feat: initial Lam Agent extension (#1)

src/__tests__/location.test.ts

@@ -0,0 +1,68 @@
+import { describe, expect, it } from "vitest";
+import { describeTimezone, getLocationContext, utcOffsetLabel, weekdayName } from "../lib/location";
+
+describe("describeTimezone", () => {
+  it("splits a simple zone into region and city", () => {
+    expect(describeTimezone("Asia/Manila")).toEqual({ region: "Asia", city: "Manila" });
+  });
+
+  it("handles zones with more than two segments", () => {
+    expect(describeTimezone("America/Argentina/Salta")).toEqual({ region: "America", city: "Salta" });
+  });
+
+  it("underscores become spaces", () => {
+    expect(describeTimezone("America/New_York")).toEqual({ region: "America", city: "New York" });
+  });
+
+  it("returns nothing for a bare zone like UTC", () => {
+    expect(describeTimezone("UTC")).toEqual({});
+  });
+});
+
+describe("utcOffsetLabel", () => {
+  it("renders a GMT offset for a fixed zone", () => {
+    const date = new Date("2026-01-02T03:04:05Z");
+    expect(utcOffsetLabel(date, "Asia/Manila")).toContain("+08:00");
+  });
+
+  it("reflects daylight saving rather than a fixed offset", () => {
+    const winter = utcOffsetLabel(new Date("2026-01-15T12:00:00Z"), "America/New_York");
+    const summer = utcOffsetLabel(new Date("2026-07-15T12:00:00Z"), "America/New_York");
+
+    expect(winter).not.toBe(summer);
+    expect(winter).toContain("-05:00");
+    expect(summer).toContain("-04:00");
+  });
+});
+
+describe("weekdayName", () => {
+  it("names the weekday in the requested zone", () => {
+    // 2026-01-02T03:04:05Z is a Friday in UTC.
+    expect(weekdayName(new Date("2026-01-02T03:04:05Z"), "UTC")).toBe("Friday");
+  });
+
+  it("respects the zone when the local date differs from UTC", () => {
+    // 2026-01-02T23:30Z is still Friday in UTC but already Saturday in Manila.
+    const late = new Date("2026-01-02T23:30:00Z");
+    expect(weekdayName(late, "UTC")).toBe("Friday");
+    expect(weekdayName(late, "Asia/Manila")).toBe("Saturday");
+  });
+});
+
+describe("getLocationContext", () => {
+  it("reports the requested zone with its parts", () => {
+    const context = getLocationContext(new Date("2026-01-02T03:04:05Z"), "Asia/Manila");
+
+    expect(context.timezone).toBe("Asia/Manila");
+    expect(context.city).toBe("Manila");
+    expect(context.region).toBe("Asia");
+    expect(context.utcOffset).toContain("+08:00");
+    expect(context.locale.length).toBeGreaterThan(0);
+  });
+
+  it("still returns a usable context for an unknown zone", () => {
+    const context = getLocationContext(new Date("2026-01-02T03:04:05Z"), "Not/AReal_Zone");
+    expect(context.timezone).toBe("Not/AReal_Zone");
+    expect(context.utcOffset).toBe("UTC");
+  });
+});