feuerwerk/src/editor/sound/waveView.ts

import { clamp } from '../../ui';

/**
 * The time axis of the Sound tab (#343), apart from Pixi so a test can drive it: seconds run left to
 * right, `x` is measured from the left edge of the area that shows the wave.
 */
export interface WaveView {
  /** Pixels from the area's left edge to second 0. */
  panX: number;
  pxPerSecond: number;
}

/** From a few minutes across a screen to a sample every few pixels at 48 kHz. */
export const MIN_PX_PER_SECOND = 0.5;
export const MAX_PX_PER_SECOND = 200_000;
/** How far either end of the file can be panned in from its edge of the area, as a share of its width. */
const LEAD = 0.5;
/** Pixels either side of a handle that grab it. */
export const EDGE_REACH = 6;

export function secondsToX(view: WaveView, seconds: number): number {
  return view.panX + seconds * view.pxPerSecond;
}

export function xToSeconds(view: WaveView, x: number): number {
  return (x - view.panX) / view.pxPerSecond;
}

/** Zooms about `x`, so the second under the pointer stays under it. */
export function zoomWave(view: WaveView, factor: number, x: number): WaveView {
  const pxPerSecond = clamp(view.pxPerSecond * factor, MIN_PX_PER_SECOND, MAX_PX_PER_SECOND);
  return { panX: x - xToSeconds(view, x) * pxPerSecond, pxPerSecond };
}

/** The whole file across `width`, a little room either side. */
export function fitWave(duration: number, width: number, margin: number): WaveView {
  const room = Math.max(1, width - margin * 2);
  const pxPerSecond = clamp(room / Math.max(1e-6, duration), MIN_PX_PER_SECOND, MAX_PX_PER_SECOND);
  return { panX: margin, pxPerSecond };
}

/**
 * As the music tabs have it across and down: the start of the file no further in than half the
 * width, its end no further in from the right – and a file that fits is not pushed off the left.
 */
export function clampWave(view: WaveView, duration: number, width: number): WaveView {
  const lead = width * LEAD;
  const least = Math.min(0, width - lead - duration * view.pxPerSecond);
  return { ...view, panX: clamp(view.panX, least, lead) };
}

/** How far the wave's height zooms: out to a quarter, in to a sixteenth of full scale (#357). */
export const MIN_LEVEL = 0.25;
export const MAX_LEVEL = 16;
/** Decibels apart the level scale's marks are. */
const LEVEL_STEP_DB = 6;
/** The quietest mark the scale goes down to. */
const QUIETEST_DB = -96;

export function zoomLevel(level: number, factor: number): number {
  return clamp(level * factor, MIN_LEVEL, MAX_LEVEL);
}

/** Pixels from the middle of the wave an amplitude is drawn at, `half` being full scale at level 1. */
export function levelOffset(amplitude: number, level: number, half: number): number {
  return amplitude * level * half;
}

/**
 * Pixels from the middle the file and its clip reach up and down: full scale and `inset` around it,
 * zoomed out short of the area, zoomed in never past its `room` (#357).
 */
export function fileReach(level: number, half: number, inset: number, room: number): number {
  return Math.min(room, levelOffset(1, level, half) + inset);
}

/**
 * The marks of the level scale: every 6 dB down from 0, as far from the middle as they are drawn.
 * Only those within `room` of the middle and at least `minPx` from it – 6 dB halve the distance,
 * so that keeps them as far apart from each other too.
 */
export function levelMarks(
  level: number,
  half: number,
  room: number,
  minPx: number,
): { db: number; offset: number }[] {
  const marks: { db: number; offset: number }[] = [];
  for (let db = 0; db >= QUIETEST_DB; db -= LEVEL_STEP_DB) {
    const offset = levelOffset(10 ** (db / 20), level, half);
    if (offset < minPx) break;
    if (offset <= room) marks.push({ db, offset });
  }
  return marks;
}

/** Seconds between the ruler's labels: 1, 2 or 5 times a power of ten, at least `minPx` apart. */
export function rulerStep(pxPerSecond: number, minPx: number): number {
  const rough = minPx / pxPerSecond;
  const power = 10 ** Math.floor(Math.log10(rough));
  for (const step of [1, 2, 5, 10]) if (step * power >= rough) return step * power;
  return 10 * power;
}

/** A second as the ruler writes it, with as many decimals as its step needs. */
export function rulerLabel(seconds: number, step: number): string {
  const decimals = Math.max(0, Math.min(6, -Math.floor(Math.log10(step) + 1e-9)));
  if (seconds >= 60) {
    const minutes = Math.floor(seconds / 60);
    const rest = (seconds - minutes * 60).toFixed(decimals);
    return `${minutes}:${rest.padStart(decimals > 0 ? decimals + 3 : 2, '0')}`;
  }
  return `${seconds.toFixed(decimals)}s`;
}

/** The stretch a sound plays, in seconds of its file: `end` is never 0 here. */
export interface CutSpan {
  start: number;
  end: number;
}

/** The span an asset's start and end mean in a file of `duration`: an end of 0, or past it, is its end. */
export function spanOf(start: number, end: number, duration: number): CutSpan {
  const to = end > 0 ? Math.min(end, duration) : duration;
  const from = clamp(start, 0, Math.max(0, to));
  return { start: from, end: Math.max(from, to) };
}

/** Which handle is at `x`, the nearer one where both are in reach. */
export function edgeAt(view: WaveView, span: CutSpan, x: number): 'start' | 'end' | null {
  const toStart = Math.abs(secondsToX(view, span.start) - x);
  const toEnd = Math.abs(secondsToX(view, span.end) - x);
  if (Math.min(toStart, toEnd) > EDGE_REACH) return null;
  return toEnd < toStart || (toEnd === toStart && x > secondsToX(view, span.end)) ? 'end' : 'start';
}

/**
 * The span a drag leaves: one edge moved to `at`, or with no edge a new span from where it was
 * pressed to `at`. Held inside the file and at least `least` seconds long; an edge dragged past the
 * other stops there.
 */
export function draggedSpan(
  span: CutSpan,
  edge: 'start' | 'end' | null,
  from: number,
  at: number,
  duration: number,
  least: number,
): CutSpan {
  const inFile = (s: number) => clamp(s, 0, duration);
  const gap = Math.min(least, duration);
  if (edge === 'start') return { start: Math.min(inFile(at), span.end - gap), end: span.end };
  if (edge === 'end') return { start: span.start, end: Math.max(inFile(at), span.start + gap) };
  const [a, b] = [inFile(from), inFile(at)].sort((p, q) => p - q) as [number, number];
  return b - a >= gap ? { start: a, end: b } : { start: a, end: Math.min(duration, a + gap) };
}

/** A clip of the sound as its band in the strip (#357). */
export interface ClipBand {
  id: string;
  span: CutSpan;
}

/** The clip whose band is at `x`, the one drawn last where bands lie over each other; null for none. */
export function clipAt(view: WaveView, bands: readonly ClipBand[], x: number): string | null {
  for (let i = bands.length - 1; i >= 0; i--) {
    const { id, span } = bands[i]!;
    if (x >= secondsToX(view, span.start) && x <= secondsToX(view, span.end)) return id;
  }
  return null;
}

/** What a clip stores for a span: seconds to the nearest sample, an end at the end of the file as 0. */
export function storedCut(span: CutSpan, duration: number, rate: number): { start: number; end: number } {
  const sample = 1 / rate;
  const start = span.start < sample / 2 ? 0 : roundTo(span.start, rate);
  const end = duration - span.end < sample / 2 ? 0 : roundTo(span.end, rate);
  return { start, end };
}

/** To the nearest sample, written short. */
function roundTo(seconds: number, rate: number): number {
  return Number((Math.round(seconds * rate) / rate).toFixed(6));
}

/** Samples each block of `WavePeaks` covers. */
export const PEAK_BLOCK = 256;

/** The lowest and highest sample of each block of a sound, over all its channels. */
export interface WavePeaks {
  min: Float32Array;
  max: Float32Array;
}

export function wavePeaks(channels: readonly Float32Array[]): WavePeaks {
  const length = channels[0]?.length ?? 0;
  const blocks = Math.ceil(length / PEAK_BLOCK);
  const min = new Float32Array(blocks).fill(Infinity);
  const max = new Float32Array(blocks).fill(-Infinity);
  for (const data of channels)
    for (let i = 0; i < data.length; i++) {
      const b = (i / PEAK_BLOCK) | 0;
      const v = data[i]!;
      if (v < min[b]!) min[b] = v;
      if (v > max[b]!) max[b] = v;
    }
  return { min, max };
}

/**
 * The lowest and highest sample from `from` up to `to` (sample indices, `to` after `from`): read
 * from the blocks where the stretch spans whole ones, from the samples at its ends.
 */
export function spanPeak(
  channels: readonly Float32Array[],
  peaks: WavePeaks,
  from: number,
  to: number,
): { min: number; max: number } {
  const length = channels[0]?.length ?? 0;
  const a = Math.max(0, Math.floor(from));
  const b = Math.min(length, Math.max(a + 1, Math.ceil(to)));
  let min = Infinity;
  let max = -Infinity;
  const raw = (s: number, e: number) => {
    for (const data of channels)
      for (let i = s; i < e; i++) {
        const v = data[i]!;
        if (v < min) min = v;
        if (v > max) max = v;
      }
  };
  const firstBlock = Math.ceil(a / PEAK_BLOCK);
  const lastBlock = Math.floor(b / PEAK_BLOCK);
  if (lastBlock <= firstBlock) raw(a, b);
  else {
    raw(a, firstBlock * PEAK_BLOCK);
    for (let k = firstBlock; k < lastBlock; k++) {
      if (peaks.min[k]! < min) min = peaks.min[k]!;
      if (peaks.max[k]! > max) max = peaks.max[k]!;
    }
    raw(lastBlock * PEAK_BLOCK, b);
  }
  return min <= max ? { min, max } : { min: 0, max: 0 };
}