pull: factor out interpolated progress

and add group/snapshot count info.

Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

src/backup/datastore.rs

@@ -759,3 +759,50 @@ impl DataStore {
         self.verify_new
     }
 }
+
+#[derive(Debug, Clone, Default)]
+/// Tracker for progress of operations iterating over `Datastore` contents.
+pub struct StoreProgress {
+    /// Completed groups
+    pub done_groups: u64,
+    /// Total groups
+    pub total_groups: u64,
+    /// Completed snapshots within current group
+    pub done_snapshots: u64,
+    /// Total snapshots in current group
+    pub group_snapshots: u64,
+}
+
+impl StoreProgress {
+    pub fn new(total_groups: u64) -> Self {
+        StoreProgress {
+            total_groups,
+            .. Default::default()
+        }
+    }
+
+    /// Calculates an interpolated relative progress based on current counters.
+    pub fn percentage(&self) -> f64 {
+        let per_groups = (self.done_groups as f64) / (self.total_groups as f64);
+        if self.group_snapshots == 0 {
+            per_groups
+        } else {
+            let per_snapshots = (self.done_snapshots as f64) / (self.group_snapshots as f64);
+            per_groups + (1.0 / self.total_groups as f64) * per_snapshots
+        }
+    }
+}
+
+impl std::fmt::Display for StoreProgress {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{:.2}% ({} of {} groups, {} of {} group snapshots)",
+            self.percentage() * 100.0,
+            self.done_groups,
+            self.total_groups,
+            self.done_snapshots,
+            self.group_snapshots,
+        )
+    }
+}