Fix Sweep edge duplication

Fixed cycle builder like you commented, global_edge order, and added
an edge cache.
PS: We might want to make the `SweepCache` more general

crates/fj-kernel/src/algorithms/sweep/edge.rs

@@ -37,8 +37,8 @@ impl Sweep for (&HalfEdge, &Handle<Vertex>, &Surface, Option<Color>) {
                 [
                     Some(edge.global_form().clone()),
                     Some(edge_up),
-                    Some(edge_down),
                     None,
+                    Some(edge_down),
                 ],
             )
         };

crates/fj-kernel/src/algorithms/sweep/mod.rs

@@ -11,7 +11,7 @@ use std::collections::BTreeMap;
 use fj_math::Vector;
 
 use crate::{
-    objects::{Objects, Vertex},
+    objects::{GlobalEdge, Objects, Vertex},
     services::Service,
     storage::{Handle, ObjectId},
 };
@@ -47,4 +47,6 @@ pub trait Sweep: Sized {
 pub struct SweepCache {
     /// Cache for global vertices
     pub global_vertex: BTreeMap<ObjectId, Handle<Vertex>>,
+    /// Cache for global edges
+    pub global_edge: BTreeMap<ObjectId, Handle<GlobalEdge>>,
 }

crates/fj-kernel/src/algorithms/sweep/vertex.rs

@@ -26,7 +26,11 @@ impl Sweep for Handle<Vertex> {
             .clone();
 
         let vertices = [a, b];
-        let global_edge = GlobalEdge::new().insert(objects);
+        let global_edge = cache
+            .global_edge
+            .entry(self.id())
+            .or_insert_with(|| GlobalEdge::new().insert(objects))
+            .clone();
 
         // The vertices of the returned `GlobalEdge` are in normalized order,
         // which means the order can't be relied upon by the caller. Return the

crates/fj-kernel/src/builder/cycle.rs

@@ -44,9 +44,10 @@ impl CycleBuilder {
         let half_edges = edges
             .into_iter()
             .circular_tuple_windows()
-            .map(|((prev, _, _), (_, curve, boundary))| {
+            .map(|((prev, _, _), (half_edge, curve, boundary))| {
                 HalfEdgeBuilder::new(curve, boundary)
                     .with_start_vertex(prev.start_vertex().clone())
+                    .with_global_form(half_edge.global_form().clone())
             })
             .collect();