module Utils
  ( basename
  , errorsAndResults
  , escapeHTML
  , lookupMeta'
  , makeFullFilePath
  , sortByDate
  )
where

import           Data.Aeson                     ( toJSON
                                                , Value
                                                )
import           Data.List
import           Data.Ord
import qualified Data.Text                     as T
import           System.Directory
import           System.FilePath
import           Text.Pandoc

basename :: FilePath -> String
basename = dropExtension . takeFileName

errorsAndResults
  :: [(FilePath, Either PandocError a)] -> ([PandocError], [(FilePath, a)])
errorsAndResults xs =
  let errors  = [ error | result@(_, Left error) <- xs ]
      results = [ (path, a) | result@(path, Right a) <- xs ]
  in  (errors, results)

lookupMeta' :: String -> Meta -> T.Text
lookupMeta' key meta = case lookupMeta key meta of
  Just value -> renderMeta value
  Nothing    -> T.empty

makeFullFilePath :: FilePath -> FilePath -> IO FilePath
makeFullFilePath root path = makeAbsolute $ joinPath [root, path]

renderMeta :: MetaValue -> T.Text
renderMeta (MetaInlines meta) =
  case runPure $ writePlain (def Nothing) (Pandoc nullMeta [Plain meta]) of
    Left  err  -> T.empty
    Right text -> text

getDate :: Pandoc -> T.Text
getDate (Pandoc m _) = lookupMeta' "date" m

sortByDate :: [(FilePath, Pandoc)] -> [(FilePath, Pandoc)]
sortByDate = sortBy (flip (comparing $ getDate . snd))

escapeHTML :: String -> String
escapeHTML = concatMap f
 where
  f '>'  = "&gt;"
  f '<'  = "&lt;"
  f '&'  = "&amp;"
  f '\"' = "&quot;"
  f '\'' = "&#39;"
  f x    = [x]