/**
 * [Gitea #340] Helpers for the "Share location" confirm step: the geo URI to
 * send (RFC 5870, with the fix's accuracy as `u=` so receivers can draw a
 * radius) and a human accuracy label, so a ±3 km Wi-Fi/IP fix isn't presented
 * — or sent — as if it were exact.
 */

/** Decimals kept for an "approximate" share: 2 → ~1.1 km of latitude. */
export const APPROXIMATE_DECIMALS = 2;
/** Uncertainty reported for an approximate share (half a 0.01° cell, rounded up). */
export const APPROXIMATE_UNCERTAINTY_M = 1000;

const validAccuracy = (accuracy?: number): number | undefined =>
  typeof accuracy === 'number' && Number.isFinite(accuracy) && accuracy > 0
    ? Math.round(accuracy)
    : undefined;

export const buildGeoUri = (
  latitude: number,
  longitude: number,
  accuracy?: number,
  approximate = false,
): string => {
  const decimals = approximate ? APPROXIMATE_DECIMALS : 6;
  const u = approximate
    ? Math.max(APPROXIMATE_UNCERTAINTY_M, validAccuracy(accuracy) ?? 0)
    : validAccuracy(accuracy);
  const base = `geo:${latitude.toFixed(decimals)},${longitude.toFixed(decimals)}`;
  return u ? `${base};u=${u}` : base;
};

/** "±12 m", "±3.5 km", or undefined when the browser gave no accuracy. */
export const formatAccuracy = (accuracy?: number): string | undefined => {
  const m = validAccuracy(accuracy);
  if (m === undefined) return undefined;
  if (m < 1000) return `±${m} m`;
  const km = m / 1000;
  return `±${km < 10 ? km.toFixed(1) : Math.round(km)} km`;
};