Represent channels and messages using a split "History" and "Snapshot" model.

This separates the code that figures out what happened to an entity from the code that represents it to a user, and makes it easier to compute a snapshot at a point in time (for things like bootstrap). It also makes the internal logic a bit easier to follow, since it's easier to tell whether you're working with a point in time or with the whole recorded history.

This hefty.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/channel/history.rs b/src/channel/history.rs
new file mode 100644
index 0000000..3cc7d9d
--- /dev/null
+++ b/src/channel/history.rs
@@ -0,0 +1,42 @@
+use super::{
+    event::{Created, Deleted, Event},
+    Channel,
+};
+use crate::event::Instant;
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct History {
+    pub channel: Channel,
+    pub created: Instant,
+    pub deleted: Option<Instant>,
+}
+
+impl History {
+    fn created(&self) -> Event {
+        Event {
+            instant: self.created,
+            kind: Created {
+                channel: self.channel.clone(),
+            }
+            .into(),
+        }
+    }
+
+    fn deleted(&self) -> Option<Event> {
+        self.deleted.map(|instant| Event {
+            instant,
+            kind: Deleted {
+                channel: self.channel.id.clone(),
+            }
+            .into(),
+        })
+    }
+
+    pub fn events(&self) -> impl Iterator<Item = Event> {
+        [self.created()].into_iter().chain(self.deleted())
+    }
+
+    pub fn snapshot(&self) -> Channel {
+        self.channel.clone()
+    }
+}