module Unified (unified) where

import Diff
import Patch
import Syntax
import Term
import Control.Arrow
import Control.Monad.Free
import Control.Comonad.Cofree
import Data.List hiding (foldl)
import qualified Data.Map as Map
import Rainbow

unified :: Diff a Info -> String -> String -> IO ByteString
unified diff before after = do
  renderer <- byteStringMakerFromEnvironment
  return . mconcat . chunksToByteStrings renderer . pure . fst $ iter g mapped where
    mapped = fmap (unifiedPatch &&& range) diff
    g (Annotated (_, info) syntax) = f info syntax
    f (Info range _) (Leaf _) = (substring range after, Just range)
    f (Info range _) (Indexed i) = (unifiedRange range i after, Just range)
    f (Info range _) (Fixed f) = (unifiedRange range f after, Just range)
    f (Info range _) (Keyed k) = (unifiedRange range (sort $ snd <$> Map.toList k) after, Just range)

    unifiedPatch :: Patch (Term a Info) -> Chunk String
    unifiedPatch patch = (beforeChunk & fore red & bold) <> (afterChunk & fore green & bold) where
      beforeChunk = maybe (chunk "") (change "-" . unifiedTerm before) $ Patch.before patch
      afterChunk = maybe (chunk "") (change "+" . unifiedTerm after) $ Patch.after patch

    unifiedTerm :: String -> Term a Info -> Chunk String
    unifiedTerm source term = fst $ cata f term

    unifiedRange :: Range -> [(Chunk String, Maybe Range)] -> String -> Chunk String
    unifiedRange range children source = out <> substring Range { start = previous, end = end range } after where
      (out, previous) = foldl accumulateContext (chunk "", start range) children
      accumulateContext (out, previous) (child, Just range) = (mconcat [ out, substring Range { start = previous, end = start range } source, child ], end range)
      accumulateContext (out, previous) (child, _) = (out <> child, previous)

substring :: Range -> String -> Chunk String
substring range = chunk . take (end range) . drop (start range)

range :: Patch (Term a Info) -> Maybe Range
range patch = range . extract <$> after patch where
  extract (annotation :< _) = annotation
  range (Info range _) = range

change :: String -> Chunk String -> Chunk String
change bound content = mconcat [ chunk "{", chunk bound, content, chunk bound, chunk "}" ]

instance Ord Range where
  a <= b = start a <= start b