            | std::io::ErrorKind::WouldBlock
    ) || err.raw_os_error().is_some_and(is_transient_udp_os_error)
}

pub fn is_transient_udp_send_error(err: &std::io::Error) -> bool {
    is_transient_udp_error(err)
}

#[cfg(unix)]
fn is_transient_udp_os_error(code: i32) -> bool {
    matches!(
        code,
        libc::EADDRNOTAVAIL
            | libc::ECONNREFUSED
            | libc::ECONNRESET
            | libc::EHOSTDOWN
            | libc::EHOSTUNREACH
            | libc::ENETDOWN
            | libc::ENETRESET
            | libc::ENETUNREACH
            | libc::ETIMEDOUT
    )
}

#[cfg(windows)]
fn is_transient_udp_os_error(code: i32) -> bool {
    matches!(
        code,
        10049  // WSAEADDRNOTAVAIL
            | 10050 // WSAENETDOWN
            | 10051 // WSAENETUNREACH
            | 10052 // WSAENETRESET
            | 10054 // WSAECONNRESET
            | 10060 // WSAETIMEDOUT
            | 10061 // WSAECONNREFUSED
            | 10064 // WSAEHOSTDOWN
            | 10065 // WSAEHOSTUNREACH
    )
}

#[cfg(not(any(unix, windows)))]
fn is_transient_udp_os_error(_code: i32) -> bool {
    false
}

#[cfg(test)]
mod tests {
    use super::{is_transient_udp_error, is_transient_udp_send_error};

    #[test]
    fn classifies_portable_transient_udp_errors() {
        for kind in [
            std::io::ErrorKind::Interrupted,
            std::io::ErrorKind::TimedOut,
            std::io::ErrorKind::WouldBlock,
        ] {
            let err = std::io::Error::from(kind);
            assert!(is_transient_udp_error(&err));
            assert!(is_transient_udp_send_error(&err));
        }
        let fatal = std::io::Error::from(std::io::ErrorKind::PermissionDenied);
        assert!(!is_transient_udp_error(&fatal));
        assert!(!is_transient_udp_send_error(&fatal));
    }

    #[cfg(unix)]
    #[test]
    fn classifies_unix_network_churn_as_transient() {
        for code in [
            libc::EADDRNOTAVAIL,
            libc::ECONNREFUSED,
            libc::ECONNRESET,
            libc::EHOSTDOWN,
            libc::EHOSTUNREACH,
            libc::ENETDOWN,
            libc::ENETRESET,
            libc::ENETUNREACH,
            libc::ETIMEDOUT,
        ] {
            let err = std::io::Error::from_raw_os_error(code);
            assert!(is_transient_udp_error(&err));
            assert!(is_transient_udp_send_error(&err));
        }
    }

    #[cfg(windows)]
    #[test]
    fn classifies_windows_network_churn_as_transient() {
        for code in [
            10049, 10050, 10051, 10052, 10054, 10060, 10061, 10064, 10065,
        ] {
            let err = std::io::Error::from_raw_os_error(code);
            assert!(is_transient_udp_error(&err));
            assert!(is_transient_udp_send_error(&err));
        }
    }
}