{-# LANGUAGE TypeOperators, PolyKinds, DataKinds, TypeFamilies, UndecidableInstances, AllowAmbiguousTypes, TypeSynonymInstances, FlexibleInstances, ScopedTypeVariables, GADTs #-} module Propellor.Types.Target ( Property(..), mkProperty, mkProperty', OS(..), PropType(..), UnixLike, Debian, Buntish, FreeBSD, HasInfo, (:+:), OuterPropTypes, ensureProperty, Sing, WithTypes, ) where import Network.BSD (HostName) import Data.Typeable import Data.String import Data.List ----- DEMO ---------- foo :: Property (HasInfo :+: FreeBSD) foo = mkProperty' $ \t -> do ensureProperty t jail {- bar :: Property (Targeting '[OSDebian, OSFreeBSD]) bar = aptinstall `orProperty` jail -} aptinstall :: Property Debian aptinstall = mkProperty $ do return () jail :: Property FreeBSD jail = mkProperty $ do return () ----- END DEMO ---------- data Property proptypes = Property proptypes (IO ()) mkProperty :: Sing l => IO () -> Property (WithTypes l) mkProperty = mkProperty' . const mkProperty' :: Sing l => (OuterPropTypes l -> IO ()) -> Property (WithTypes l) mkProperty' a = let p = Property sing (a (outerPropTypes p)) in p data OS = OSDebian | OSBuntish -- ^ A well-known Debian derivative founded by a space tourist. The actual name of this distribution is not used in Propellor per | OSFreeBSD deriving (Show, Eq) data PropType = Targeting OS -- ^ A target OS of a Property | WithInfo -- ^ Indicates that a Property has associated Info deriving (Show, Eq) -- | Any unix-like system type UnixLike = WithTypes '[Targeting OSDebian, Targeting OSBuntish, Targeting OSFreeBSD] type Debian = WithTypes '[Targeting OSDebian] type Buntish = WithTypes '[Targeting OSBuntish] type FreeBSD = WithTypes '[Targeting OSFreeBSD] -- | Used to indicate that a Property adds Info to the Host where it's used. type HasInfo = WithTypes '[WithInfo] -- | A family of type-level lists of [`PropType`] data family WithTypes (x :: k) -- | Singletons class Sing t where sing :: WithTypes t data instance WithTypes (x :: [k]) where Nil :: WithTypes '[] Cons :: WithTypes x -> WithTypes xs -> WithTypes (x ': xs) instance (Sing x, Sing xs) => Sing (x ': xs) where sing = Cons sing sing instance Sing '[] where sing = Nil -- This boilerplatw would not be needed if the singletons library were -- used. However, we're targeting too old a version of ghc to use it yet. data instance WithTypes (x :: PropType) where OSDebianS :: WithTypes ('Targeting OSDebian) OSBuntishS :: WithTypes ('Targeting OSBuntish) OSFreeBSDS :: WithTypes ('Targeting OSFreeBSD) WithInfoS :: WithTypes 'WithInfo instance Sing ('Targeting OSDebian) where sing = OSDebianS instance Sing ('Targeting OSBuntish) where sing = OSBuntishS instance Sing ('Targeting OSFreeBSD) where sing = OSFreeBSDS instance Sing 'WithInfo where sing = WithInfoS -- | Convenience type operator to combine two `WithTypes` lists. -- -- For example: -- -- > HasInfo :+: Debian -- -- Which is shorthand for this type: -- -- > WithTypes '[WithInfo, Targeting OSDebian] type family a :+: b :: ab type instance (WithTypes a) :+: (WithTypes b) = WithTypes (Concat a b) type family Concat (list1 :: [a]) (list2 :: [a]) :: [a] type instance Concat '[] bs = bs type instance Concat (a ': as) bs = a ': (Concat as bs) newtype OuterPropTypes l = OuterPropTypes (WithTypes l) outerPropTypes :: Property (WithTypes l) -> OuterPropTypes l outerPropTypes (Property proptypes _) = OuterPropTypes proptypes -- | Use `mkProperty''` to get the `OuterPropTypes`. For example: -- -- > foo = Property Debian -- > foo = mkProperty' $ \t -> do -- > ensureProperty t (aptInstall "foo") -- -- The type checker will prevent using ensureProperty with a property -- that does not support the target OSes needed by the OuterPropTypes. -- In the example above, aptInstall must support Debian. -- -- The type checker will also prevent using ensureProperty with a property -- with HasInfo in its PropTypes. Doing so would cause the info associated -- with the property to be lost. ensureProperty :: ((Targets inner `NotSuperset` Targets outer) ~ CanCombineTargets , CannotUseEnsurePropertyWithInfo inner ~ True ) => OuterPropTypes outer -> Property (WithTypes inner) -> IO () ensureProperty (OuterPropTypes outerproptypes) (Property innerproptypes a) = a -- The name of this was chosen to make type errors a more understandable. type family CannotUseEnsurePropertyWithInfo (l :: [a]) :: Bool type instance CannotUseEnsurePropertyWithInfo '[] = 'True type instance CannotUseEnsurePropertyWithInfo (t ': ts) = Not (t `EqT` WithInfo) && CannotUseEnsurePropertyWithInfo ts -- | Tightens the PropType list of a Property, to contain fewer targets. -- -- Anything else in the PropType list is passed through unchanged. tightenTargets :: ( combined ~ Concat (NonTargets old) (Intersect (Targets old) newtargets) , CannotCombineTargets old new combined ~ CanCombineTargets ) => Targeting newtargets -> Property (WithTypes old) -> Property (WithTypes combined) tightenTargets _ (Property old a) = Property sing a {- -- | Picks one of the two input properties to use, -- depending on the targeted OS. -- -- If both input properties support the targeted OS, then the -- first will be used. orProperty :: Property (Targeting a) -> Property (Targeting b) -> Property (Targeting (UnionTarget a b)) orProperty a@(Property ta ioa) b@(Property tb iob) = Property sing io where -- TODO pick with of ioa or iob to use based on final OS of -- system being run on. io = undefined -- | Type level union of lists of Targets type family UnionTarget (list1 :: [a]) (list2 :: [a]) :: [a] type instance UnionTarget '[] list2 = list2 type instance UnionTarget (a ': rest) list2 = If (ElemTarget a list2 || ElemTarget a rest) (UnionTarget rest list2) (a ': UnionTarget rest list2) -} data CheckCombineTargets = CannotCombineTargets | CanCombineTargets -- | Detect intersection of two lists that don't have any common targets. -- -- The name of this was chosen to make type errors a more understandable. type family CannotCombineTargets (list1 :: [a]) (list2 :: [a]) (listr :: [a]) :: CheckCombineTargets type instance CannotCombineTargets l1 l2 '[] = 'CannotCombineTargets type instance CannotCombineTargets l1 l2 (a ': rest) = 'CanCombineTargets -- | Every item in the subset must be in the superset. -- -- The name of this was chosen to make type errors a more understandable. type family NotSuperset (superset :: [a]) (subset :: [a]) :: CheckCombineTargets type instance NotSuperset superset '[] = 'CanCombineTargets type instance NotSuperset superset (s ': rest) = If (Elem s superset) (NotSuperset superset rest) 'CannotCombineTargets type family IsTarget (a :: t) :: Bool type instance IsTarget (Targeting a) = True type instance IsTarget WithInfo = False type family Targets (l :: [a]) :: [a] type instance Targets '[] = '[] type instance Targets (x ': xs) = If (IsTarget x) (x ': Targets xs) (Targets xs) type family NonTargets (l :: [a]) :: [a] type instance NonTargets '[] = '[] type instance NonTargets (x ': xs) = If (IsTarget x) (Targets xs) (x ': Targets xs) -- | Type level elem type family Elem (a :: t) (list :: [t]) :: Bool type instance Elem a '[] = 'False type instance Elem a (b ': bs) = EqT a b || Elem a bs -- | Type level intersection. Duplicate list items are eliminated. type family Intersect (list1 :: [a]) (list2 :: [a]) :: [a] type instance Intersect '[] list2 = '[] type instance Intersect (a ': rest) list2 = If (Elem a list2 && Not (Elem a rest)) (a ': Intersect rest list2) (Intersect rest list2) -- | Type level equality -- -- This is a very clumsy implmentation, but it works back to ghc 7.6. type family EqT (a :: t) (b :: t) :: Bool type instance EqT (Targeting a) (Targeting b) = EqT a b type instance EqT WithInfo WithInfo = 'True type instance EqT WithInfo (Targeting b) = 'False type instance EqT (Targeting a) WithInfo = 'False type instance EqT OSDebian OSDebian = 'True type instance EqT OSBuntish OSBuntish = 'True type instance EqT OSFreeBSD OSFreeBSD = 'True type instance EqT OSDebian OSBuntish = 'False type instance EqT OSDebian OSFreeBSD = 'False type instance EqT OSBuntish OSDebian = 'False type instance EqT OSBuntish OSFreeBSD = 'False type instance EqT OSFreeBSD OSDebian = 'False type instance EqT OSFreeBSD OSBuntish = 'False -- More modern version if the combinatiorial explosion gets too bad later: -- -- type family Eq (a :: PropType) (b :: PropType) where -- Eq a a = True -- Eq a b = False -- | An equivilant to the following is in Data.Type.Bool in -- modern versions of ghc, but is included here to support ghc 7.6. type family If (cond :: Bool) (tru :: a) (fls :: a) :: a type instance If 'True tru fls = tru type instance If 'False tru fls = fls type family (a :: Bool) || (b :: Bool) :: Bool type instance 'False || 'False = 'False type instance 'True || 'True = 'True type instance 'True || 'False = 'True type instance 'False || 'True = 'True type family (a :: Bool) && (b :: Bool) :: Bool type instance 'False && 'False = 'False type instance 'True && 'True = 'True type instance 'True && 'False = 'False type instance 'False && 'True = 'False type family Not (a :: Bool) :: Bool type instance Not 'False = 'True type instance Not 'True = 'False