{-# LANGUAGE OverloadedStrings #-}

module Utils where

import Control.Monad.IO.Class
import Data.List.Extra (stripSuffix)
import Data.Maybe (isJust)
import qualified Data.Text as T
import Text.Pandoc.Definition
import qualified Text.Pandoc.Walk

import Types

-- | A shortcut for `liftIO`.
io :: MonadIO m => IO a -> m a
io = liftIO

-- | A helper for throwing an error if something is `Nothing`
just :: String -> Maybe a -> a
just _ (Just val) = val
just err Nothing = error ("Missing: " ++ err)

-- | Test for whether something listy has a suffix
hasSuffix :: Eq a => [a] -> [a] -> Bool
hasSuffix s = isJust . stripSuffix s

-- | The same second as from arrows et al.
second :: (a -> b) -> (c, a) -> (c, b)
second f (a, b) = (a, f b)

-- | A pandoc walker for modifying the URLs.
walkURLs ::
     (FilePath -> Site FilePath)
  -> Text.Pandoc.Definition.Pandoc
  -> Site Text.Pandoc.Definition.Pandoc
walkURLs f = Text.Pandoc.Walk.walkM go
  where
    go (Link a i (u, t)) = do
      u' <- T.pack <$> f (T.unpack u)
      pure $ Link a i (u', t)
    go (Image a i (u, t)) = do
      u' <- T.pack <$> f (T.unpack u)
      pure $ Image a i (u', t)
    go x = pure x

-- | A pandoc walker for adding the local links to the headings (links are
-- appended and get a given class)
addHeadingLinks ::
     T.Text -> Text.Pandoc.Definition.Pandoc -> Text.Pandoc.Definition.Pandoc
addHeadingLinks cls = Text.Pandoc.Walk.walk go
  where
    go h@(Header lvl attr@(id, _, _) inlines) =
      Header
        lvl
        attr
        (inlines ++
         [Link ("", [cls], []) [Str "#"] ("#" <> id, "Link to this section")])
    go x = x

hasUriScheme :: String -> String -> Bool
hasUriScheme x = all id . zipWith (==) x . (++ ":")

unAbsolute :: String -> String
unAbsolute = dropWhile (== '/')