1 files changed, 55 insertions, 0 deletions
diff --git a/src/vapid/history.rs b/src/vapid/history.rs
new file mode 100644
index 0000000..42f062b
--- /dev/null
+++ b/src/vapid/history.rs
@@ -0,0 +1,55 @@
+use p256::ecdsa::{SigningKey, VerifyingKey};
+use rand::thread_rng;
+
+use super::event::{Changed, Event};
+use crate::{clock::DateTime, event::Instant};
+
+#[derive(Debug)]
+pub struct History {
+    pub key: VerifyingKey,
+    pub changed: Instant,
+}
+
+// Lifecycle interface
+impl History {
+    pub fn begin(changed: &Instant) -> (Self, SigningKey) {
+        let key = SigningKey::random(&mut thread_rng());
+        (
+            Self {
+                key: VerifyingKey::from(&key),
+                changed: *changed,
+            },
+            key,
+        )
+    }
+
+    // `self` _is_ unused here, clippy is right about that. This choice is deliberate, however - it
+    // makes it harder to inadvertently reuse a rotated key via its history, and it makes the
+    // lifecycle interface more obviously consistent between this and other History types.
+    #[allow(clippy::unused_self)]
+    pub fn rotate(self, changed: &Instant) -> (Self, SigningKey) {
+        Self::begin(changed)
+    }
+}
+
+// State interface
+impl History {
+    pub fn older_than(&self, when: DateTime) -> bool {
+        self.changed.at < when
+    }
+}
+
+// Events interface
+impl History {
+    pub fn events(&self) -> impl Iterator<Item = Event> + Clone {
+        [self.changed()].into_iter()
+    }
+
+    fn changed(&self) -> Event {
+        Changed {
+            key: self.key,
+            instant: self.changed,
+        }
+        .into()
+    }
+}