{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}

module FormatDocument
  ( program,
    loadFragment,
    markdownToPandoc,
  )
where

import Core.Program
import Core.System
import Core.Text
import qualified Data.Text as T (Text)
import qualified Data.Text.IO as T
import PandocToMarkdown
import System.Directory (getFileSize, renameFile)
import System.IO (IOMode (..), withFile)
import Text.Pandoc
  ( Extension (..),
    Extensions,
    Pandoc,
    ReaderOptions (readerExtensions),
    def,
    disableExtension,
    pandocExtensions,
    readMarkdown,
    runIOorExplode,
  )

program :: Program None ()
program = do
  event "Identify document fragment"
  file <- getFragmentName

  event "Load to Pandoc internal representation"
  parsed <- loadFragment file

  event "Write to Markdown format"
  writeResult file parsed

  event "Complete"

getFragmentName :: Program None FilePath
getFragmentName = do
  params <- getCommandLine

  let fragment = case lookupArgument "document" params of
        Nothing -> error "invalid"
        Just file -> file
  return fragment

loadFragment :: FilePath -> Program None Pandoc
loadFragment file =
  liftIO $ do
    contents <- T.readFile file
    markdownToPandoc contents

--
-- Unlike the render use case, here we suppress certain
-- options which mess up the ASCII form of the source documents
--
markdownToPandoc :: T.Text -> IO Pandoc
markdownToPandoc contents =
  let disableFrom :: Extensions -> [Extension] -> Extensions
      disableFrom extensions list = foldr disableExtension extensions list
      readingOptions =
        def
          { readerExtensions =
              disableFrom
                pandocExtensions
                [ Ext_implicit_figures,
                  Ext_shortcut_reference_links,
                  Ext_smart
                ]
          }
   in do
        runIOorExplode $ do
          readMarkdown readingOptions contents

data Inplace = Inplace | Console

writeResult :: FilePath -> Pandoc -> Program None ()
writeResult file doc =
  let contents' = pandocToMarkdown doc
      result = file ++ "~tmp"
   in do
        params <- getCommandLine

        let mode = case lookupOptionFlag "inplace" params of
              Just False -> error "Invalid State"
              Just True -> Inplace
              Nothing -> Console

        case mode of
          Inplace -> liftIO $ do
            withFile result WriteMode $ \handle ->
              hWrite handle contents'

            size <- getFileSize result
            if size == 0
              then error "Zero content, not overwriting"
              else renameFile result file
          Console -> liftIO $ do
            hWrite stdout contents'