module Renderer (Renderer, Output(..), concatOutputs, toSummaryKey, Format(..)) where

import Data.Aeson (Value, encode)
import Data.Functor.Both
import Data.Map as Map hiding (null)
import Data.Text.Encoding (encodeUtf8)
import qualified Data.ByteString as B
import Data.Functor.Listable
import Prologue
import Source (SourceBlob)
import Syntax
import Diff

-- | A function that will render a diff, given the two source blobs.
type Renderer annotation = Both SourceBlob -> Diff (Syntax Text) annotation -> Output

-- | The available types of diff rendering.
data Format = Split | Patch | JSON | Summary | SExpression | TOC
  deriving (Show)

data Output = SplitOutput Text | PatchOutput Text | JSONOutput (Map Text Value) | SummaryOutput (Map Text (Map Text [Value])) | SExpressionOutput ByteString | TOCOutput (Map Text (Map Text [Value]))
  deriving (Show)

-- Returns a key representing the filename. If the filenames are different,
-- return 'before -> after'.
toSummaryKey :: Both FilePath -> Text
toSummaryKey = runBothWith $ \before after ->
  toS $ case (before, after) of
    ("", after) -> after
    (before, "") -> before
    (before, after) | before == after -> after
    (before, after) | not (null before) && not (null after) -> before <> " -> " <> after
    (_, _) -> mempty

-- Concatenates a list of 'Output' depending on the output type.
-- For JSON, each file output is merged since they're uniquely keyed by filename.
-- For Summaries, each file output is merged into one 'Object' consisting of lists of
-- changes and errors.
-- Split and Patch output is appended together with newlines.
concatOutputs :: [Output] -> ByteString
concatOutputs list | isJSON list = toS . encode $ concatJSON list
  where
    concatJSON :: [Output] -> Map Text Value
    concatJSON (JSONOutput hash : rest) = Map.union hash (concatJSON rest)
    concatJSON _ = mempty
concatOutputs list | isSummary list = toS . encode $ concatSummaries list
  where
    concatSummaries :: [Output] -> Map Text (Map Text [Value])
    concatSummaries (SummaryOutput hash : rest) = Map.unionWith (Map.unionWith (<>)) hash (concatSummaries rest)
    concatSummaries (TOCOutput hash : rest) = Map.unionWith (Map.unionWith (<>)) hash (concatSummaries rest)
    concatSummaries _ = mempty
concatOutputs list | isByteString list = B.intercalate "\n" (toByteString <$> list)
concatOutputs list | isText list = B.intercalate "\n" (encodeUtf8 . toText <$> list)
concatOutputs _ = mempty

isJSON :: [Output] -> Bool
isJSON (JSONOutput _ : _) = True
isJSON _ = False

isSummary :: [Output] -> Bool
isSummary (SummaryOutput _ : _) = True
isSummary (TOCOutput _ : _) = True
isSummary _ = False

isText :: [Output] -> Bool
isText (SplitOutput _ : _) = True
isText (PatchOutput _ : _) = True
isText _ = False

toText :: Output -> Text
toText (SplitOutput text) = text
toText (PatchOutput text) = text
toText _ = mempty

isByteString :: [Output] -> Bool
isByteString (SExpressionOutput _ : _) = True
isByteString _ = False

toByteString :: Output -> ByteString
toByteString (SExpressionOutput text) = text
toByteString _ = B.empty


instance Listable Format where
  tiers = cons0 Split
       \/ cons0 Patch
       \/ cons0 JSON
       \/ cons0 Summary
       \/ cons0 SExpression
       \/ cons0 TOC