import { describe, it, expect } from "vitest";
import { compareVersions, projectPace } from "./ops";

/**
 * The countdown's whole job is to say "you are not going to make it" early
 * enough to do something about it, so the arithmetic behind that sentence is
 * worth pinning down.
 */
describe("projectPace", () => {
  it("calls it behind when the trailing rate overruns the date", () => {
    // 29 shots to go, a fortnight left, 8 delivered last week: 1.14/day
    // against the 2.07/day needed, projecting 25.4 days of work — 11.4 days
    // past the date, rounded up to a whole day late.
    const pace = projectPace(29, 14, 8);
    expect(pace.verdict).toBe("behind");
    expect(pace.requiredPerDay).toBeCloseTo(2.07, 2);
    expect(pace.actualPerDay).toBeCloseTo(1.14, 2);
    expect(pace.daysBehind).toBe(12);
  });

  it("calls a rate that only just lands tight rather than fine", () => {
    // Finishing on the last available day leaves no room for a QC failure.
    expect(projectPace(10, 10, 7).verdict).toBe("tight");
  });

  it("is on track with real slack", () => {
    const pace = projectPace(5, 30, 7);
    expect(pace.verdict).toBe("ahead");
    expect(pace.daysBehind).toBeNull();
  });

  it("separates a stall from being merely slow", () => {
    // Nothing shipped in a week is not a slow rate, it is no rate at all —
    // dividing by it would project infinity.
    const pace = projectPace(12, 20, 0);
    expect(pace.verdict).toBe("stalled");
    expect(pace.daysBehind).toBeNull();
  });

  it("reports how far past the date an unfinished episode is", () => {
    const pace = projectPace(3, -5, 4);
    expect(pace.verdict).toBe("overdue");
    expect(pace.daysBehind).toBe(5);
  });

  it("is complete once nothing is left, whatever the rate", () => {
    expect(projectPace(0, 3, 0).verdict).toBe("complete");
    expect(projectPace(0, 3, 0).requiredPerDay).toBe(0);
  });

  it("does not divide by zero on the due date itself", () => {
    // daysLeft 0 means "today": the work still has to be quoted per day.
    expect(projectPace(4, 0, 7).requiredPerDay).toBe(4);
    expect(Number.isFinite(projectPace(4, 0, 7).requiredPerDay)).toBe(true);
  });
});

/**
 * The farm strip flags machines running an older worker than the newest one
 * out there, which is only as reliable as this comparison: a plain string
 * compare ranks "1.10.0" below "1.9.0" and would quietly stop reporting drift
 * on the day the minor version reaches double digits.
 */
describe("compareVersions", () => {
  it("orders by numeric component, not lexically", () => {
    expect(compareVersions("1.10.0", "1.9.0")).toBeGreaterThan(0);
    expect(compareVersions("1.9.0", "1.10.0")).toBeLessThan(0);
  });

  it("ignores the build stamp publish.ps1 appends", () => {
    // The exe reports "1.6.1+fe420b9"; two machines on the same release built
    // from different commits are not drifting.
    expect(compareVersions("1.6.1+fe420b9", "1.6.1")).toBe(0);
    expect(compareVersions("1.6.1+fe420b9", "1.6.0+2a88880")).toBeGreaterThan(0);
  });

  it("treats a missing component as zero", () => {
    expect(compareVersions("1.6", "1.6.0")).toBe(0);
    expect(compareVersions("1.6", "1.6.1")).toBeLessThan(0);
  });

  it("is transitive enough to pick a maximum", () => {
    const versions = ["1.5.2", "1.6.1", "1.6.0", "1.10.0"];
    const latest = versions.reduce((a, b) => (compareVersions(a, b) >= 0 ? a : b));
    expect(latest).toBe("1.10.0");
  });
});