{-# LANGUAGE TypeOperators, PolyKinds, DataKinds, TypeFamilies, UndecidableInstances, AllowAmbiguousTypes, TypeSynonymInstances, FlexibleInstances, ScopedTypeVariables, GADTs #-} module Propellor.Types.Target ( {- Target(..), Targeting(..), mkProperty, mkProperty', OuterTarget, ensureProperty, orProperty, target, UnixLike, unixLike, DebianOnly, debian, BuntishOnly, buntish, FreeBSDOnly, freeBSD, unionTargets, intersectTarget, -} ) where import Network.BSD (HostName) import Data.Typeable import Data.String import Data.List ----- DEMO ---------- -- Intentionally a type error! :) --foo :: Property (Targeting '[OSDebian, OSFreeBSD]) --foo = Property supportedos $ do -- ensureProperty supportedos jail -- where supportedos = unionTargets debian freeBSD {- bar :: Property (Targeting '[OSDebian, OSFreeBSD]) bar = aptinstall `orProperty` jail -} foo :: Property FreeBSDOnly foo = mkProperty' $ \t -> do ensureProperty t jail aptinstall :: Property DebianOnly aptinstall = mkProperty $ do return () jail :: Property (HasInfo :+: FreeBSDOnly) 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 | 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 DebianOnly = WithTypes '[Targeting OSDebian] type BuntishOnly = WithTypes '[Targeting OSBuntish] type FreeBSDOnly = WithTypes '[Targeting OSFreeBSD] type HasInfo = WithTypes '[WithInfo] data family WithTypes (x :: k) class Sing t where -- Constructor for a singleton WithTypes list. 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, to add HasInfo to the DebianOnly list: -- -- > HasInfo :+: DebianOnly -- -- 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`. Only properties whose -- PropTypes are a superset of the OuterPropTypes can be ensured. ensureProperty :: ((inner `NotSupersetTargets` outer) ~ CanCombineTargets) => OuterPropTypes outer -> Property inner -> IO () ensureProperty (OuterPropTypes outerproptypes) (Property innerproptypes a) = a {- -- | Changes the target of a property. -- -- This can only tighten the target list to contain fewer targets. target :: (combinedtarget ~ IntersectTarget oldtarget newtarget, CannotCombineTargets oldtarget newtarget combinedtarget ~ CanCombineTargets) => Targeting newtarget -> Property (Targeting oldtarget) -> Property (Targeting combinedtarget) target newtarget (Property oldtarget a) = Property (intersectTarget oldtarget newtarget) 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 (unionTargets ta tb) io where -- TODO pick with of ioa or iob to use based on final OS of -- system being run on. io = undefined -- | The union of two lists of Targets. unionTargets :: Targeting l1 -> Targeting l2 -> Targeting (UnionTarget l1 l2) unionTargets (Targeting l1) (Targeting l2) = Targeting $ nub $ l1 ++ l2 -- | The intersection between two lists of Targets. intersectTarget :: (r ~ IntersectTarget l1 l2, CannotCombineTargets l1 l2 r ~ CanCombineTargets) => Targeting l1 -> Targeting l2 -> Targeting r intersectTarget (Targeting l1) (Targeting l2) = Targeting $ nub $ filter (`elem` l2) l1 -} data CheckCombineTargets = CannotCombineTargets | CanCombineTargets {- -- | Detect intersection of two lists that don't have any common OS. -- -- 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 target in the subset must be in the superset. -- -- The name of this was chosen to make type errors a more understandable. type family NotSupersetTargets (superset :: [a]) (subset :: [a]) :: CheckCombineTargets type instance NotSupersetTargets superset '[] = 'CanCombineTargets type instance NotSupersetTargets superset (s ': rest) = If (ElemTarget s superset) (NotSupersetTargets superset rest) 'CannotCombineTargets {- -- | Type level intersection of lists of Targets type family IntersectTarget (list1 :: [a]) (list2 :: [a]) :: [a] type instance IntersectTarget '[] list2 = '[] type instance IntersectTarget (a ': rest) list2 = If (ElemTarget a list2 && Not (ElemTarget a rest)) (a ': IntersectTarget rest list2) (IntersectTarget rest list2) -- | 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) -- | Type level elem for Target type family ElemTarget (a :: Target) (list :: [Target]) :: Bool type instance ElemTarget a '[] = 'False type instance ElemTarget a (b ': bs) = EqTarget a b || ElemTarget a bs -- | Type level equality for Target -- -- This is a very clumsy implmentation, but it works back to ghc 7.6. type family EqTarget (a :: Target) (b :: Target) :: Bool type instance EqTarget OSDebian OSDebian = 'True type instance EqTarget OSBuntish OSBuntish = 'True type instance EqTarget OSFreeBSD OSFreeBSD = 'True type instance EqTarget OSDebian OSBuntish = 'False type instance EqTarget OSDebian OSFreeBSD = 'False type instance EqTarget OSBuntish OSDebian = 'False type instance EqTarget OSBuntish OSFreeBSD = 'False type instance EqTarget OSFreeBSD OSDebian = 'False type instance EqTarget OSFreeBSD OSBuntish = 'False -- More modern version if the combinatiorial explosion gets too bad later: -- -- type family EqTarget (a :: Target) (b :: Target) where -- EqTarget a a = True -- EqTarget 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