crdt: Small improvements

Signed-off-by: Alexis Sellier <alexis@radicle.xyz>

radicle-crdt/src/change.rs

@@ -100,13 +100,14 @@ impl<G: Signer, A: Clone + Serialize> Actor<G, A> {
     /// Create a new change.
     pub fn change(&mut self, action: A) -> Change<A> {
         let author = *self.signer.public_key();
-        let clock = self.clock.tick();
+        let clock = self.clock;
         let change = Change {
             action,
             author,
             clock,
         };
         self.changes.insert((self.clock, author), change.clone());
+        self.clock.tick();
 
         change
     }

radicle-crdt/src/clock.rs

@@ -29,6 +29,11 @@ impl Lamport {
         self.counter.merge(other.counter);
         self.tick()
     }
+
+    /// Reset clock to default state.
+    pub fn reset(&mut self) {
+        self.counter = Max::default();
+    }
 }
 
 impl From<u64> for Lamport {

radicle-crdt/src/lwwmap.rs

@@ -2,11 +2,14 @@ use std::collections::btree_map::Entry;
 use std::collections::BTreeMap;
 
 use crate::lwwreg::LWWReg;
-use crate::Semilattice;
+use crate::{clock, Semilattice};
 
 /// Last-Write-Wins Map.
+///
+/// In case a value is added and removed under a key at the same time,
+/// the "add" takes precedence over the "remove".
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub struct LWWMap<K, V, C> {
+pub struct LWWMap<K, V, C = clock::Lamport> {
     inner: BTreeMap<K, LWWReg<Option<V>, C>>,
 }
 

radicle-crdt/src/lwwset.rs

@@ -2,6 +2,9 @@ use crate::clock;
 use crate::{lwwmap::LWWMap, Semilattice};
 
 /// Last-Write-Wins Set.
+///
+/// In case the same value is added and removed at the same time,
+/// the "add" takes precedence over the "remove".
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct LWWSet<T, C = clock::Lamport> {
     inner: LWWMap<T, (), C>,
@@ -129,6 +132,14 @@ mod tests {
         set.remove('a', 2);
         assert!(!set.contains(&'a'));
         assert!(!set.iter().any(|c| *c == 'a'));
+
+        set.insert('b', 3);
+        set.remove('b', 3);
+        assert!(set.contains(&'b')); // Insert precedence.
+
+        set.remove('c', 3);
+        set.insert('c', 3);
+        assert!(set.contains(&'c')); // Insert precedence.
     }
 
     #[test]