import { afterAll, beforeAll, describe, expect, it } from "vitest";
import {
  daysFromToday,
  dueLabel,
  dueTone,
  localKey,
  monthGrid,
  nextFriday,
} from "../src/lib/due";

describe("due helpers read the day they are given", () => {
  it("labels against the given today, not the wall clock", () => {
    expect(dueLabel("2026-08-23", "2026-08-23")).toBe("today");
    expect(dueLabel("2026-08-24", "2026-08-23")).toBe("tomorrow");
    expect(dueLabel("2026-08-22", "2026-08-23")).toBe("yesterday");
    expect(dueLabel("2026-08-23", "2026-08-30")).toBe("Aug 23");
  });

  it("tones against the given today", () => {
    expect(dueTone("2026-08-22", "2026-08-23")).toBe("overdue");
    expect(dueTone("2026-08-24", "2026-08-23")).toBe("soon");
    expect(dueTone("2026-09-24", "2026-08-23")).toBe("normal");
    expect(daysFromToday("2026-09-02", "2026-08-23")).toBe(10);
  });

  it("finds the friday after the given day, never the same one", () => {
    expect(nextFriday("2026-08-23")).toBe("2026-08-28");
    expect(nextFriday("2026-08-28")).toBe("2026-09-04");
  });
});

describe("monthGrid steps by calendar day", () => {
  const zone = process.env.TZ;
  beforeAll(() => {
    process.env.TZ = "Europe/Berlin";
  });
  afterAll(() => {
    process.env.TZ = zone;
  });

  it("keeps every day once across the autumn clock change", () => {
    const keys = monthGrid(new Date(2026, 9, 1)).map(localKey);
    expect(keys).toHaveLength(42);
    expect(new Set(keys).size).toBe(42);
    expect(keys[0]).toBe("2026-09-28");
    expect(keys[27]).toBe("2026-10-25");
    expect(keys[28]).toBe("2026-10-26");
    expect(keys[41]).toBe("2026-11-08");
  });

  it("keeps every day once across the spring clock change", () => {
    const keys = monthGrid(new Date(2027, 2, 1)).map(localKey);
    expect(new Set(keys).size).toBe(42);
    expect(keys).toContain("2027-03-28");
    expect(keys).toContain("2027-03-29");
  });
});