{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE FlexibleInstances #-}
module Distribution.Solver.Types.Progress
    ( Progress(..)
    , foldProgress
    , step
    ) where

import Prelude ()
import Distribution.Solver.Compat.Prelude

-- | A type to represent the unfolding of an expensive long running
-- calculation that may fail. We may get intermediate steps before the final
-- result which may be used to indicate progress and\/or logging messages.
--
data Progress step fail done = Step step (Progress step fail done)
                             | Fail fail
                             | Done done
  deriving ((forall a b.
 (a -> b) -> Progress step fail a -> Progress step fail b)
-> (forall a b. a -> Progress step fail b -> Progress step fail a)
-> Functor (Progress step fail)
forall a b. a -> Progress step fail b -> Progress step fail a
forall a b.
(a -> b) -> Progress step fail a -> Progress step fail b
forall step fail a b.
a -> Progress step fail b -> Progress step fail a
forall step fail a b.
(a -> b) -> Progress step fail a -> Progress step fail b
forall (f :: * -> *).
(forall a b. (a -> b) -> f a -> f b)
-> (forall a b. a -> f b -> f a) -> Functor f
$cfmap :: forall step fail a b.
(a -> b) -> Progress step fail a -> Progress step fail b
fmap :: forall a b.
(a -> b) -> Progress step fail a -> Progress step fail b
$c<$ :: forall step fail a b.
a -> Progress step fail b -> Progress step fail a
<$ :: forall a b. a -> Progress step fail b -> Progress step fail a
Functor)

step :: step -> Progress step fail ()
step :: forall step fail. step -> Progress step fail ()
step step
s = step -> Progress step fail () -> Progress step fail ()
forall step fail done.
step -> Progress step fail done -> Progress step fail done
Step step
s (() -> Progress step fail ()
forall step fail done. done -> Progress step fail done
Done ())

-- | Consume a 'Progress' calculation. Much like 'foldr' for lists but with two
-- base cases, one for a final result and one for failure.
--
-- Eg to convert into a simple 'Either' result use:
--
-- > foldProgress (flip const) Left Right
--
foldProgress :: (step -> a -> a) -> (fail -> a) -> (done -> a)
             -> Progress step fail done -> a
foldProgress :: forall step a fail done.
(step -> a -> a)
-> (fail -> a) -> (done -> a) -> Progress step fail done -> a
foldProgress step -> a -> a
step' fail -> a
fail' done -> a
done' = Progress step fail done -> a
fold
  where fold :: Progress step fail done -> a
fold (Step step
s Progress step fail done
p) = step -> a -> a
step' step
s (Progress step fail done -> a
fold Progress step fail done
p)
        fold (Fail fail
f)   = fail -> a
fail' fail
f
        fold (Done done
r)   = done -> a
done' done
r

instance Monad (Progress step fail) where
  return :: forall a. a -> Progress step fail a
return   = a -> Progress step fail a
forall a. a -> Progress step fail a
forall (f :: * -> *) a. Applicative f => a -> f a
pure
  Progress step fail a
p >>= :: forall a b.
Progress step fail a
-> (a -> Progress step fail b) -> Progress step fail b
>>= a -> Progress step fail b
f  = (step -> Progress step fail b -> Progress step fail b)
-> (fail -> Progress step fail b)
-> (a -> Progress step fail b)
-> Progress step fail a
-> Progress step fail b
forall step a fail done.
(step -> a -> a)
-> (fail -> a) -> (done -> a) -> Progress step fail done -> a
foldProgress step -> Progress step fail b -> Progress step fail b
forall step fail done.
step -> Progress step fail done -> Progress step fail done
Step fail -> Progress step fail b
forall step fail done. fail -> Progress step fail done
Fail a -> Progress step fail b
f Progress step fail a
p

instance MonadFail (Progress step String) where
  fail :: forall a. String -> Progress step String a
fail = String -> Progress step String a
forall step fail done. fail -> Progress step fail done
Fail

instance Applicative (Progress step fail) where
  pure :: forall a. a -> Progress step fail a
pure a
a  = a -> Progress step fail a
forall step fail done. done -> Progress step fail done
Done a
a
  Progress step fail (a -> b)
p <*> :: forall a b.
Progress step fail (a -> b)
-> Progress step fail a -> Progress step fail b
<*> Progress step fail a
x = (step -> Progress step fail b -> Progress step fail b)
-> (fail -> Progress step fail b)
-> ((a -> b) -> Progress step fail b)
-> Progress step fail (a -> b)
-> Progress step fail b
forall step a fail done.
(step -> a -> a)
-> (fail -> a) -> (done -> a) -> Progress step fail done -> a
foldProgress step -> Progress step fail b -> Progress step fail b
forall step fail done.
step -> Progress step fail done -> Progress step fail done
Step fail -> Progress step fail b
forall step fail done. fail -> Progress step fail done
Fail ((a -> b) -> Progress step fail a -> Progress step fail b
forall a b.
(a -> b) -> Progress step fail a -> Progress step fail b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
`fmap` Progress step fail a
x) Progress step fail (a -> b)
p

instance Monoid fail => Alternative (Progress step fail) where
  empty :: forall a. Progress step fail a
empty   = fail -> Progress step fail a
forall step fail done. fail -> Progress step fail done
Fail fail
forall a. Monoid a => a
mempty
  Progress step fail a
p <|> :: forall a.
Progress step fail a
-> Progress step fail a -> Progress step fail a
<|> Progress step fail a
q = (step -> Progress step fail a -> Progress step fail a)
-> (fail -> Progress step fail a)
-> (a -> Progress step fail a)
-> Progress step fail a
-> Progress step fail a
forall step a fail done.
(step -> a -> a)
-> (fail -> a) -> (done -> a) -> Progress step fail done -> a
foldProgress step -> Progress step fail a -> Progress step fail a
forall step fail done.
step -> Progress step fail done -> Progress step fail done
Step (Progress step fail a -> fail -> Progress step fail a
forall a b. a -> b -> a
const Progress step fail a
q) a -> Progress step fail a
forall step fail done. done -> Progress step fail done
Done Progress step fail a
p