/**
 * Header reading for the device API.
 *
 * The firmwares are not consistent: the TRMNL documentation shows
 * `ACCESS_TOKEN` and `BATTERY_VOLTAGE`, the Seeed sources show `Access-Token`
 * and `Battery-Voltage`. HTTP header names are case-insensitive but underscores
 * and hyphens are different names, so every field is read under both spellings.
 * Being liberal here costs nothing; being wrong costs a blank shop window.
 */

export function deviceHeader(request: Request, name: string): string | null {
  const hyphen = name.replace(/_/g, '-');
  const underscore = name.replace(/-/g, '_');
  return request.headers.get(hyphen) ?? request.headers.get(underscore);
}

export function deviceNumber(request: Request, name: string): number | null {
  const raw = deviceHeader(request, name);
  if (raw === null || raw.trim() === '') {
    return null;
  }
  const value = Number(raw);
  return Number.isFinite(value) ? value : null;
}

/** The caller's address, as seen through whatever proxy is in front of us. */
export function clientIp(request: Request): string {
  const forwarded = request.headers.get('x-forwarded-for');
  if (forwarded) {
    return forwarded.split(',')[0]?.trim() ?? 'unknown';
  }
  return request.headers.get('x-real-ip') ?? 'unknown';
}