cob: Include commit timestamp in `Entry`

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

radicle-cob/src/backend/git/change.rs

@@ -9,6 +9,7 @@ use git_commit::{self as commit, Commit};
 use git_ext::Oid;
 use git_trailers::OwnedTrailer;
 
+use crate::history::entry::Timestamp;
 use crate::{
     change::{self, store, Change},
     history::entry,
@@ -114,7 +115,7 @@ impl change::Storage for git2::Repository {
             Signature::from((*key, sig))
         };
 
-        let id = write_commit(self, resource, tips, message, signature.clone(), tree)?;
+        let (id, timestamp) = write_commit(self, resource, tips, message, signature.clone(), tree)?;
         Ok(Change {
             id,
             revision: revision.into(),
@@ -122,11 +123,13 @@ impl change::Storage for git2::Repository {
             resource,
             manifest,
             contents,
+            timestamp,
         })
     }
 
     fn load(&self, id: Self::ObjectId) -> Result<Change, Self::LoadError> {
         let commit = Commit::read(self, id.into())?;
+        let timestamp = git2::Time::from(commit.committer().time).seconds() as u64;
         let resource = parse_resource_trailer(commit.trailers())?;
         let mut signatures = Signatures::try_from(&commit)?
             .into_iter()
@@ -149,6 +152,7 @@ impl change::Storage for git2::Repository {
             resource,
             manifest,
             contents,
+            timestamp,
         })
     }
 }
@@ -208,7 +212,7 @@ fn write_commit<O>(
     message: String,
     signature: Signature,
     tree: git2::Tree,
-) -> Result<Oid, error::Create>
+) -> Result<(Oid, Timestamp), error::Create>
 where
     O: AsRef<git2::Oid>,
 {
@@ -221,14 +225,14 @@ where
 
     {
         let author = repo.signature()?;
+        let timestamp = author.when().seconds() as Timestamp;
         let mut headers = commit::Headers::new();
         headers.push(
             "gpgsig",
             &String::from_utf8(crypto::ssh::ExtendedSignature::from(signature).to_armored())?,
         );
         let author = commit::Author::try_from(&author)?;
-
-        let commit = Commit::new(
+        let oid = Commit::new(
             tree.id(),
             parents,
             author.clone(),
@@ -236,11 +240,10 @@ where
             headers,
             message,
             trailers,
-        );
-        commit
-            .write(repo)
-            .map(Oid::from)
-            .map_err(error::Create::from)
+        )
+        .write(repo)?;
+
+        Ok((Oid::from(oid), timestamp))
     }
 }
 

radicle-cob/src/change/store.rs

@@ -7,7 +7,10 @@ use std::{error::Error, fmt};
 
 use serde::{Deserialize, Serialize};
 
-use crate::{history::Contents, signatures, TypeName};
+use crate::{
+    history::{Contents, Timestamp},
+    signatures, TypeName,
+};
 
 pub trait Storage {
     type CreateError: Error + Send + Sync + 'static;
@@ -59,6 +62,8 @@ pub struct Change<Resource, Id, Signature> {
     pub manifest: Manifest,
     /// The contents that describe `Change`.
     pub contents: Contents,
+    /// Timestamp of change.
+    pub timestamp: Timestamp,
 }
 
 impl<Resource, Id, S> fmt::Display for Change<Resource, Id, S>

radicle-cob/src/change_graph/evaluation.rs

@@ -70,6 +70,7 @@ fn evaluate_change(
         change.resource,
         child_commits.iter().cloned(),
         change.contents().clone(),
+        change.timestamp,
     ))
 }
 

radicle-cob/src/history.rs

@@ -15,7 +15,7 @@ use radicle_crypto::PublicKey;
 use crate::pruning_fold;
 
 pub mod entry;
-pub use entry::{Clock, Contents, Entry, EntryId, EntryWithClock};
+pub use entry::{Clock, Contents, Entry, EntryId, EntryWithClock, Timestamp};
 
 /// The DAG of changes making up the history of a collaborative object.
 #[derive(Clone, Debug)]
@@ -44,6 +44,7 @@ impl History {
         actor: PublicKey,
         resource: Oid,
         contents: Contents,
+        timestamp: Timestamp,
     ) -> Self
     where
         Id: Into<EntryId>,
@@ -55,6 +56,7 @@ impl History {
             resource,
             children: vec![],
             contents,
+            timestamp,
         };
         let mut entries = HashMap::new();
         entries.insert(id, EntryWithClock::from(root_entry));
@@ -85,6 +87,16 @@ impl History {
             .unwrap_or_default()
     }
 
+    /// Get the current history timestamp.
+    /// This is the latest timestamp of any tip.
+    pub fn timestamp(&self) -> Clock {
+        self.graph
+            .externals(petgraph::Direction::Outgoing)
+            .map(|n| self.graph[n].timestamp())
+            .max()
+            .unwrap_or_default()
+    }
+
     /// A topological (parents before children) traversal of the dependency
     /// graph of this history. This is analagous to
     /// [`std::iter::Iterator::fold`] in that it folds every change into an
@@ -120,6 +132,7 @@ impl History {
         new_actor: PublicKey,
         new_resource: Oid,
         new_contents: Contents,
+        new_timestamp: Timestamp,
     ) where
         Id: Into<EntryId>,
     {
@@ -131,6 +144,7 @@ impl History {
             new_resource,
             std::iter::empty::<git2::Oid>(),
             new_contents,
+            new_timestamp,
         );
         let new_ix = self.graph.add_node(EntryWithClock {
             entry: new_entry,

radicle-cob/src/history/entry.rs

@@ -16,6 +16,9 @@ pub type Contents = Vec<u8>;
 /// Logical clock used to track causality in change graph.
 pub type Clock = u64;
 
+/// Local time in seconds since epoch.
+pub type Timestamp = u64;
+
 /// A unique identifier for a history entry.
 #[derive(Clone, Copy, Debug, PartialEq, Hash, Eq, PartialOrd, Ord)]
 pub struct EntryId(Oid);
@@ -51,6 +54,8 @@ pub struct Entry {
     pub(super) children: Vec<EntryId>,
     /// The contents of this entry.
     pub(super) contents: Contents,
+    /// The entry timestamp, as seconds since epoch.
+    pub(super) timestamp: Timestamp,
 }
 
 impl Entry {
@@ -60,6 +65,7 @@ impl Entry {
         resource: Oid,
         children: ChildIds,
         contents: Contents,
+        timestamp: Timestamp,
     ) -> Self
     where
         Id1: Into<EntryId>,
@@ -72,6 +78,7 @@ impl Entry {
             resource,
             children: children.into_iter().map(|id| id.into()).collect(),
             contents,
+            timestamp,
         }
     }
 
@@ -90,6 +97,11 @@ impl Entry {
         &self.actor
     }
 
+    /// The entry timestamp.
+    pub fn timestamp(&self) -> Timestamp {
+        self.timestamp
+    }
+
     /// The contents of this change
     pub fn contents(&self) -> &Contents {
         &self.contents

radicle-cob/src/object/collaboration/create.rs

@@ -76,6 +76,7 @@ where
         init_change.signature.key,
         resource.content_id(),
         contents.clone(),
+        init_change.timestamp,
     );
 
     let object_id = init_change.id().into();

radicle-cob/src/object/collaboration/update.rs

@@ -81,9 +81,13 @@ where
             message,
         },
     )?;
-    object
-        .history
-        .extend(change.id, change.signature.key, change.resource, changes);
+    object.history.extend(
+        change.id,
+        change.signature.key,
+        change.resource,
+        changes,
+        change.timestamp,
+    );
     storage
         .update(identifier, typename, &object_id, &change)
         .map_err(|err| error::Update::Refs { err: Box::new(err) })?;