From 5c0505e221eb96028d1a92566832cb59d580507d Mon Sep 17 00:00:00 2001
From: Alexis Sellier <self@cloudhead.io>
Date: Mon, 27 Feb 2023 11:27:15 +0100
Subject: [PATCH] crdt: Implement `GSet` type, based on `GMap`

---
 radicle-crdt/src/gmap.rs |  8 +++-
 radicle-crdt/src/gset.rs | 97 ++++++++++++++++++++++++++++++++++++++++
 radicle-crdt/src/lib.rs  |  2 +
 3 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100644 radicle-crdt/src/gset.rs

diff --git a/radicle-crdt/src/gmap.rs b/radicle-crdt/src/gmap.rs
index 42d750a2..9377ec00 100644
--- a/radicle-crdt/src/gmap.rs
+++ b/radicle-crdt/src/gmap.rs
@@ -1,4 +1,4 @@
-use std::collections::btree_map::{Entry, IntoIter};
+use std::collections::btree_map::{Entry, IntoIter, IntoKeys};
 use std::collections::BTreeMap;
 use std::ops::Deref;
 
@@ -35,6 +35,12 @@ impl<K: Ord, V: Semilattice> GMap<K, V> {
     }
 }
 
+impl<K, V> GMap<K, V> {
+    pub fn into_keys(self) -> IntoKeys<K, V> {
+        self.inner.into_keys()
+    }
+}
+
 impl<K: Ord, V: Semilattice> FromIterator<(K, V)> for GMap<K, V> {
     fn from_iter<I: IntoIterator<Item = (K, V)>>(iter: I) -> Self {
         let mut map = GMap::default();
diff --git a/radicle-crdt/src/gset.rs b/radicle-crdt/src/gset.rs
new file mode 100644
index 00000000..4a4c0975
--- /dev/null
+++ b/radicle-crdt/src/gset.rs
@@ -0,0 +1,97 @@
+use std::collections::btree_map::{IntoKeys, Keys};
+use std::ops::Deref;
+
+use crate::GMap;
+use crate::Semilattice;
+
+/// Grow-only set.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct GSet<K> {
+    inner: GMap<K, ()>,
+}
+
+impl<K: Ord> GSet<K> {
+    pub fn singleton(key: K) -> Self {
+        Self {
+            inner: GMap::from_iter([(key, ())]),
+        }
+    }
+
+    pub fn insert(&mut self, key: K) {
+        self.inner.insert(key, ());
+    }
+
+    pub fn iter(&self) -> Keys<'_, K, ()> {
+        self.inner.keys()
+    }
+}
+
+impl<K: Ord> FromIterator<K> for GSet<K> {
+    fn from_iter<I: IntoIterator<Item = K>>(iter: I) -> Self {
+        let mut map = GSet::default();
+        for k in iter.into_iter() {
+            map.insert(k);
+        }
+        map
+    }
+}
+
+impl<K: Ord> Extend<K> for GSet<K> {
+    fn extend<I: IntoIterator<Item = K>>(&mut self, iter: I) {
+        for k in iter.into_iter() {
+            self.insert(k);
+        }
+    }
+}
+
+impl<K> IntoIterator for GSet<K> {
+    type Item = K;
+    type IntoIter = IntoKeys<K, ()>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.into_keys()
+    }
+}
+
+impl<K> Default for GSet<K> {
+    fn default() -> Self {
+        Self {
+            inner: GMap::default(),
+        }
+    }
+}
+
+impl<K: Ord> Semilattice for GSet<K> {
+    fn merge(&mut self, other: Self) {
+        for k in other.into_iter() {
+            self.insert(k);
+        }
+    }
+}
+
+impl<K> Deref for GSet<K> {
+    type Target = GMap<K, ()>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.inner
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use qcheck_macros::quickcheck;
+
+    use super::*;
+
+    #[quickcheck]
+    fn prop_semilattice(a: Vec<u8>, b: Vec<u8>, c: Vec<u8>, mix: Vec<u8>) {
+        let mut a = GSet::from_iter(a);
+        let mut b = GSet::from_iter(b);
+        let c = GSet::from_iter(c);
+
+        a.extend(mix.clone());
+        b.extend(mix);
+
+        crate::test::assert_laws(&a, &b, &c);
+    }
+}
diff --git a/radicle-crdt/src/lib.rs b/radicle-crdt/src/lib.rs
index 930984fa..1595dbd0 100644
--- a/radicle-crdt/src/lib.rs
+++ b/radicle-crdt/src/lib.rs
@@ -4,6 +4,7 @@
 #![allow(clippy::type_complexity)]
 pub mod clock;
 pub mod gmap;
+pub mod gset;
 pub mod lwwmap;
 pub mod lwwreg;
 pub mod lwwset;
@@ -17,6 +18,7 @@ pub mod test;
 
 pub use clock::Lamport;
 pub use gmap::GMap;
+pub use gset::GSet;
 pub use lwwmap::LWWMap;
 pub use lwwreg::LWWReg;
 pub use lwwset::LWWSet;