/**
 * Everything in SI: metres, seconds, hertz, metres per second.
 *
 * The domain is deliberately small. A three-dimensional grid costs the cube of
 * its resolution, so where the flat sibling can afford 512 points across ten
 * metres this one gets 128 across two, and the number that decides whether
 * what is on screen is physics or grid dispersion is the same either way: how
 * many cells fit in a wavelength. At 128 points across 2 m a 1.5 kHz tone is
 * about fifteen cells per wavelength, which is comfortable; raise the
 * frequency and the app says when it stops being so.
 */

/** Speed of sound in air at about 20 °C, m/s. */
export const C_AIR = 343;

/** Side of the cubic domain, metres. Room-corner sized rather than
 *  hall sized, for the reason above. */
export const DOMAIN = 2;

/** Fraction of the domain given to the absorbing layer at each face. */
export const SPONGE_FRAC = 0.15;

/** Absorption rate the sponge reaches at the wall, inverse seconds. */
export const SPONGE_MAX = 9000;

/** Cells per wavelength below which what is on screen is as much grid
 *  dispersion as it is sound. */
export const POOR_RESOLUTION = 8;

/** A length in metres, written the way a person would say it. */
export const fmtLength = (m: number): string =>
  Math.abs(m) < 1 ? `${(1000 * m).toPrecision(3)} mm` : `${m.toPrecision(3)} m`;

/** A duration in seconds, likewise. */
export const fmtTime = (s: number): string => {
  const a = Math.abs(s);
  if (a > 0 && a < 1e-3) return `${(1e6 * s).toPrecision(3)} µs`;
  if (a < 1) return `${(1e3 * s).toPrecision(3)} ms`;
  return `${s.toPrecision(3)} s`;
};