module Distribution.Types.DependencyMap (
    DependencyMap,
    toDepMap,
    fromDepMap,
    constrainBy,
) where

import Distribution.Compat.Prelude
import Prelude ()

import Distribution.Types.Dependency
import Distribution.Types.LibraryName
import Distribution.Types.PackageName
import Distribution.Types.PackageVersionConstraint
import Distribution.Version

import qualified Data.Map.Lazy as Map

-- | A map of dependencies.  Newtyped since the default monoid instance is not
--   appropriate.  The monoid instance uses 'intersectVersionRanges'.
newtype DependencyMap = DependencyMap { unDependencyMap :: Map PackageName (VersionRange, NonEmptySet LibraryName) }
  deriving (Show, Read)

instance Monoid DependencyMap where
    mempty = DependencyMap Map.empty
    mappend = (<>)

instance Semigroup DependencyMap where
    (DependencyMap a) <> (DependencyMap b) =
        DependencyMap (Map.unionWith intersectVersionRangesAndJoinComponents a b)

intersectVersionRangesAndJoinComponents :: (VersionRange, NonEmptySet LibraryName)
                                        -> (VersionRange, NonEmptySet LibraryName)
                                        -> (VersionRange, NonEmptySet LibraryName)
intersectVersionRangesAndJoinComponents (va, ca) (vb, cb) =
  (intersectVersionRanges va vb, ca <> cb)

toDepMap :: [Dependency] -> DependencyMap
toDepMap ds =
  DependencyMap $ Map.fromListWith intersectVersionRangesAndJoinComponents [ (p,(vr,cs)) | Dependency p vr cs <- ds ]

fromDepMap :: DependencyMap -> [Dependency]
fromDepMap m = [ Dependency p vr cs | (p,(vr,cs)) <- Map.toList (unDependencyMap m) ]

-- Apply extra constraints to a dependency map.
-- Combines dependencies where the result will only contain keys from the left
-- (first) map.  If a key also exists in the right map, both constraints will
-- be intersected.
constrainBy
    :: DependencyMap
    -> [PackageVersionConstraint]
    -> DependencyMap
constrainBy = foldl' tightenConstraint where
    tightenConstraint (DependencyMap l) (PackageVersionConstraint pn vr) = DependencyMap $
        case Map.lookup pn l of
            Nothing        -> l
            Just (vr', cs) -> Map.insert pn (intersectVersionRanges vr' vr, cs) l
