feat(core): workspace, Observation, content-derived id

tines-core/src/observation.rs

@@ -0,0 +1,125 @@
+//! Content-defined `Observation` identity.
+
+use crate::consts;
+use blake2::{Blake2s256, Digest};
+use heapless::Vec;
+use serde::{Deserialize, Serialize};
+
+/// 16-byte node identifier.
+pub type NodeId = [u8; 16];
+/// 16-byte content-derived observation identifier (first 16 bytes of Blake2s-256).
+pub type ObservationId = [u8; 16];
+/// Monotonic sequence number / tick.
+pub type Tick = u64;
+/// Heapless, fixed-capacity topic.
+pub type Topic = Vec<u8, { consts::MAX_TOPIC }>;
+/// Heapless, fixed-capacity payload.
+pub type Payload = Vec<u8, { consts::MAX_PAYLOAD }>;
+
+/// An observation published by a node, with content-derived identity.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Observation {
+    pub observer: NodeId,
+    pub seq: u64,
+    pub age_ms: u64,
+    pub observed_at: Option<u64>,
+    pub topic: Topic,
+    pub payload: Payload,
+}
+
+impl Observation {
+    /// Content-derived identity: Blake2s-256 over
+    /// `(observer, seq, topic_len, topic, payload_len, payload)`, first 16 bytes.
+    ///
+    /// The hash ignores `age_ms` and `observed_at`, so two observations that
+    /// differ only in age/time are still treated as the same key.
+    pub fn id(&self) -> ObservationId {
+        let mut hasher = Blake2s256::new();
+        hasher.update(self.observer);
+        hasher.update(self.seq.to_le_bytes());
+        hasher.update((self.topic.len() as u16).to_le_bytes());
+        hasher.update(&self.topic[..]);
+        hasher.update((self.payload.len() as u16).to_le_bytes());
+        hasher.update(&self.payload[..]);
+        let digest = hasher.finalize();
+        let mut id = [0u8; 16];
+        id.copy_from_slice(&digest[..16]);
+        id
+    }
+
+    /// Returns a copy with `age_ms` advanced by `elapsed_ms` (saturating).
+    pub fn aged(&self, elapsed_ms: u64) -> Observation {
+        Observation {
+            observer: self.observer,
+            seq: self.seq,
+            age_ms: self.age_ms.saturating_add(elapsed_ms),
+            observed_at: self.observed_at,
+            topic: self.topic.clone(),
+            payload: self.payload.clone(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn obs(seq: u64, age: u64, at: Option<u64>) -> Observation {
+        Observation {
+            observer: [1; 16],
+            seq,
+            age_ms: age,
+            observed_at: at,
+            topic: Topic::from_slice(b"door/3").unwrap(),
+            payload: Payload::from_slice(b"open").unwrap(),
+        }
+    }
+
+    #[test]
+    fn id_ignores_age_and_observed_at() {
+        assert_eq!(obs(1, 0, None).id(), obs(1, 999, Some(5)).id());
+    }
+
+    #[test]
+    fn id_changes_with_seq() {
+        assert_ne!(obs(1, 0, None).id(), obs(2, 0, None).id());
+    }
+
+    #[test]
+    fn id_changes_with_observer() {
+        let mut b = obs(1, 0, None);
+        b.observer = [2; 16];
+        assert_ne!(obs(1, 0, None).id(), b.id());
+    }
+
+    #[test]
+    fn id_distinguishes_topic_payload_boundary() {
+        // topic "ab" payload "c" vs topic "a" payload "bc" must differ
+        let mut x = obs(1, 0, None);
+        x.topic = Topic::from_slice(b"ab").unwrap();
+        x.payload = Payload::from_slice(b"c").unwrap();
+        let mut y = obs(1, 0, None);
+        y.topic = Topic::from_slice(b"a").unwrap();
+        y.payload = Payload::from_slice(b"bc").unwrap();
+        assert_ne!(x.id(), y.id());
+    }
+
+    #[test]
+    fn aged_saturates() {
+        assert_eq!(obs(1, u64::MAX - 1, None).aged(10).age_ms, u64::MAX);
+    }
+
+    #[test]
+    fn id_known_vector() {
+        // pin the hash layout: observer=[1;16], seq=7, topic="t", payload="p"
+        let mut o = obs(7, 0, None);
+        o.topic = Topic::from_slice(b"t").unwrap();
+        o.payload = Payload::from_slice(b"p").unwrap();
+        assert_eq!(
+            o.id(),
+            [
+                0x92, 0x37, 0x37, 0xa1, 0x06, 0x9b, 0xd9, 0x5e, 0x08, 0xc2, 0xe6, 0x39, 0x7d, 0x4a, 0x8f, 0xd0
+            ]
+        );
+    }
+}