import type { FastifyReply } from 'fastify';

/**
 * Parse a numeric ID from route params.
 * Returns the parsed number, or sends a 400 response and returns null.
 *
 * Usage:
 *   const id = parseIdParam(request.params.id, reply);
 *   if (id === null) return;
 */
export function parseIdParam(
  raw: string,
  reply: FastifyReply,
  label = 'ID',
): number | null {
  const id = parseInt(raw, 10);
  if (isNaN(id)) {
    reply.status(400).send({
      statusCode: 400,
      error: 'Bad Request',
      message: `${label} must be a number`,
    });
    return null;
  }
  return id;
}