// Minimal RFC4180 CSV parser and helpers.
const fs = require('fs');
function parseCSV(text) {
  if (text.charCodeAt(0) === 0xFEFF) text = text.slice(1);
  const rows = []; let row = [], f = '', q = false;
  for (let i = 0; i < text.length; i++) {
    const c = text[i];
    if (q) { if (c === '"') { if (text[i+1] === '"') { f += '"'; i++; } else q = false; } else f += c; }
    else if (c === '"') q = true;
    else if (c === ',') { row.push(f); f = ''; }
    else if (c === '\n') { row.push(f.replace(/\r$/, '')); rows.push(row); row = []; f = ''; }
    else f += c;
  }
  if (f !== '' || row.length) { row.push(f); rows.push(row); }
  return rows;
}
function readCSV(p) { return parseCSV(fs.readFileSync(p, 'utf8')); }
function num(s) { if (s == null) return null; s = String(s).replace(/[,\s]/g, ''); if (s === '' || s === '.') return null; const v = Number(s); return isNaN(v) ? null : v; }
function toCSV(rows) { return rows.map(r => r.map(v => { v = v == null ? '' : String(v); return /[",\n]/.test(v) ? '"' + v.replace(/"/g, '""') + '"' : v; }).join(',')).join('\n') + '\n'; }
module.exports = { parseCSV, readCSV, num, toCSV };