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{- Copyright © 2015 Benjamin Barenblat
This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>. -}
module Tangle (tangle) where
import Control.Exception (assert)
import Control.Monad (liftM)
import Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map
import Fragment (Fragment, isBlockCode, blockName, blockContents,
CodeOrReference(Code, Reference))
type FragmentGraph = Map String [CodeOrReference]
tangle :: [Fragment] -> Either String String
tangle fragments =
case filter isBlockCode fragments of
[] -> Right ""
codeBlocks@(root:_) ->
expandBlock (fragmentGraph codeBlocks) (blockName root)
fragmentGraph :: [Fragment] -> FragmentGraph
fragmentGraph frags =
Map.fromListWith (++) $
map (\block -> blockToPair $ assert (isBlockCode block) block) frags
where blockToPair frag = (blockName frag, blockContents frag)
expandBlock :: FragmentGraph -> String -> Either String String
expandBlock fragments name =
case Map.lookup name fragments of
Nothing -> Left $ "Desired node " ++ name ++ " not in fragment graph"
Just block -> concatMapM (expandBlockBody1 fragments) block
expandBlockBody1 :: FragmentGraph -> CodeOrReference -> Either String String
expandBlockBody1 _ (Code body) = Right body
expandBlockBody1 fragments (Reference name) = expandBlock fragments name
concatMapM :: Monad m => (a -> m [b]) -> [a] -> m [b]
concatMapM f lists = liftM concat $ mapM f lists
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