feat: finish the homepage plugin, move service links and canvas out of core (B19)

plugins/homepage/tests/frontend/canvas/snapToGrid.test.ts

@@ -0,0 +1,42 @@
+import { describe, it, expect } from "vitest";
+import {
+  snapToGrid,
+  snapToGridFloor,
+} from "../../../src/frontend/canvas/snapToGrid.js";
+import { GRID_SIZE } from "../../../src/frontend/types.js";
+
+describe("snapToGrid", () => {
+  it("snaps to nearest grid multiple", () => {
+    expect(snapToGrid(0)).toBe(0);
+    expect(snapToGrid(GRID_SIZE)).toBe(GRID_SIZE);
+    expect(snapToGrid(GRID_SIZE * 2)).toBe(GRID_SIZE * 2);
+  });
+
+  it("rounds to nearest (up when exactly halfway)", () => {
+    expect(snapToGrid(GRID_SIZE / 2)).toBe(GRID_SIZE);
+    expect(snapToGrid(GRID_SIZE * 1.5)).toBe(GRID_SIZE * 2);
+  });
+
+  it("rounds down when below halfway", () => {
+    expect(snapToGrid(GRID_SIZE * 0.4)).toBe(0);
+    expect(snapToGrid(GRID_SIZE * 1.4)).toBe(GRID_SIZE);
+  });
+
+  it("works with negative values", () => {
+    expect(snapToGrid(-GRID_SIZE)).toBe(-GRID_SIZE);
+    expect(snapToGrid(-GRID_SIZE * 0.4)).toBeCloseTo(0);
+  });
+});
+
+describe("snapToGridFloor", () => {
+  it("always rounds down to floor multiple", () => {
+    expect(snapToGridFloor(GRID_SIZE - 1)).toBe(0);
+    expect(snapToGridFloor(GRID_SIZE)).toBe(GRID_SIZE);
+    expect(snapToGridFloor(GRID_SIZE + 1)).toBe(GRID_SIZE);
+    expect(snapToGridFloor(GRID_SIZE * 2 - 1)).toBe(GRID_SIZE);
+  });
+
+  it("handles zero", () => {
+    expect(snapToGridFloor(0)).toBe(0);
+  });
+});