{-# LANGUAGE OverloadedStrings #-}

{-

Copyright (C) 2014-2017 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program; if not, write to the Free Software

Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

-}

{- |

   Module      : Text.Pandoc.Readers.Org.Shared

   Copyright   : Copyright (C) 2014-2017 Albert Krewinkel

   License     : GNU GPL, version 2 or above

   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>

Utility functions used in other Pandoc Org modules.

-}

module Text.Pandoc.Readers.Org.Shared

  ( cleanLinkString

  , isImageFilename

  , originalLang

  , translateLang

  ) where

import Data.Char (isAlphaNum)

import Data.List (isPrefixOf, isSuffixOf)

-- | Check whether the given string looks like the path to of URL of an image.

isImageFilename :: String -> Bool

isImageFilename filename =

  any (\x -> ('.':x)  `isSuffixOf` filename) imageExtensions &&

  (any (\x -> (x ++ "://") `isPrefixOf` filename) protocols ||

   ':' `notElem` filename)

 where

   imageExtensions = [ "jpeg" , "jpg" , "png" , "gif" , "svg" ]

   protocols = [ "file", "http", "https" ]

-- | Cleanup and canonicalize a string describing a link.  Return @Nothing@ if

-- the string does not appear to be a link.

cleanLinkString :: String -> Maybe String

cleanLinkString s =

  case s of

    '/':_                  -> Just $ "file://" ++ s  -- absolute path

    '.':'/':_              -> Just s                 -- relative path

    '.':'.':'/':_          -> Just s                 -- relative path

    -- Relative path or URL (file schema)

    'f':'i':'l':'e':':':s' -> Just $ if "//" `isPrefixOf` s' then s else s'

    _                      | isUrl s            -> Just s                 -- URL

    _                      -> Nothing

 where

   isUrl :: String -> Bool

   isUrl cs =

     let (scheme, path) = break (== ':') cs

     in all (\c -> isAlphaNum c || c `elem` (".-"::String)) scheme

          && not (null path)

-- | Creates an key-value pair marking the original language name specified for

-- a piece of source code.

-- | Creates an key-value attributes marking the original language name

-- specified for a piece of source code.

originalLang :: String -> [(String, String)]

originalLang lang =

  let transLang = translateLang lang

  in if transLang == lang

     then []

     else [("org-language", lang)]

-- | Translate from Org-mode's programming language identifiers to those used

-- by Pandoc.  This is useful to allow for proper syntax highlighting in

-- Pandoc output.

translateLang :: String -> String

translateLang cs =

  case cs of

    "C"          -> "c"

    "C++"        -> "cpp"

    "emacs-lisp" -> "commonlisp" -- emacs lisp is not supported

    "js"         -> "javascript"

    "lisp"       -> "commonlisp"

    "R"          -> "r"

    "sh"         -> "bash"

    "sqlite"     -> "sql"

    _            -> cs