1 files changed, 60 insertions, 0 deletions
diff --git a/aero-collections/src/mail/snapshot.rs b/aero-collections/src/mail/snapshot.rs
new file mode 100644
index 0000000..6f8a8a8
--- /dev/null
+++ b/aero-collections/src/mail/snapshot.rs
@@ -0,0 +1,60 @@
+use std::sync::Arc;
+
+use anyhow::Result;
+
+use super::mailbox::Mailbox;
+use super::query::{Query, QueryScope};
+use super::uidindex::UidIndex;
+use crate::unique_ident::UniqueIdent;
+
+/// A Frozen Mailbox has a snapshot of the current mailbox
+/// state that is desynchronized with the real mailbox state.
+/// It's up to the user to choose when their snapshot must be updated
+/// to give useful information to their clients
+pub struct FrozenMailbox {
+    pub mailbox: Arc<Mailbox>,
+    pub snapshot: UidIndex,
+}
+
+impl FrozenMailbox {
+    /// Create a snapshot from a mailbox, the mailbox + the snapshot
+    /// becomes the "Frozen Mailbox".
+    pub async fn new(mailbox: Arc<Mailbox>) -> Self {
+        let state = mailbox.current_uid_index().await;
+
+        Self {
+            mailbox,
+            snapshot: state,
+        }
+    }
+
+    /// Force the synchronization of the inner mailbox
+    /// but do not update the local snapshot
+    pub async fn sync(&self) -> Result<()> {
+        self.mailbox.opportunistic_sync().await
+    }
+
+    /// Peek snapshot without updating the frozen mailbox
+    /// Can be useful if you want to plan some writes
+    /// while sending a diff to the client later
+    pub async fn peek(&self) -> UidIndex {
+        self.mailbox.current_uid_index().await
+    }
+
+    /// Update the FrozenMailbox local snapshot.
+    /// Returns the old snapshot, so you can build a diff
+    pub async fn update(&mut self) -> UidIndex {
+        let old_snapshot = self.snapshot.clone();
+        self.snapshot = self.mailbox.current_uid_index().await;
+
+        old_snapshot
+    }
+
+    pub fn query<'a, 'b>(&'a self, uuids: &'b [UniqueIdent], scope: QueryScope) -> Query<'a, 'b> {
+        Query {
+            frozen: self,
+            emails: uuids,
+            scope,
+        }
+    }
+}