bookhoard/web/src/audio-scrubber.test.ts

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

import {
  applyDrag,
  bufferedAheadEnd,
  bufferedSpanPct,
  chapterIndexFor,
  denseTicks,
  dragScale,
  DRAG_REF_PX,
  DRAG_SCALE_MIN,
  nearestChapterLine,
  railLiftPx,
  railSecondsAtPointer,
  railTicks,
  railWindow,
  RAIL_SPAN,
  secondsAtPointer,
  snapToChapterPx,
  TOUCH_RAIL_LIFT_MAX_PX,
  TOUCH_RAIL_MIN_DY_PX,
  touchRailSpan,
} from "./audio-scrubber";

// An 86-hour book (KJV-shaped: 1189 even chapters) and a 26-hour
// single-file book (Gardens-shaped: 34 chapters).
const duration86h = 310_320;
const chapters1189 = Array.from({ length: 1189 }, (_, i) => ({ start: (i * duration86h) / 1189 }));
const duration26h = 93_807;
const chapters34 = Array.from({ length: 34 }, (_, i) => ({
  start: (i * duration26h) / 34,
  title: `Chapter ${i + 1}`,
}));

const rect = (width: number): DOMRect =>
  ({
    left: 100,
    right: 100 + width,
    width,
    top: 0,
    bottom: 10,
    height: 10,
    x: 100,
    y: 0,
    toJSON: () => ({}),
  }) as DOMRect;

describe("secondsAtPointer", () => {
  it("maps the bar linearly and clamps outside it", () => {
    const r = rect(800);
    expect(secondsAtPointer(100, r, duration86h)).toBe(0);
    expect(secondsAtPointer(500, r, duration86h)).toBeCloseTo(duration86h / 2, 5);
    expect(secondsAtPointer(900, r, duration86h)).toBe(duration86h);
    expect(secondsAtPointer(50, r, duration86h)).toBe(0);
    expect(secondsAtPointer(1200, r, duration86h)).toBe(duration86h);
  });

  it("is safe with degenerate rects and durations", () => {
    expect(secondsAtPointer(150, rect(0), duration86h)).toBe(0);
    expect(secondsAtPointer(150, rect(800), 0)).toBe(0);
  });
});

describe("chapterIndexFor", () => {
  it("finds the containing chapter in both shapes", () => {
    expect(chapterIndexFor(chapters1189, 0)).toBe(0);
    expect(chapterIndexFor(chapters1189, chapters1189[500].start + 1)).toBe(500);
    expect(chapterIndexFor(chapters34, chapters34[33].start + 60)).toBe(33);
    expect(chapterIndexFor(chapters34, duration26h + 5000)).toBe(33);
  });

  it("returns -1 before the first chapter and for none at all", () => {
    expect(chapterIndexFor(chapters1189, -1)).toBe(-1);
    expect(chapterIndexFor([], 100)).toBe(-1);
  });
});

describe("nearestChapterLine / snapToChapterPx (§9 pixel magnetism)", () => {
  // 34-chapter book on an 800px bar: ~23.5px between lines — the
  // radius discriminates. (On the KJV-shaped bar the 1189 lines sit
  // ~0.4px apart — magnetism lands on SOME line from anywhere, which
  // is correct for a book that dense.)
  const pxSec = 800 / duration26h; // bar px per second

  it("reports the closest line and its distance in bar pixels", () => {
    const start = chapters34[5].start;
    const near = nearestChapterLine(start + 5 / pxSec, chapters34, duration26h, 800);
    expect(near!.index).toBe(5);
    expect(near!.seconds).toBe(start);
    expect(near!.distancePx).toBeCloseTo(5, 5);
    expect(nearestChapterLine(42, [], duration26h, 800)).toBeNull();
  });

  it("finds sub-pixel lines on a book as dense as the KJV", () => {
    // 1px ≈ 633s — a seconds threshold could never fire here; a pixel
    // radius always can. This is the §9 root-cause fix.
    const dense = nearestChapterLine(duration86h / 2, chapters1189, duration86h, 489);
    expect(dense).not.toBeNull();
    expect(dense!.distancePx).toBeLessThan(0.25);
  });

  it("snaps within the pixel radius and not beyond it", () => {
    const start = chapters34[5].start;
    expect(snapToChapterPx(start + 9 / pxSec, chapters34, duration26h, 800)).toEqual({
      seconds: start,
      snapped: true,
    });
    expect(snapToChapterPx(start + 11 / pxSec, chapters34, duration26h, 800).snapped).toBe(false);
    expect(snapToChapterPx(start - 10 / pxSec, chapters34, duration26h, 800)).toEqual({
      seconds: start,
      snapped: true,
    });
  });

  it("force snaps to the nearest line regardless of radius (Shift+click)", () => {
    const a = chapters34[5].start;
    const b = chapters34[6].start;
    const mid = (a + b) / 2;
    // Radius 0 + force must land where a wide radius lands: distance
    // is ignored, nearest wins (mid+1 → the later line).
    expect(snapToChapterPx(mid + 1, chapters34, duration26h, 800, 0, true)).toEqual({
      seconds: b,
      snapped: true,
    });
    // Past the book's last line, the nearest line is still reachable.
    const last = chapters34[33].start;
    expect(snapToChapterPx(last + 1000 / pxSec, chapters34, duration26h, 800, 0, true)).toEqual({
      seconds: last,
      snapped: true,
    });
  });

  it("picks the NEAREST line when two are in radius", () => {
    const a = chapters34[5].start;
    const b = chapters34[6].start;
    const mid = (a + b) / 2;
    // Both lines sit ~11.8px from the midpoint; inside a 13px radius
    // the closer (later) one must win.
    const result = snapToChapterPx(mid + 1, chapters34, duration26h, 800, 13);
    expect(result.snapped).toBe(true);
    expect(result.seconds).toBe(b);
  });

  it("leaves the position alone with no chapters or a dead bar", () => {
    expect(snapToChapterPx(42, [], duration26h, 800)).toEqual({ seconds: 42, snapped: false });
    expect(snapToChapterPx(42, chapters34, duration26h, 0).snapped).toBe(false);
  });
});

describe("dragScale / applyDrag (§9 touch progressive precision)", () => {
  it("is 1:1 at the bar and decays an order per reference distance", () => {
    expect(dragScale(0)).toBe(1);
    expect(dragScale(DRAG_REF_PX)).toBeCloseTo(0.1, 5);
    expect(dragScale(2 * DRAG_REF_PX)).toBeCloseTo(0.01, 5);
  });

  it("is symmetric in pull direction and monotonic in |dy|", () => {
    expect(dragScale(-60)).toBe(dragScale(60));
    expect(dragScale(30)).toBeGreaterThan(dragScale(60));
    expect(dragScale(60)).toBeGreaterThan(dragScale(120));
    expect(dragScale(10_000)).toBe(DRAG_SCALE_MIN);
  });

  it("degenerates to plain travel with a dead reference", () => {
    expect(dragScale(500, 0)).toBe(1);
  });

  it("advances the cursor 1:1 at dy=0 (px → seconds at bar scale)", () => {
    // 800px bar over 26h: 100px ≈ 11726s.
    expect(applyDrag(0, 100, 0, 800 / duration26h, duration26h)).toBeCloseTo(
      (100 / 800) * duration26h,
      5,
    );
  });

  it("shrinks travel by the current zoom (incremental, not absolute)", () => {
    const pxPerSecond = 800 / duration26h;
    const onePxSeconds = 1 / pxPerSecond;
    // One reference-distance of pull = one order of magnitude finer.
    expect(applyDrag(0, 100, DRAG_REF_PX, pxPerSecond, duration26h)).toBeCloseTo(
      100 * onePxSeconds * 0.1,
      5,
    );
    // Scale changes only affect SUBSEQUENT travel: the cursor never
    // teleports when the finger pulls away mid-drag.
    expect(applyDrag(5000, 0, 3 * DRAG_REF_PX, pxPerSecond, duration26h)).toBe(5000);
  });

  it("clamps to the book in both directions", () => {
    const pxPerSecond = 800 / duration26h;
    expect(applyDrag(duration26h, 100, 0, pxPerSecond, duration26h)).toBe(duration26h);
    expect(applyDrag(1, -100, 0, pxPerSecond, duration26h)).toBe(0);
    expect(applyDrag(50, 100, 0, 0, duration26h)).toBe(50);
  });
});

describe("touch rail feedback (span shrink + lift)", () => {
  it("starts at the full ±5-min span and shrinks with the zoom", () => {
    expect(touchRailSpan(0)).toBe(RAIL_SPAN);
    expect(touchRailSpan(DRAG_REF_PX)).toBeCloseTo(RAIL_SPAN * 0.1, 5);
    expect(touchRailSpan(5 * DRAG_REF_PX)).toBe(2); // zoomed past the floor
    expect(touchRailSpan(60)).toBeLessThan(RAIL_SPAN);
  });

  it("shows the rail only past the pull threshold", () => {
    expect(TOUCH_RAIL_MIN_DY_PX).toBeGreaterThan(0);
  });

  it("lifts toward the finger, capped", () => {
    expect(railLiftPx(20)).toBe(-20); // finger above the bar → rail rises
    expect(railLiftPx(-30)).toBe(30); // finger below → rail follows down
    expect(railLiftPx(500)).toBe(-TOUCH_RAIL_LIFT_MAX_PX);
    expect(railLiftPx(-500)).toBe(TOUCH_RAIL_LIFT_MAX_PX);
  });
});

describe("denseTicks", () => {
  it("decimates an 1189-chapter book to a readable number of marks", () => {
    const ticks = denseTicks(chapters1189, duration86h, 800, 4);
    expect(ticks.length).toBeGreaterThan(50);
    expect(ticks.length).toBeLessThan(300);
    expect(ticks[0]).toBe(0);
    // kept marks are strictly increasing and spaced by the gap rule
    for (let i = 1; i < ticks.length; i += 1) {
      const gapPx =
        ((chapters1189[ticks[i]].start - chapters1189[ticks[i - 1]].start) / duration86h) * 800;
      expect(gapPx).toBeGreaterThanOrEqual(4);
    }
  });

  it("keeps every chapter for a sparse 34-chapter book", () => {
    const ticks = denseTicks(chapters34, duration26h, 800, 4);
    expect(ticks).toHaveLength(34);
  });

  it("handles degenerate inputs", () => {
    expect(denseTicks([], duration86h, 800)).toEqual([]);
    expect(denseTicks(chapters34, 0, 800)).toEqual([]);
    expect(denseTicks(chapters34, duration26h, 0)).toEqual([]);
  });
});

describe("bufferedAheadEnd", () => {
  it("returns the end of the range containing the playhead", () => {
    const ranges = [
      { start: 0, end: 2 },
      { start: 92_719, end: 93_808 },
    ];
    // A huge m4b's moov index at the tail is its own range — it must
    // NOT read as "the whole book is buffered".
    expect(bufferedAheadEnd(ranges, 0)).toBe(2);
    expect(bufferedAheadEnd(ranges, 1.5)).toBe(2);
    expect(bufferedAheadEnd(ranges, 92_800)).toBe(93_808);
  });

  it("walks into the next range when the playhead sits at a boundary", () => {
    expect(
      bufferedAheadEnd(
        [
          { start: 0, end: 10 },
          { start: 10, end: 30 },
        ],
        10,
      ),
    ).toBe(30);
  });

  it("returns null when the playhead is in a gap or ranges are empty", () => {
    expect(bufferedAheadEnd([{ start: 50, end: 60 }], 10)).toBeNull();
    expect(bufferedAheadEnd([], 10)).toBeNull();
  });
});

describe("bufferedSpanPct", () => {
  it("maps only the active track's segment on a multi-track book", () => {
    // Track 8 of the KJV shape spans ~2088s..2344s of 310320s.
    const track = { start: 2088, end: 2344 };
    const span = bufferedSpanPct(track, 2344, duration86h);
    expect(span).not.toBeNull();
    expect(span!.left).toBeCloseTo((2088 / duration86h) * 100, 5);
    expect(span!.width).toBeCloseTo(((2344 - 2088) / duration86h) * 100, 5);
    // Element buffer beyond the track end is clamped to the track.
    const clamped = bufferedSpanPct(track, 99999, duration86h);
    expect(clamped!.width).toBeCloseTo(((2344 - 2088) / duration86h) * 100, 5);
  });

  it("spans the whole bar for a single-file book (start 0, end unknown)", () => {
    const span = bufferedSpanPct({ start: 0, end: 0 }, 40_000, duration26h);
    expect(span!.left).toBe(0);
    expect(span!.width).toBeCloseTo((40_000 / duration26h) * 100, 5);
  });

  it("returns null with no track or no buffer", () => {
    expect(bufferedSpanPct(undefined, 100, duration86h)).toBeNull();
    expect(bufferedSpanPct({ start: 0, end: 0 }, null, duration86h)).toBeNull();
    expect(bufferedSpanPct({ start: 0, end: 0 }, 0, duration86h)).toBeNull();
  });
});

describe("railWindow / railSecondsAtPointer / railTicks", () => {
  it("centers a ±5min window and clamps at the book edges", () => {
    const mid = railWindow(duration26h / 2, duration26h);
    expect(mid.from).toBeCloseTo(duration26h / 2 - RAIL_SPAN / 2, 5);
    expect(mid.to).toBeCloseTo(duration26h / 2 + RAIL_SPAN / 2, 5);
    const atStart = railWindow(0, duration26h);
    expect(atStart.from).toBe(0);
    expect(atStart.to).toBe(RAIL_SPAN);
    const atEnd = railWindow(duration26h, duration26h);
    expect(atEnd.to).toBe(duration26h);
    expect(atEnd.to - atEnd.from).toBe(RAIL_SPAN);
    // A book shorter than the window clamps to the whole book.
    expect(railWindow(60, 120)).toEqual({ from: 0, to: 120 });
  });

  it("maps pointer X at minutes-per-pixel inside the window", () => {
    const r = rect(600);
    const window = { from: 3000, to: 3600 };
    expect(railSecondsAtPointer(100, r, window)).toBe(3000);
    expect(railSecondsAtPointer(400, r, window)).toBe(3300);
    expect(railSecondsAtPointer(700, r, window)).toBe(3600);
  });

  it("lists the chapter starts inside the window with titles", () => {
    // from is 1s past chapter 4's start, so chapter 4 is outside.
    const ticks = railTicks(
      { from: chapters34[3].start + 1, to: chapters34[6].start + 1 },
      chapters34,
    );
    expect(ticks.map((t) => t.title)).toEqual(["Chapter 5", "Chapter 6", "Chapter 7"]);
  });
});