Created
July 8, 2019 08:08
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import arrow.core.Either | |
import arrow.core.left | |
import arrow.core.right | |
class JsonUser | |
class User | |
fun JsonUser.toUser(): User = throw RuntimeException() | |
sealed class UserQueryErrors { | |
object UserNotFound : UserQueryErrors() | |
object NetworkError : UserQueryErrors() | |
object MappingError : UserQueryErrors() | |
object DatabaseAuthError : UserQueryErrors() | |
} | |
interface NetworkDatasource { | |
fun isNetworkAvailable(): Boolean | |
fun findUserById(id: String): JsonUser? | |
} | |
interface DatabaseDatasource { | |
fun findUserById(id: String): User? | |
} | |
class DomainMapper { | |
fun jsonUserToUser(jsonUser: JsonUser): Either<UserQueryErrors, User> = | |
try { | |
jsonUser.toUser().right() | |
} catch (ex: Exception) { | |
UserQueryErrors.MappingError.left() | |
} | |
} | |
class UserRepository( | |
private val mapper: DomainMapper, | |
private val network: NetworkDatasource, | |
private val database: DatabaseDatasource | |
) { | |
private var networkPriority = true | |
fun findUser(id: String): Either<UserQueryErrors, User> = | |
if (networkPriority) { | |
if (network.isNetworkAvailable()) { | |
val jsonUser = network.findUserById(id) | |
if (jsonUser == null) UserQueryErrors.UserNotFound.left() | |
else mapper.jsonUserToUser(jsonUser) | |
} else UserQueryErrors.NetworkError.left() | |
} else { | |
try { | |
val user = database.findUserById(id) | |
user?.right() ?: UserQueryErrors.UserNotFound.left() | |
} catch (ex: Exception) { | |
UserQueryErrors.DatabaseAuthError.left() | |
} | |
} | |
} | |
class UserPresenter(private val repository: UserRepository) { | |
fun fetchUser() { | |
val either = repository.findUser("abc") | |
either.fold( | |
ifLeft = ::handleUserQueryError, | |
ifRight = ::handleUser | |
) | |
} | |
private fun handleUserQueryError(error: UserQueryErrors) = when (error) { | |
UserQueryErrors.UserNotFound -> println("User with id abc was not found") | |
UserQueryErrors.NetworkError -> println("There was an error with network") | |
UserQueryErrors.MappingError -> println("There was an error while processing") | |
UserQueryErrors.DatabaseAuthError -> println("There was an error with database") | |
} | |
private fun handleUser(user: User) { | |
println(user) | |
} | |
} |
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