siftlode/frontend/src/lib/chipOverflow.test.ts

import { describe, it, expect } from "vitest";
import { decideChipLayout, fitChipsWithPill, type ChipFitInput } from "./chipOverflow";

// Build measurer-style right edges for `n` chips of a fixed width, starting after a label, with a gap.
function rights(labelRight: number, widths: number[], gap: number): number[] {
  const out: number[] = [];
  let cursor = labelRight;
  for (const w of widths) {
    cursor += gap + w;
    out.push(cursor);
  }
  return out;
}

const base = (over: Partial<ChipFitInput> = {}): ChipFitInput => {
  const gap = 6;
  const labelRight = 60;
  const widths = [50, 50, 50]; // 3 chips
  return {
    n: 3,
    labelRight,
    chipRights: rights(labelRight, widths, gap),
    plusW: 40,
    clearW: 6 + 60,
    avail: 1000,
    gap,
    narrowPx: 420,
    ...over,
  };
};

describe("decideChipLayout", () => {
  it("shows all chips when the whole set plus Clear all fits", () => {
    expect(decideChipLayout(base({ avail: 1000 }))).toEqual({ mode: "all", visible: 3 });
  });

  it("empty chip set is a no-op 'all' with 0 visible", () => {
    expect(decideChipLayout(base({ n: 0, chipRights: [] }))).toEqual({ mode: "all", visible: 0 });
  });

  it("collapses to a single count pill on a narrow lane when overflowing", () => {
    // last chip right edge is ~228; avail below NARROW and below that -> count.
    expect(decideChipLayout(base({ avail: 200, narrowPx: 420 }))).toEqual({
      mode: "count",
      visible: 0,
    });
  });

  it("fits as many chips as leave room for the +N pill on a wide-but-tight lane", () => {
    // chip right edges: 116, 172, 228; clearW 66. all-fit needs 228+66=294 <= avail; keep avail below
    // that (so not 'all') but >= narrowPx (so not 'count'). Loop reserves gap(6)+plus(40)=46 per chip:
    // chip2 228+46=274 > 250 -> dropped; chip1 218 <= 250 -> visible 2.
    expect(decideChipLayout(base({ avail: 250, narrowPx: 200 }))).toEqual({
      mode: "some",
      visible: 2,
    });
  });

  it("reserves the +N pill width so a later chip is dropped when it wouldn't fit beside it", () => {
    // Two chips of width 100 after a label, gap 6, plus pill 40. Right edges: 166, 272. avail 300,
    // narrowPx 100 (so 300 >= narrow -> 'some'): chip0 166+46=212 <= 300 ok; chip1 272+46=318 > 300
    // -> dropped. visible 1.
    const input = base({
      n: 2,
      chipRights: rights(60, [100, 100], 6),
      plusW: 40,
      clearW: 6 + 60,
      avail: 300,
      gap: 6,
      narrowPx: 100,
    });
    expect(decideChipLayout(input)).toEqual({ mode: "some", visible: 1 });
  });

  it("falls back to the count pill when not even one chip fits beside the +N pill", () => {
    // Wide-ish lane (>= narrow) but a single very wide chip: label 60, chip width 500 -> right 566.
    // avail 430 >= narrow(420); all-fit 566+clearW > 430; loop: 566+6+40 > 430 -> k=0; labelRight
    // 60+6+40=106 <= 430 so NOT count by that guard... use narrow-avail instead: keep avail 430 but
    // make label+gap+plus exceed it to force count.
    const input = base({
      n: 1,
      labelRight: 400,
      chipRights: [966],
      plusW: 40,
      clearW: 0,
      avail: 430,
      gap: 6,
      narrowPx: 420,
    });
    // label 400 + gap 6 + plus 40 = 446 > 430 and k===0 -> count.
    expect(decideChipLayout(input)).toEqual({ mode: "count", visible: 0 });
  });
});

describe("fitChipsWithPill", () => {
  // Three chips of width 50, gap 6, starting at 0 -> right edges 50, 106, 162.
  const chipRights = rights(0, [50, 50, 50], 6);

  it("shows all chips (no pill) when the last chip's right edge fits — the whole-set fast path", () => {
    expect(fitChipsWithPill({ chipRights, pillW: 40, gap: 6, avail: 200 })).toBe(3);
  });

  it("returns 0 for an empty chip set", () => {
    expect(fitChipsWithPill({ chipRights: [], pillW: 40, gap: 6, avail: 200 })).toBe(0);
  });

  it("reserves the pill width for all but the last chip when overflowing", () => {
    // avail 120: whole set (162) doesn't fit. chip0 right 50 <= 120-(40+6)=74 ok; chip1 right 106 > 74
    // -> dropped at i=1 -> visible 1.
    expect(fitChipsWithPill({ chipRights, pillW: 40, gap: 6, avail: 120 })).toBe(1);
  });

  it("keeps the whole set via the fast path even when a reserve-for-all loop would drop chips", () => {
    // Right edges 56, 112, 118; avail 120: the whole set fits (118 <= 120). A naive loop that reserves
    // pill+gap (46) for every non-last chip would drop at chip1 (112 > 120-46=74) and show "+2" beside
    // empty space — the fast path returns all 3 instead.
    expect(fitChipsWithPill({ chipRights: [56, 112, 118], pillW: 40, gap: 6, avail: 120 })).toBe(3);
  });
});