From c30828c7d4a1299865991756c5da246ec7dca947 Mon Sep 17 00:00:00 2001
From: Hanno Braun <hello@hannobraun.com>
Date: Fri, 17 May 2024 14:13:43 +0200
Subject: [PATCH 1/3] Refactor to prepare for follow-on change

---
 .../src/queries/all_half_edges_with_surface.rs        | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/crates/fj-core/src/queries/all_half_edges_with_surface.rs b/crates/fj-core/src/queries/all_half_edges_with_surface.rs
index 55fa85d9f..96620cb3b 100644
--- a/crates/fj-core/src/queries/all_half_edges_with_surface.rs
+++ b/crates/fj-core/src/queries/all_half_edges_with_surface.rs
@@ -17,15 +17,16 @@ impl AllHalfEdgesWithSurface for Face {
         &self,
         result: &mut Vec<(Handle<HalfEdge>, Handle<Surface>)>,
     ) {
-        for cycle in self.region().all_cycles() {
-            result.extend(
+        self.region()
+            .all_cycles()
+            .map(|cycle| {
                 cycle
                     .half_edges()
                     .iter()
                     .cloned()
-                    .map(|half_edge| (half_edge, self.surface().clone())),
-            );
-        }
+                    .map(|half_edge| (half_edge, self.surface().clone()))
+            })
+            .for_each(|iter| result.extend(iter))
     }
 }
 

From eb32d919b131ad8616ed819ce0d3abdcc144892e Mon Sep 17 00:00:00 2001
From: Hanno Braun <hello@hannobraun.com>
Date: Fri, 17 May 2024 14:14:20 +0200
Subject: [PATCH 2/3] Refactor to simplify

---
 crates/fj-core/src/queries/all_half_edges_with_surface.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crates/fj-core/src/queries/all_half_edges_with_surface.rs b/crates/fj-core/src/queries/all_half_edges_with_surface.rs
index 96620cb3b..70e221a0f 100644
--- a/crates/fj-core/src/queries/all_half_edges_with_surface.rs
+++ b/crates/fj-core/src/queries/all_half_edges_with_surface.rs
@@ -19,14 +19,14 @@ impl AllHalfEdgesWithSurface for Face {
     ) {
         self.region()
             .all_cycles()
-            .map(|cycle| {
+            .flat_map(|cycle| {
                 cycle
                     .half_edges()
                     .iter()
                     .cloned()
                     .map(|half_edge| (half_edge, self.surface().clone()))
             })
-            .for_each(|iter| result.extend(iter))
+            .for_each(|r| result.push(r))
     }
 }
 

From 61011b28d2808099de27938a11070ee2bae725ee Mon Sep 17 00:00:00 2001
From: Hanno Braun <hello@hannobraun.com>
Date: Fri, 17 May 2024 14:19:04 +0200
Subject: [PATCH 3/3] Refactor query to not require allocations

---
 .../queries/all_half_edges_with_surface.rs    | 32 ++++++++-----------
 crates/fj-core/src/validate/shell.rs          |  8 ++---
 2 files changed, 17 insertions(+), 23 deletions(-)

diff --git a/crates/fj-core/src/queries/all_half_edges_with_surface.rs b/crates/fj-core/src/queries/all_half_edges_with_surface.rs
index 70e221a0f..d368bf230 100644
--- a/crates/fj-core/src/queries/all_half_edges_with_surface.rs
+++ b/crates/fj-core/src/queries/all_half_edges_with_surface.rs
@@ -8,35 +8,29 @@ pub trait AllHalfEdgesWithSurface {
     /// Access all half-edges of the object, and the surface they're on
     fn all_half_edges_with_surface(
         &self,
-        result: &mut Vec<(Handle<HalfEdge>, Handle<Surface>)>,
-    );
+    ) -> impl Iterator<Item = (Handle<HalfEdge>, Handle<Surface>)>;
 }
 
 impl AllHalfEdgesWithSurface for Face {
     fn all_half_edges_with_surface(
         &self,
-        result: &mut Vec<(Handle<HalfEdge>, Handle<Surface>)>,
-    ) {
-        self.region()
-            .all_cycles()
-            .flat_map(|cycle| {
-                cycle
-                    .half_edges()
-                    .iter()
-                    .cloned()
-                    .map(|half_edge| (half_edge, self.surface().clone()))
-            })
-            .for_each(|r| result.push(r))
+    ) -> impl Iterator<Item = (Handle<HalfEdge>, Handle<Surface>)> {
+        self.region().all_cycles().flat_map(|cycle| {
+            cycle
+                .half_edges()
+                .iter()
+                .cloned()
+                .map(|half_edge| (half_edge, self.surface().clone()))
+        })
     }
 }
 
 impl AllHalfEdgesWithSurface for Shell {
     fn all_half_edges_with_surface(
         &self,
-        result: &mut Vec<(Handle<HalfEdge>, Handle<Surface>)>,
-    ) {
-        for face in self.faces() {
-            face.all_half_edges_with_surface(result);
-        }
+    ) -> impl Iterator<Item = (Handle<HalfEdge>, Handle<Surface>)> {
+        self.faces()
+            .into_iter()
+            .flat_map(|face| face.all_half_edges_with_surface())
     }
 }
diff --git a/crates/fj-core/src/validate/shell.rs b/crates/fj-core/src/validate/shell.rs
index f06fb6054..7c7f73654 100644
--- a/crates/fj-core/src/validate/shell.rs
+++ b/crates/fj-core/src/validate/shell.rs
@@ -84,8 +84,8 @@ impl ShellValidationError {
         config: &ValidationConfig,
         errors: &mut Vec<ValidationError>,
     ) {
-        let mut edges_and_surfaces = Vec::new();
-        shell.all_half_edges_with_surface(&mut edges_and_surfaces);
+        let edges_and_surfaces =
+            shell.all_half_edges_with_surface().collect::<Vec<_>>();
 
         for (edge_a, surface_a) in &edges_and_surfaces {
             for (edge_b, surface_b) in &edges_and_surfaces {
@@ -230,8 +230,8 @@ impl ShellValidationError {
         config: &ValidationConfig,
         errors: &mut Vec<ValidationError>,
     ) {
-        let mut edges_and_surfaces = Vec::new();
-        shell.all_half_edges_with_surface(&mut edges_and_surfaces);
+        let edges_and_surfaces =
+            shell.all_half_edges_with_surface().collect::<Vec<_>>();
 
         // This is O(N^2) which isn't great, but we can't use a HashMap since we
         // need to deal with float inaccuracies. Maybe we could use some smarter