Line and segment intersection

packages/math/line.test.ts

@@ -0,0 +1,51 @@
+import { line, lineIntersectsLine, lineIntersectsSegment } from "./line";
+import { point } from "./point";
+import { segment } from "./segment";
+
+describe("line-line intersections", () => {
+  it("should correctly detect intersection at origin", () => {
+    expect(
+      lineIntersectsLine(
+        line(point(-5, -5), point(5, 5)),
+        line(point(5, -5), point(-5, 5)),
+      ),
+    ).toEqual(point(0, 0));
+  });
+
+  it("should correctly detect intersection at non-origin", () => {
+    expect(
+      lineIntersectsLine(
+        line(point(0, 0), point(10, 10)),
+        line(point(10, 0), point(0, 10)),
+      ),
+    ).toEqual(point(5, 5));
+  });
+
+  it("should correctly detect parallel lines", () => {
+    expect(
+      lineIntersectsLine(
+        line(point(0, 0), point(0, 10)),
+        line(point(10, 0), point(10, 10)),
+      ),
+    ).toBe(null);
+  });
+});
+
+describe("line-segment intersections", () => {
+  it("should correctly detect intersection", () => {
+    expect(
+      lineIntersectsSegment(
+        line(point(0, 0), point(5, 0)),
+        segment(point(2, -2), point(3, 2)),
+      ),
+    ).toEqual(point(2.5, -0));
+  });
+  it("should correctly detect non-intersection", () => {
+    expect(
+      lineIntersectsSegment(
+        line(point(0, 0), point(5, 0)),
+        segment(point(3, 1), point(4, 4)),
+      ),
+    ).toEqual(null);
+  });
+});