Sheet scale read from the sheet's text

/** "1/4" → 0.25, "1-1/2" / "1 1/2" → 1.5, "0.25" → 0.25 */
function inches(s) {
  const m = /^(\d+)\s*[- ]\s*(\d+)\s*\/\s*(\d+)$/.exec(s.trim());
  if (m) return +m[1] + +m[2] / +m[3];
  const f = /^(\d+)\s*\/\s*(\d+)$/.exec(s.trim());
  if (f) return +f[2] ? +f[1] / +f[2] : NaN;
  return Number(s.trim());
}

export function scalesInText(text) {
  const s = String(text || '');
  const out = [];
  const before = (i) => /\bscale\b\s*[:=]?\s*$/i.test(s.slice(Math.max(0, i - 16), i));
  for (const m of s.matchAll(IMPERIAL)) {
    const paper = inches(m[1]), real = +m[2] * 12 + (m[3] ? +m[3] : 0);
    if (!(paper > 0) || !(real > 0)) continue;
    const ratio = Math.round(real / paper * 1000) / 1000;
    const p = byRatio.get('i' + ratio);
    if (!p || p.group === 'Metric') continue;
    // 1" = 1'-0" is architectural (12); 1" = 10' and up engineering — both are imperial presets by ratio
    out.push({ preset: p.key, label: p.label, index: m.index, scaleWord: before(m.index) });
  }
  for (const m of s.matchAll(METRIC)) {
    const p = byRatio.get('m' + +m[1]);
    if (!p) continue;
    out.push({ preset: p.key, label: p.label, index: m.index, scaleWord: before(m.index) });
  }
  return out.sort((a, b) => a.index - b.index);
}

export function sheetScale(text) {
  const found = scalesInText(text);
  const nts = NTS.test(String(text || ''));
  if (!found.length) return { preset: null, n: 0, others: [], nts, why: nts ? 'nts' : 'none' };
  const score = new Map();
  for (const f of found) score.set(f.preset, (score.get(f.preset) || 0) + (f.scaleWord ? 2 : 1));
  const ranked = [...score.entries()].sort((a, b) => b[1] - a[1] || found.findIndex((f) => f.preset === a[0]) - found.findIndex((f) => f.preset === b[0]));
  const [preset] = ranked[0];
  return { preset, label: PRESETS.get(preset).label, n: found.filter((f) => f.preset === preset).length, others: ranked.slice(1).map(([k]) => k), nts, why: ranked.length > 1 ? 'several' : 'one' };
}