import { expect, test } from "bun:test";
import { projectStat } from "./view";
import { findStat } from "./stats";
import { fitTrend } from "./trend";

test("1Y ago matches calendar periods even when an intermediate month is missing", () => {
  const points = Array.from({ length: 25 }, (_, index) => ({
    date: new Date(Date.UTC(2024, 6 + index, 1)).toISOString().slice(0, 10),
    value: index,
  })).filter((point) => point.date !== "2025-10-01");
  const view = projectStat({ stat: findStat("cpi-yoy"), points, trend: fitTrend(points) }, "5Y");
  expect(view.latest.date).toBe("2026-07-01");
  expect(view.yearAgo).toEqual({ date: "2025-07-01", value: 12 });
  const missingBase = points.filter((point) => point.date !== "2025-07-01");
  expect(projectStat({ stat: findStat("cpi-yoy"), points: missingBase, trend: fitTrend(missingBase) }, "5Y").yearAgo).toBeNull();
});


test("daily 1Y ago clamps February 29 to February 28 instead of looking forward into March", () => {
  const points = [
    { date: "2023-02-27", value: 4.1 }, { date: "2023-02-28", value: 4.2 },
    { date: "2023-03-01", value: 4.3 }, { date: "2024-02-28", value: 4.4 },
    { date: "2024-02-29", value: 4.5 },
  ];
  const view = projectStat({ stat: findStat("ten-year"), points, trend: fitTrend(points) }, "5Y");
  expect(view.yearAgo).toEqual({ date: "2023-02-28", value: 4.2 });
});

test("an on-schedule print is not stale until its release is overdue", () => {
  const stale = (id: string, latest: string, now: string, months = 1) => {
    const points = Array.from({ length: 8 }, (_, index) => {
      const date = new Date(`${latest}T00:00:00Z`);
      date.setUTCMonth(date.getUTCMonth() - (7 - index) * months);
      return { date: date.toISOString().slice(0, 10), value: index };
    });
    return projectStat({ stat: findStat(id), points, trend: fitTrend(points) }, "5Y", { nowMs: Date.parse(`${now}T12:00:00Z`) }).observationStale;
  };
  expect(stale("pce-yoy", "2026-07-01", "2026-09-24")).toBe(false);
  expect(stale("pce-yoy", "2026-07-01", "2026-10-20")).toBe(true);
  expect(stale("cpi-yoy", "2026-08-01", "2026-10-15")).toBe(false);
  expect(stale("real-gdp", "2026-04-01", "2026-10-29", 3)).toBe(false);
  expect(stale("real-gdp", "2026-04-01", "2026-11-30", 3)).toBe(true);
});