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package com.softwaremill.sttp
import scala.concurrent.{ExecutionContext, Future, Promise}
import scala.language.higherKinds
import scala.util.Try
trait MonadError[R[_]] {
def unit[T](t: T): R[T]
def map[T, T2](fa: R[T], f: T => T2): R[T2]
def flatMap[T, T2](fa: R[T], f: T => R[T2]): R[T2]
def error[T](t: Throwable): R[T]
def flatten[T](ffa: R[R[T]]): R[T] = flatMap[R[T], T](ffa, identity)
def fromTry[T](t: Try[T]): R[T] = t.fold(error, unit)
}
trait MonadAsyncError[R[_]] extends MonadError[R] {
def async[T](register: (Either[Throwable, T] => Unit) => Unit): R[T]
}
object IdMonad extends MonadError[Id] {
override def unit[T](t: T): Id[T] = t
override def map[T, T2](fa: Id[T], f: (T) => T2): Id[T2] = f(fa)
override def flatMap[T, T2](fa: Id[T], f: (T) => Id[T2]): Id[T2] = f(fa)
override def error[T](t: Throwable): Id[T] = throw t
}
class FutureMonad(implicit ec: ExecutionContext)
extends MonadAsyncError[Future] {
override def unit[T](t: T): Future[T] = Future.successful(t)
override def map[T, T2](fa: Future[T], f: (T) => T2): Future[T2] = fa.map(f)
override def flatMap[T, T2](fa: Future[T], f: (T) => Future[T2]): Future[T2] =
fa.flatMap(f)
override def error[T](t: Throwable): Future[T] = Future.failed(t)
override def async[T](
register: ((Either[Throwable, T]) => Unit) => Unit): Future[T] = {
val p = Promise[T]()
register {
case Left(t) => p.failure(t)
case Right(t) => p.success(t)
}
p.future
}
}
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