From 76cf9022173d5764814544082f2b518a9df1934b Mon Sep 17 00:00:00 2001
From: cc <cc7@duck.com>
Date: Thu, 22 Oct 2026 15:09:27 -0700
Subject: [PATCH] Support atomic insertion of transform batches

---
 src/core/buffer/mod.rs     |  2 ++
 src/core/registry/mod.rs   | 18 +++++++++++++-
 src/core/registry/tests.rs | 50 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/src/core/buffer/mod.rs b/src/core/buffer/mod.rs
index fbfb99c..8540ee8 100644
--- a/src/core/buffer/mod.rs
+++ b/src/core/buffer/mod.rs
@@ -44,6 +44,7 @@ type NearestTransforms<'a, T> = (Option<(&'a T, &'a Isometry)>, Option<(&'a T, &
 /// than `max_age` relative to the latest inserted timestamp are removed
 /// automatically on insert. A buffer created with [`Buffer::dynamic`] never
 /// expires entries; use [`Buffer::remove_before`] for manual cleanup.
+#[derive(Clone)]
 pub(crate) struct Buffer<T = Timestamp>
 where
     T: TimePoint,
@@ -118,6 +119,7 @@ where
 /// a time series of dynamic samples. Keeping the kind structural — instead
 /// of a flag re-derived from the stored data — makes it impossible for a
 /// buffer to change kind when it is emptied and refilled.
+#[derive(Clone)]
 enum Kind<T>
 where
     T: TimePoint,
diff --git a/src/core/registry/mod.rs b/src/core/registry/mod.rs
index 65d6f5c..9802098 100644
--- a/src/core/registry/mod.rs
+++ b/src/core/registry/mod.rs
@@ -91,7 +91,7 @@ impl<'a> Mul for Hop<'a> {
 /// `Registry<T>` is `Send` and `Sync` when `T` is. An external `RwLock` permits
 /// concurrent readers; writers need exclusive access, and readers may wait for
 /// writers. Keep dependent queries under one guard.
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Registry<T = Timestamp>
 where
     T: TimePoint,
@@ -159,6 +159,22 @@ where
         Self::process_add_transform(t, &mut self.data, self.max_age)
     }
 
+    /// Inserts a batch atomically. An invalid transform leaves the registry unchanged.
+    ///
+    /// # Errors
+    /// Returns the first error from [`Registry::add_transform`].
+    pub fn add_transforms(
+        &mut self,
+        transforms: impl IntoIterator<Item = Transform<T>>,
+    ) -> Result<(), RegistryError<T>> {
+        let mut next = self.clone();
+        for transform in transforms {
+            next.add_transform(transform)?;
+        }
+        *self = next;
+        Ok(())
+    }
+
     /// Maps `source`-frame coordinates into `target` at `timestamp`.
     ///
     /// The argument order matches tf2's `lookupTransform(target, source, time)`.
diff --git a/src/core/registry/tests.rs b/src/core/registry/tests.rs
index 5a0f14a..a73a59b 100644
--- a/src/core/registry/tests.rs
+++ b/src/core/registry/tests.rs
@@ -3732,4 +3732,54 @@ mod registry_tests {
             "expected the moved frame to still be static, got {result:?}"
         );
     }
+    #[test]
+    fn a_failed_batch_does_not_leave_edges_or_evictions_behind() {
+        let mut registry = Registry::with_max_age(Duration::from_nanos(10));
+        let sample = |parent, child, ns, x| {
+            Transform::new(
+                parent,
+                child,
+                Vector3::new(x, 0.0, 0.0),
+                Quaternion::identity(),
+                Stamp::At(Timestamp::from_nanos(ns)),
+            )
+            .unwrap()
+        };
+        registry
+            .add_transform(sample("map", "base", 1, 1.0))
+            .unwrap();
+        let result = registry.add_transforms([
+            sample("map", "base", 100, 2.0),
+            sample("base", "camera", 100, 3.0),
+            sample("camera", "map", 100, 4.0),
+        ]);
+        assert!(matches!(result, Err(RegistryError::CycleDetected)));
+        assert_eq!(
+            registry
+                .get_transform("map", "base", Timestamp::from_nanos(1))
+                .unwrap()
+                .translation()
+                .x,
+            1.0
+        );
+        assert!(
+            registry
+                .get_transform("base", "camera", Timestamp::from_nanos(100))
+                .is_err()
+        );
+        registry
+            .add_transforms([
+                sample("map", "base", 2, 2.0),
+                sample("base", "camera", 2, 3.0),
+            ])
+            .unwrap();
+        assert_eq!(
+            registry
+                .get_transform("map", "camera", Timestamp::from_nanos(2))
+                .unwrap()
+                .translation()
+                .x,
+            5.0
+        );
+    }
 }