From 2f42bc942cb124d8f8b05e1adb8a90a289cab9ba Mon Sep 17 00:00:00 2001
From: Alexis Sellier <self@cloudhead.io>
Date: Sun, 1 Jan 2023 22:29:40 +0100
Subject: [PATCH] cob: Make it easy to build histories

Signed-off-by: Alexis Sellier <self@cloudhead.io>
---
 radicle-cob/src/history.rs | 10 ++++--
 radicle-dag/src/lib.rs     | 39 ++++++++++++++++++++++
 radicle/src/cob.rs         |  3 ++
 radicle/src/cob/store.rs   |  2 +-
 radicle/src/cob/test.rs    | 67 ++++++++++++++++++++++++++++++++++++++
 5 files changed, 117 insertions(+), 4 deletions(-)
 create mode 100644 radicle/src/cob/test.rs

diff --git a/radicle-cob/src/history.rs b/radicle-cob/src/history.rs
index 4e534828..d2e6142f 100644
--- a/radicle-cob/src/history.rs
+++ b/radicle-cob/src/history.rs
@@ -38,7 +38,7 @@ pub enum CreateError {
 }
 
 impl History {
-    pub(crate) fn new_from_root<Id>(
+    pub fn new_from_root<Id>(
         id: Id,
         actor: PublicKey,
         resource: Oid,
@@ -114,14 +114,14 @@ impl History {
         pruning_fold::pruning_fold(init, items, f)
     }
 
-    pub(crate) fn tips(&self) -> BTreeSet<Oid> {
+    pub fn tips(&self) -> BTreeSet<Oid> {
         self.graph
             .tips()
             .map(|(_, entry)| (*entry.id()).into())
             .collect()
     }
 
-    pub(crate) fn extend<Id>(
+    pub fn extend<Id>(
         &mut self,
         new_id: Id,
         new_actor: PublicKey,
@@ -152,6 +152,10 @@ impl History {
             self.graph.dependency(new_id, (*tip).into());
         }
     }
+
+    pub fn merge(&mut self, other: Self) {
+        self.graph.merge(other.graph);
+    }
 }
 
 fn create_dag<'a>(root: &'a EntryId, entries: &'a HashMap<EntryId, EntryWithClock>) -> History {
diff --git a/radicle-dag/src/lib.rs b/radicle-dag/src/lib.rs
index fe2934b0..033318ff 100644
--- a/radicle-dag/src/lib.rs
+++ b/radicle-dag/src/lib.rs
@@ -130,6 +130,21 @@ impl<K: Eq + Copy + Hash, V> Dag<K, V> {
             .filter_map(|k| self.graph.get(k).map(|n| (k, n)))
     }
 
+    /// Merge a DAG into this one.
+    ///
+    /// If a key exists in both graphs, its value is set to that of the other graph.
+    pub fn merge(&mut self, other: Self) {
+        for k in other.tips.into_iter() {
+            self.tips.insert(k);
+        }
+        for k in other.roots.into_iter() {
+            self.roots.insert(k);
+        }
+        for (k, v) in other.graph.into_iter() {
+            self.graph.insert(k, v);
+        }
+    }
+
     /// Return a topological ordering of the graph's nodes, using the given RNG.
     /// Graphs with more than one partial order will return an arbitrary topological ordering.
     ///
@@ -238,6 +253,30 @@ mod tests {
         assert!(expected.contains(&sorted.as_slice()));
     }
 
+    #[test]
+    fn test_merge() {
+        let mut a = Dag::new();
+        let mut b = Dag::new();
+        let mut c = Dag::new();
+
+        a.node(0, ());
+        a.node(1, ());
+        a.dependency(1, 0);
+
+        b.node(0, ());
+        b.node(2, ());
+        b.dependency(2, 0);
+
+        c.merge(a);
+        c.merge(b);
+
+        assert!(c.get(&0).is_some());
+        assert!(c.get(&1).is_some());
+        assert!(c.get(&2).is_some());
+        assert!(c.has_dependency(&1, &0));
+        assert!(c.has_dependency(&2, &0));
+    }
+
     #[test]
     fn test_diamond() {
         let mut dag = Dag::new();
diff --git a/radicle/src/cob.rs b/radicle/src/cob.rs
index edee3642..4ce033ac 100644
--- a/radicle/src/cob.rs
+++ b/radicle/src/cob.rs
@@ -5,6 +5,9 @@ pub mod patch;
 pub mod store;
 pub mod thread;
 
+#[cfg(test)]
+pub mod test;
+
 pub use cob::{create, get, list, remove, update};
 pub use cob::{
     identity, object::collaboration::error, CollaborativeObject, Contents, Create, Entry, History,
diff --git a/radicle/src/cob/store.rs b/radicle/src/cob/store.rs
index cc1df74f..03630a1f 100644
--- a/radicle/src/cob/store.rs
+++ b/radicle/src/cob/store.rs
@@ -286,7 +286,7 @@ impl<T: FromHistory> Transaction<T> {
     }
 }
 
-mod encoding {
+pub mod encoding {
     use serde::Serialize;
 
     /// Serialize the change into a byte string.
diff --git a/radicle/src/cob/test.rs b/radicle/src/cob/test.rs
new file mode 100644
index 00000000..a76cd7a9
--- /dev/null
+++ b/radicle/src/cob/test.rs
@@ -0,0 +1,67 @@
+use std::marker::PhantomData;
+use std::ops::Deref;
+
+use nonempty::NonEmpty;
+use serde::Serialize;
+
+use crate::cob::op::Op;
+use crate::cob::store::encoding;
+use crate::cob::History;
+use crate::git::Oid;
+use crate::test::arbitrary;
+
+/// Convenience type for building histories.
+#[derive(Debug, Clone)]
+pub struct HistoryBuilder<A> {
+    history: History,
+    witness: PhantomData<A>,
+    resource: Oid,
+}
+
+impl<A: Serialize> HistoryBuilder<A> {
+    pub fn new(op: &Op<A>) -> HistoryBuilder<A> {
+        let entry = arbitrary::oid();
+        let resource = arbitrary::oid();
+        let contents = encoding::encode(&op.action).unwrap();
+
+        Self {
+            history: History::new_from_root(
+                entry,
+                op.author,
+                resource,
+                NonEmpty::new(contents),
+                op.timestamp.as_secs(),
+            ),
+            resource,
+            witness: PhantomData,
+        }
+    }
+
+    pub fn append(&mut self, op: &Op<A>) -> &mut Self {
+        self.history.extend(
+            arbitrary::oid(),
+            op.author,
+            self.resource,
+            NonEmpty::new(encoding::encode(&op.action).unwrap()),
+            op.timestamp.as_secs(),
+        );
+        self
+    }
+
+    pub fn merge(&mut self, other: Self) {
+        self.history.merge(other.history);
+    }
+}
+
+impl<A> Deref for HistoryBuilder<A> {
+    type Target = History;
+
+    fn deref(&self) -> &Self::Target {
+        &self.history
+    }
+}
+
+/// Create a new test history.
+pub fn history<A: Serialize>(op: &Op<A>) -> HistoryBuilder<A> {
+    HistoryBuilder::new(op)
+}