feat(core): run bounded real gateway sessions

core/src/wire.rs

@@ -1,5 +1,6 @@
 use serde::de::DeserializeOwned;
 use serde::{Deserialize, Serialize};
+use std::time::{SystemTime, UNIX_EPOCH};
 
 use crate::error::{CoreError, Result};
 
@@ -126,6 +127,47 @@ struct Timestamp {
     nanosecond: u32,
 }
 
+pub(crate) fn now_utc() -> Result<String> {
+    system_time_utc(SystemTime::now())
+}
+
+fn system_time_utc(now: SystemTime) -> Result<String> {
+    let seconds = now
+        .duration_since(UNIX_EPOCH)
+        .map_err(|_| CoreError::InvalidArgument)?
+        .as_secs();
+    let days = seconds / 86_400;
+    let day_seconds = seconds % 86_400;
+    let shifted = days
+        .checked_add(719_468)
+        .ok_or(CoreError::InvalidArgument)?;
+    let era = shifted / 146_097;
+    let day_of_era = shifted % 146_097;
+    let year_of_era =
+        (day_of_era - day_of_era / 1_460 + day_of_era / 36_524 - day_of_era / 146_096) / 365;
+    let mut year = year_of_era + era * 400;
+    let day_of_year = day_of_era - (365 * year_of_era + year_of_era / 4 - year_of_era / 100);
+    let month_prime = (5 * day_of_year + 2) / 153;
+    let day = day_of_year - (153 * month_prime + 2) / 5 + 1;
+    let month = if month_prime < 10 {
+        month_prime + 3
+    } else {
+        month_prime - 9
+    };
+    if month <= 2 {
+        year += 1;
+    }
+    if year > 9_999 {
+        return Err(CoreError::InvalidArgument);
+    }
+    let hour = day_seconds / 3_600;
+    let minute = (day_seconds % 3_600) / 60;
+    let second = day_seconds % 60;
+    Ok(format!(
+        "{year:04}-{month:02}-{day:02}T{hour:02}:{minute:02}:{second:02}Z"
+    ))
+}
+
 fn timestamp(value: &str, exact_seconds: bool) -> Option<Timestamp> {
     let bytes = value.as_bytes();
     if bytes.len() < 20
@@ -452,6 +494,10 @@ impl ConnectionManifest {
         &self.gateway.public_identity
     }
 
+    pub(crate) fn features(&self) -> &[String] {
+        &self.tunnel.features
+    }
+
     pub(crate) fn admission(
         &self,
         client_nonce: String,
@@ -712,8 +758,21 @@ pub(crate) fn decode_stable_error(bytes: &[u8]) -> Result<DecodedStableError> {
 
 #[cfg(test)]
 mod stable_error_tests {
-    use super::decode_stable_error;
+    use super::{decode_stable_error, system_time_utc};
     use crate::error::CoreError;
+    use std::time::{Duration, UNIX_EPOCH};
+
+    #[test]
+    fn system_clock_conversion_is_exact_at_epoch_and_leap_day() {
+        assert_eq!(
+            system_time_utc(UNIX_EPOCH).as_deref(),
+            Ok("1970-01-01T00:00:00Z")
+        );
+        assert_eq!(
+            system_time_utc(UNIX_EPOCH + Duration::from_secs(1_709_251_199)).as_deref(),
+            Ok("2024-02-29T23:59:59Z")
+        );
+    }
 
     #[test]
     fn stable_error_uses_exact_rc5_bounds_and_preserves_retryability() {