Monads.hs

-- | Functions and type class implementations for working with Hydra's built-in Flow monad

module Hydra.Tools.Monads where

import Hydra.Compute
import Hydra.Monads hiding (fail, pure)
import qualified Hydra.Lib.Flows as Flows

import qualified Control.Monad as CM
import qualified System.IO as IO


fromEither :: Show e => (e -> String) -> Either e a -> Flow c a
fromEither printErr x = case x of
  Left e -> Flows.fail $ printErr e
  Right a -> return a

flowToIo :: s -> Flow s a -> IO.IO a
flowToIo cx f = case mv of
    Just v -> return v
    Nothing -> CM.fail $ traceSummary trace
  where
    FlowState mv _ trace = unFlow f cx emptyTrace

fromMaybe :: String -> Maybe a -> Flow s a
fromMaybe message m = case m of
  Nothing -> Flows.fail message
  Just v -> return v