{-# LANGUAGE OverloadedStrings #-}

import Data.Text (pack,unpack,Text)

import Text.Pandoc.Builder
import Text.Pandoc
import Text.Pandoc.Walk

import System.Environment (getArgs)

purely :: (b -> PandocPure a) -> b -> a
purely f = either (error . show) id . runPure . f

latex :: Text -> Pandoc
latex = purely $ readLaTeX def{
                   readerExtensions = getDefaultExtensions "latex" }

data Section = Section
  { level :: Int
  , attr  :: String
  , title :: String
  }

createSections :: Pandoc -> [Section]
createSections = query mkSec
  where mkSec (Header n _ inline) = [ Section
               { level=n
               ,  attr=""
               , title=getPlain inline
               }]
        mkSec _                   = []

getPlain :: [Inline] -> String
getPlain [] = ""
getPlain (x:xs) = stripeFrom x <> getPlain xs
  where stripeFrom (Str         strs  ) = unpack   strs
        stripeFrom (Code _      strs  ) = unpack   strs
        stripeFrom (Math _      strs  ) = unpack   strs
        stripeFrom (RawInline _ strs  ) = unpack   strs
        stripeFrom (Emph        strs  ) = getPlain strs
        stripeFrom (Underline   strs  ) = getPlain strs
        stripeFrom (Strong      strs  ) = getPlain strs
        stripeFrom (Strikeout   strs  ) = getPlain strs
        stripeFrom (Superscript strs  ) = getPlain strs
        stripeFrom (Subscript   strs  ) = getPlain strs
        stripeFrom (SmallCaps   strs  ) = getPlain strs
        stripeFrom (Quoted _    strs  ) = getPlain strs
        stripeFrom (Cite _      strs  ) = getPlain strs
        stripeFrom (Span _      strs  ) = getPlain strs
        stripeFrom (Link _      strs _) = getPlain strs
        stripeFrom (Image _     strs _) = getPlain strs
        stripeFrom Space                = " "
        stripeFrom _                    = ""


main :: IO ()
main = do
    (fileName:_) <- getArgs
    src <- readFile fileName
    let secs = createSections $ latex $ pack src
    putStrLn $ printResult $ getContents $ secs
    where getLevel (Section n _ str) = n
          getLevels = map getLevel
          getTitle (Section n attr str) = attr <> (show n) <> resetColor <> " " <> str
          diffl1 xs = zipWith (-) xs (0:xs)
          getColor n = if n>1 then boldRed else boldGreen
          boldRed    = "\x1b[1;31m"
          boldGreen  = "\x1b[1;32m"
          resetColor = "\x1b[0m"
          convertPretty (k, (Section n _ str)) = Section n (getColor k) str
          getContents sec = map convertPretty $ zip (diffl1 $ getLevels $ sec) sec
          printResult = unlines . map getTitle