[half-edge] addEdge return two HalfEdges -- that are symmetrical

TODO.md

@@ -1,6 +1,12 @@
 # half-edge
 
-[half-edge] `addEdge` return two `HalfEdge`s -- that are symmetrical
+[half-edge] `Mod` has `nodeCounters` -- remove `globalNodeCounters`
+
+[half-edge] `Mod` has `halfEdgeCounter`
+
+[half-edge] `createHalfEdgeId`
+
+[half-edge] `addEdge` -- generate `id` and add `HalfEdge`s to `net.halfEdgeEntries`
 
 [half-edge] `PortEntry` -- `connection` through `HalfEdge`
 

src/lang/net/addEdge.ts

@@ -0,0 +1,12 @@
+import { HalfEdge } from "../half-edge"
+import { Mod } from "../mod"
+import { Net } from "../net"
+
+export function addEdge(
+  net: Net,
+  mod: Mod,
+): { first: HalfEdge; second: HalfEdge } {
+  const first = { id: "" }
+  const second = { id: "" }
+  return { first, second }
+}