feat(*): one task editor, vim navigation and undo

tests/place.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest";
+import { onScreen, place } from "../src/lib/place";
+import type { Box } from "../src/lib/place";
+
+const VIEW = { width: 1280, height: 800 };
+const PANEL = { width: 320, height: 200 };
+const row = (over: Partial<Box> = {}): Box => ({
+  top: 300,
+  left: 400,
+  width: 500,
+  height: 40,
+  ...over,
+});
+
+describe("onScreen", () => {
+  it("skips the copy that is hidden and has no box", () => {
+    const hidden = row({ top: 0, left: 0, width: 0, height: 0 });
+    const shown = row();
+    expect(onScreen([hidden, shown])).toBe(shown);
+  });
+
+  it("takes the first one when several are on screen", () => {
+    const first = row();
+    expect(onScreen([first, row({ top: 500 })])).toBe(first);
+  });
+
+  it("says nothing when every copy is hidden", () => {
+    expect(onScreen([row({ width: 0, height: 0 })])).toBeNull();
+    expect(onScreen([])).toBeNull();
+  });
+});
+
+describe("place", () => {
+  it("sits just under the anchor", () => {
+    expect(place(row(), PANEL, VIEW)).toEqual({ top: 346, left: 400 });
+  });
+
+  it("flips above when there is no room below", () => {
+    expect(place(row({ top: 700 }), PANEL, VIEW)).toEqual({ top: 494, left: 400 });
+  });
+
+  it("stays inside the window when there is room neither way", () => {
+    const tall = { width: 320, height: 780 };
+    const spot = place(row({ top: 400 }), tall, VIEW);
+    expect(spot.top).toBeGreaterThanOrEqual(10);
+    expect(spot.top + tall.height).toBeLessThanOrEqual(VIEW.height);
+  });
+
+  it("pulls back from the right edge", () => {
+    expect(place(row({ left: 1200 }), PANEL, VIEW).left).toBe(950);
+  });
+
+  it("never goes off the left edge", () => {
+    expect(place(row({ left: -40 }), PANEL, VIEW).left).toBe(10);
+  });
+
+  it("centres rather than hiding in the corner with nothing to anchor to", () => {
+    expect(place(null, PANEL, VIEW)).toEqual({ top: 300, left: 480 });
+  });
+});