Minimal RFC4180-ish CSV parser

parseCSV.ts

import fs from 'fs';

// Minimal RFC4180-ish CSV parser: handles quoted fields with embedded commas.
export function parseCsv(filePath: string): string[][] {
  const content = fs.readFileSync(filePath, 'utf-8').replace(/\r\n/g, '\n').trim();
  const rows: string[][] = [];

  for (const line of content.split('\n')) {
    const fields: string[] = [];
    let field = '';
    let inQuotes = false;

    for (let i = 0; i < line.length; i++) {
      const char = line[i];
      if (inQuotes) {
        if (char === '"' && line[i + 1] === '"') {
          field += '"';
          i++;
        } else if (char === '"') {
          inQuotes = false;
        } else {
          field += char;
        }
      } else if (char === '"') {
        inQuotes = true;
      } else if (char === ',') {
        fields.push(field);
        field = '';
      } else {
        field += char;
      }
    }
    fields.push(field);
    rows.push(fields);
  }

  return rows;
}