PolymorphicDataSources.kt

PolymorphicDataSources.kt

class LocalDataSource<F>(A: ApplicativeError<F, Throwable>) : 
    DataSource<F>, ApplicativeError<F, Throwable> by A {
      
    private val localCache: Map<User, List<Task>> =
      mapOf(User(UserId("user1")) to listOf(Task("LocalTask assigned to user1")))

    override fun allTasksByUser(user: User): Kind<F, List<Task>> =
      Option.fromNullable(localCache[user]).fold(
        { raiseError(UserNotInLocalStorage(user)) },
        { just(it) }
      )
}

class RemoteDataSource<F>(A: Async<F>) : 
    DataSource<F>, Async<F> by A {
      
    private val internetStorage: Map<User, List<Task>> =
      mapOf(User(UserId("user2")) to listOf(Task("Remote Task assigned to user2")))

    override fun allTasksByUser(user: User): Kind<F, List<Task>> =
      async { cb ->
        Option.fromNullable(internetStorage[user]).fold(
          { cb(UserNotInRemoteStorage(user).left()) },
          { cb(it.right()) }
        )
      }
}