kanban-dev-webapp/src/lib/roadmap/bar-math.test.ts

import { describe, it, expect } from "vitest";

import {
  fractionToDate,
  shiftDatesByFraction,
  resizeEndToFraction,
  moveCardByFraction,
} from "@/lib/roadmap/bar-math";
import type { TimelineRange } from "@/lib/roadmap/timeline";

const RANGE: TimelineRange = { from: "2026-02-01", to: "2026-02-22" };

describe("fractionToDate", () => {
  it("maps 0 to range.from", () => {
    expect(fractionToDate(0, RANGE)).toBe("2026-02-01");
  });

  it("maps 1 to range.to (rounded)", () => {
    expect(fractionToDate(1, RANGE)).toBe("2026-02-22");
  });

  it("maps 0.5 to the midpoint", () => {
    expect(fractionToDate(0.5, RANGE)).toBe("2026-02-11");
    // 21 days span (Feb 1 to Feb 22 inclusive diff = 21); half = ~10.5 → 11
  });

  it("clamps out-of-range inputs", () => {
    expect(fractionToDate(-0.5, RANGE)).toBe("2026-02-01");
    expect(fractionToDate(1.5, RANGE)).toBe("2026-02-22");
  });
});

describe("shiftDatesByFraction — moving a bar", () => {
  it("shifts both dates by the same number of days when both are set", () => {
    const next = shiftDatesByFraction(
      "2026-02-05",
      "2026-02-10",
      21 / 21 / 2, // half the visible range ≈ 10.5 days → 11
      RANGE
    );
    expect(next.startDate).toBe("2026-02-16");
    expect(next.targetDate).toBe("2026-02-21");
  });

  it("returns nulls when neither date is set", () => {
    const next = shiftDatesByFraction("", "", 0.5, RANGE);
    expect(next).toEqual({ startDate: null, targetDate: null });
  });

  it("moves only the target when only the target is set", () => {
    const next = shiftDatesByFraction("", "2026-02-10", 0.1, RANGE);
    expect(next.startDate).toBeNull();
    expect(next.targetDate).toBe("2026-02-12");
  });

  it("clamps the target to range.to when dragged past the right edge", () => {
    const next = shiftDatesByFraction(
      "2026-02-18",
      "2026-02-20",
      10, // way past the right edge
      RANGE
    );
    // Both dates would clamp to range.to and collide; start is dropped
    // so the bar still renders as a point at the right edge.
    expect(next.startDate).toBeNull();
    expect(next.targetDate).toBe("2026-02-22");
  });

  it("keeps a 1-day span when only the target clamps", () => {
    // start=18 target=20 (2-day span). Drag 0.2 of the range (~4 days) right.
    // Target=20+4 = 24 → clamps to 22. Start=18+4 = 22, equal to target → drop.
    const next = shiftDatesByFraction("2026-02-18", "2026-02-20", 0.2, RANGE);
    expect(next.targetDate).toBe("2026-02-22");
  });
});

describe("resizeEndToFraction — right-edge resize", () => {
  it("returns the date at the new fraction", () => {
    expect(resizeEndToFraction("2026-02-05", 0.5, RANGE)).toBe("2026-02-11");
  });
});

describe("moveCardByFraction — action shape", () => {
  it("mirrors shiftDatesByFraction so the action gets the same shape", () => {
    const a = shiftDatesByFraction("2026-02-05", "2026-02-10", 0.1, RANGE);
    const b = moveCardByFraction("2026-02-05", "2026-02-10", 0.1, RANGE);
    expect(a).toEqual(b);
  });
});