use submodule

excalidraw/packages/math/tests/line.test.ts

@@ -0,0 +1,31 @@
+import { line, linesIntersectAt } from "../src/line";
+import { pointFrom } from "../src/point";
+
+describe("line-line intersections", () => {
+  it("should correctly detect intersection at origin", () => {
+    expect(
+      linesIntersectAt(
+        line(pointFrom(-5, -5), pointFrom(5, 5)),
+        line(pointFrom(5, -5), pointFrom(-5, 5)),
+      ),
+    ).toEqual(pointFrom(0, 0));
+  });
+
+  it("should correctly detect intersection at non-origin", () => {
+    expect(
+      linesIntersectAt(
+        line(pointFrom(0, 0), pointFrom(10, 10)),
+        line(pointFrom(10, 0), pointFrom(0, 10)),
+      ),
+    ).toEqual(pointFrom(5, 5));
+  });
+
+  it("should correctly detect parallel lines", () => {
+    expect(
+      linesIntersectAt(
+        line(pointFrom(0, 0), pointFrom(0, 10)),
+        line(pointFrom(10, 0), pointFrom(10, 10)),
+      ),
+    ).toBe(null);
+  });
+});