Add helper functions for invoice expiry

diff --git a/lightning-invoice/src/lib.rs b/lightning-invoice/src/lib.rs
index 37c74922ee6957fcb1a0211808e6e13a62f18fac..2f49cf5d0b3a44cc91a1a83071e43059551f63ea 100644 (file)
--- a/lightning-invoice/src/lib.rs
+++ b/lightning-invoice/src/lib.rs
@@ -1213,6 +1213,12 @@ impl Invoice {
                self.signed_invoice.recover_payee_pub_key().expect("was checked by constructor").0
        }
 
+       /// Returns the Duration since the Unix epoch at which the invoice expires.
+       /// Returning None if overflow occurred.
+       pub fn expires_at(&self) -> Option<Duration> {
+               self.duration_since_epoch().checked_add(self.expiry_time())
+       }
+
        /// Returns the invoice's expiry time, if present, otherwise [`DEFAULT_EXPIRY_TIME`].
        pub fn expiry_time(&self) -> Duration {
                self.signed_invoice.expiry_time()
@@ -1235,6 +1241,20 @@ impl Invoice {
                }
        }
 
+       /// Returns the Duration remaining until the invoice expires.
+       #[cfg(feature = "std")]
+       pub fn duration_until_expiry(&self) -> Duration {
+               SystemTime::now().duration_since(SystemTime::UNIX_EPOCH)
+                       .map(|now| self.expiration_remaining_from_epoch(now))
+                       .unwrap_or(Duration::from_nanos(0))
+       }
+
+       /// Returns the Duration remaining until the invoice expires given the current time.
+       /// `time` is the timestamp as a duration since the Unix epoch.
+       pub fn expiration_remaining_from_epoch(&self, time: Duration) -> Duration {
+               self.expires_at().map(|x| x.checked_sub(time)).flatten().unwrap_or(Duration::from_nanos(0))
+       }
+
        /// Returns whether the expiry time would pass at the given point in time.
        /// `at_time` is the timestamp as a duration since the Unix epoch.
        pub fn would_expire(&self, at_time: Duration) -> bool {