From 8767c789b866a42f0fdd9abe1506e2b65d9df9b4 Mon Sep 17 00:00:00 2001
From: Hanno Braun <hanno@braun-odw.eu>
Date: Thu, 4 May 2023 11:14:42 +0200
Subject: [PATCH] Add infrastructure for tracking object insertion

---
 crates/fj-kernel/src/operations/insert.rs | 27 +++++++++++++++++++++++
 crates/fj-kernel/src/operations/mod.rs    |  2 +-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/crates/fj-kernel/src/operations/insert.rs b/crates/fj-kernel/src/operations/insert.rs
index 9fe879f46..f76b3d9d6 100644
--- a/crates/fj-kernel/src/operations/insert.rs
+++ b/crates/fj-kernel/src/operations/insert.rs
@@ -50,3 +50,30 @@ impl_insert!(
     Surface, surfaces;
     Vertex, vertices;
 );
+
+/// Indicate whether an object has been inserted
+///
+/// Intended to be used as a type parameter bound for structs that need to track
+/// whether their contents have been inserted or not.
+pub trait IsInserted {
+    /// The type of the object for which the insertion status is tracked
+    type T<T>;
+}
+
+/// Indicate that an object has been inserted
+///
+/// See [`IsInserted`].
+pub struct IsInsertedYes;
+
+impl IsInserted for IsInsertedYes {
+    type T<T> = Handle<T>;
+}
+
+/// Indicate that an object has not been inserted
+///
+/// See [`IsInserted`].
+pub struct IsInsertedNo;
+
+impl IsInserted for IsInsertedNo {
+    type T<T> = T;
+}
diff --git a/crates/fj-kernel/src/operations/mod.rs b/crates/fj-kernel/src/operations/mod.rs
index 07d818c66..de4ebc596 100644
--- a/crates/fj-kernel/src/operations/mod.rs
+++ b/crates/fj-kernel/src/operations/mod.rs
@@ -10,7 +10,7 @@ pub use self::{
         BuildCycle, BuildFace, BuildHalfEdge, BuildShell, BuildSurface,
         Polygon, Tetrahedron,
     },
-    insert::Insert,
+    insert::{Insert, IsInserted, IsInsertedNo, IsInsertedYes},
     join::JoinCycle,
     update::{UpdateCycle, UpdateFace, UpdateHalfEdge, UpdateShell},
 };