const KEY_PATTERN = /^[A-Za-z_][A-Za-z0-9_]*$/;

function unquote(value: string): string {
  const trimmed = value.trim();
  if (
    (trimmed.startsWith('"') && trimmed.endsWith('"')) ||
    (trimmed.startsWith("'") && trimmed.endsWith("'"))
  ) {
    const inner = trimmed.slice(1, -1);
    if (trimmed.startsWith('"')) {
      return inner.replace(/\\n/g, '\n').replace(/\\"/g, '"').replace(/\\\\/g, '\\');
    }
    return inner;
  }
  return trimmed;
}

export function parseDotenv(content: string): {
  vars: Record<string, string>;
  errors: string[];
} {
  const vars: Record<string, string> = {};
  const errors: string[] = [];
  const lines = content.split(/\r?\n/);

  lines.forEach((line, index) => {
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) return;

    const withoutExport = trimmed.startsWith('export ') ? trimmed.slice(7).trim() : trimmed;
    const eqIndex = withoutExport.indexOf('=');
    if (eqIndex === -1) {
      errors.push(`Line ${index + 1}: missing '='`);
      return;
    }

    const key = withoutExport.slice(0, eqIndex).trim();
    const rawValue = withoutExport.slice(eqIndex + 1);

    if (!KEY_PATTERN.test(key)) {
      errors.push(`Line ${index + 1}: invalid key "${key}"`);
      return;
    }

    vars[key] = unquote(rawValue);
  });

  return { vars, errors };
}