Reader composition

readerComposition.ts

interface User {
  id: number,
  name: string,
  managerId: number,
}

// ambil dependency
const userRepo = (deps: Deps) => deps.userRepo; // Reader<Deps, UserRepository>
const logger = (deps: Deps) => deps.logger; // Reader<Deps, Logger>

// buat fungsi-fungsi dasar
const getUser = (userId: number) => fmap(repo => repo.get(userId), userRepo);
const saveUser = (user: User) => fmap(repo => repo.save(user), userRepo);
const log = (obj: User) => fmap(l => l.log('Logging.. ', obj), logger);

// komposisi! reuse fungsi-fungsi dasar
const getManager = composeK(
  getUser,
  user => (deps => user.managerId), // (user: User) => Reader<Deps, number>
  getUser
)
// komposisi! reuse fungsi-fungsi dasar
const registerNewUser = composeK(
  log,
  saveUser,
)

// gunakan
getManager(1)(deps)
registerNewUser({ id: 2, name: 'Jihad', managerId: 1 })(deps)