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{-# LANGUAGE OverloadedStrings #-}
-- | Paths are horrible, so they have their own module now.
-- I just hope you are running this on some kind of Unix
module Paths where
import Data.Text (Text)
import qualified Data.Text as T
import System.FilePath (splitPath)
import System.FilePath.Posix ((</>))
import Text.Regex.TDFA
import Util (PrettyPrint (prettyprint))
-- | a normalised path: a number of "upwards" steps, and
-- a path without any . or .. in it. Also possibly a
-- fragment, mostly for map links.
data RelPath = Path Int Text (Maybe Text)
deriving (Show, Eq, Ord)
-- | horrible regex parsing for filepaths that is hopefully kinda safe
parsePath :: Text -> Maybe RelPath
parsePath text =
if rest =~ ("^([^/]*[^\\./]/)*[^/]*[^\\./]$" :: Text) :: Bool
then Just $ Path up path fragment
else Nothing
where
(_, prefix, rest, _) =
text =~ ("^((\\.|\\.\\.)/)*" :: Text) :: (Text, Text, Text, [Text])
-- how many steps upwards in the tree?
up = length . filter (".." ==) . T.splitOn "/" $ prefix
parts = T.splitOn "#" rest
path = head parts
fragment = if length parts >= 2
then Just $ T.concat $ tail parts -- TODO!
else Nothing
instance PrettyPrint RelPath where
prettyprint (Path up rest frag) = ups <> rest <> fragment
where ups = T.concat $ replicate up "../"
fragment = maybe mempty ("#" <>) frag
-- | Normalises a path.
--
-- It takes a `prefix`, and will "truncate" the .. operator
-- at the end of the prefix, i.e. it will never return paths
-- that lie (naïvely) outside of the prefix.
normalise :: FilePath -> RelPath -> FilePath
normalise prefix (Path 0 path _) = prefix </> T.unpack path
normalise prefix (Path i path _) =
concat (take (length dirs - i) dirs) </> T.unpack path
where dirs = splitPath prefix
normaliseWithFrag :: FilePath -> RelPath -> FilePath
normaliseWithFrag prefix (Path i path frag) =
normalise prefix (Path (i+1) path frag) <> T.unpack (maybe mempty ("#" <>) frag)
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