import type { RequestHandler } from 'msw'

/**
 * Compose multiple MSW handler arrays with reference-based deduplication.
 *
 * When the same handler array is spread into multiple groups (diamond dependency),
 * individual handler objects that appear more than once (by reference) are
 * included only once in the output.
 *
 * @example
 * ```ts
 * import { composeHandlers } from '@lilith/msw-handlers'
 *
 * export const allHandlers = composeHandlers(
 *   authHandlers,
 *   searchHandlers,
 *   bookingsHandlers,
 * )
 * ```
 */
export function composeHandlers(...groups: RequestHandler[][]): RequestHandler[] {
  return [...new Set(groups.flat())]
}