module Nuthatch.Paths
  ( validateRelativePath
  , buildObjectKey
  , listCacheAncestorPrefixes
  , encodeUserId
  , basename
  ) where

import           Crypto.Hash (Digest, SHA256, hash)
import qualified Data.ByteArray as BA
import qualified Data.ByteString as BS
import qualified Data.ByteString.Base16 as B16
import           Data.Text (Text)
import qualified Data.Text as T
import qualified Data.Text.Encoding as TE
import           Nuthatch.Types

buildObjectKey :: Root -> UserId -> RelativePath -> ObjectKey
buildObjectKey root uid (RelativePath path) =
  ObjectKey $ case root of
    Personal -> "users/" <> unUserId uid <> "/" <> path
    Shared   -> "shared/" <> path

listCacheAncestorPrefixes :: RelativePath -> [Text]
listCacheAncestorPrefixes (RelativePath path) =
  let segs = filter (not . T.null) (T.splitOn "/" path)
  in case segs of
       [] -> [""]
       _  -> "" : init (scanl1 (\a b -> a <> "/" <> b) segs)

encodeUserId :: Text -> Text -> UserId
encodeUserId iss sub =
  let material = TE.encodeUtf8 (iss <> "\0" <> sub)
      digest = hash material :: Digest SHA256
      hex = B16.encode (BS.pack (BA.unpack digest))
  in UserId (TE.decodeUtf8 hex)

basename :: RelativePath -> Text
basename (RelativePath path) =
  case reverse (T.splitOn "/" path) of
    (x : _) -> x
    []      -> path