From 57fcb117fc3f87ac34e947862fc9f86de218689f Mon Sep 17 00:00:00 2001
From: Alexis Sellier <self@cloudhead.io>
Date: Wed, 28 Dec 2022 17:53:00 +0100
Subject: [PATCH] cob: Remove redundant history indices

Signed-off-by: Alexis Sellier <self@cloudhead.io>
---
 radicle-cob/src/history.rs | 16 ++++------------
 radicle-dag/src/lib.rs     | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/radicle-cob/src/history.rs b/radicle-cob/src/history.rs
index 7545a242..adf66ac0 100644
--- a/radicle-cob/src/history.rs
+++ b/radicle-cob/src/history.rs
@@ -21,7 +21,6 @@ pub use entry::{Clock, Contents, Entry, EntryId, EntryWithClock, Timestamp};
 #[derive(Clone, Debug)]
 pub struct History {
     graph: Dag<EntryId, EntryWithClock>,
-    indices: HashMap<EntryId, Oid>,
 }
 
 impl PartialEq for History {
@@ -150,30 +149,23 @@ impl History {
             },
         );
         for tip in tips {
-            let tip_ix = self.indices.get(&tip.into()).unwrap();
-            self.graph.dependency(new_id, (*tip_ix).into());
+            self.graph.dependency(new_id, (*tip).into());
         }
     }
 }
 
 fn create_dag<'a>(root: &'a EntryId, entries: &'a HashMap<EntryId, EntryWithClock>) -> History {
-    let mut graph: Dag<EntryId, EntryWithClock> = Dag::new();
-    let mut indices = HashMap::<EntryId, Oid>::new();
     let root_entry = entries.get(root).unwrap().clone();
-    graph.node(*root, root_entry.clone());
-    indices.insert(root_entry.id, (*root).into());
+    let mut graph: Dag<EntryId, EntryWithClock> = Dag::root(*root, root_entry.clone());
     let mut to_process = vec![root_entry];
 
     while let Some(entry) = to_process.pop() {
-        let entry_ix = indices[&entry.id];
-
         for child_id in entry.children() {
             let child = entries[child_id].clone();
             graph.node(*child_id, child.clone());
-            indices.insert(child.id, (*child_id).into());
-            graph.dependency(*child_id, entry_ix.into());
+            graph.dependency(*child_id, entry.id);
             to_process.push(child.clone());
         }
     }
-    History { graph, indices }
+    History { graph }
 }
diff --git a/radicle-dag/src/lib.rs b/radicle-dag/src/lib.rs
index 0fce13e4..fe2934b0 100644
--- a/radicle-dag/src/lib.rs
+++ b/radicle-dag/src/lib.rs
@@ -17,6 +17,16 @@ pub struct Node<K: Eq + Hash, V> {
     pub dependents: HashSet<K>,
 }
 
+impl<K: Eq + Hash, V> Node<K, V> {
+    fn new(value: V) -> Self {
+        Self {
+            value,
+            dependencies: HashSet::new(),
+            dependents: HashSet::new(),
+        }
+    }
+}
+
 impl<K: Eq + Hash, V> Borrow<V> for &Node<K, V> {
     fn borrow(&self) -> &V {
         &self.value
@@ -49,6 +59,14 @@ impl<K: Eq + Copy + Hash, V> Dag<K, V> {
         }
     }
 
+    pub fn root(key: K, value: V) -> Self {
+        Self {
+            graph: HashMap::from_iter([(key, Node::new(value))]),
+            tips: HashSet::from_iter([key]),
+            roots: HashSet::from_iter([key]),
+        }
+    }
+
     /// Check whether there are any nodes in the graph.
     pub fn is_empty(&self) -> bool {
         self.graph.is_empty()