Resolving trees with maps

Maps.hs

module Maps where

import qualified Data.Maybe      as Mb
import qualified Data.Map.Strict as M

data Plugin
  = Plugin { pName :: String, pDependencies :: [String] }
  deriving (Eq, Show)

plugins :: [Plugin]
plugins
  = [ Plugin "thing" ["thang", "thung"]
    , Plugin "thung" ["thang"]
    , Plugin "thang" ["foo", "bar"]
    , Plugin "foo" []
    , Plugin "bar" ["baz"]
    , Plugin "baz" []
    ]

data ResolvedPlugin
  = ResolvedPlugin { rpName :: String, rpDependencies :: [ResolvedPlugin] }
  deriving (Eq, Show)

resolvePlugins :: [Plugin] -> [ResolvedPlugin]
resolvePlugins ps
  = map snd (M.toList rpm)
  where
    pm  = M.fromList (map (\p -> (pName p, p)) ps)
    rpm = M.map (resolvePlugin rpm) pm

resolvePlugin :: M.Map String ResolvedPlugin -> Plugin -> ResolvedPlugin
resolvePlugin m (Plugin name deps)
  = ResolvedPlugin name (Mb.catMaybes (map (flip M.lookup m) deps))