CIDDecoder.hs

-- | Module      : MultiFormats.CID.Internal.CIDDecoder
--   Description : Parses CID bytes from a multibase encoded string
--   Copyright   : Zoey McBride (c) 2026
--   License     : AGPL-3.0-or-later
--   Maintainer  : zoeymcbride@mailbox.org
--   Stability   : experimental
module MultiFormats.CID.Internal.CIDDecoder (CIDDecoder (CIDDecoder)) where

import Data.ByteString (ByteString)
import MultiFormats.CID.Errors
import MultiFormats.CID.Internal.CIDVersion (isCIDv0Str)
import MultiFormats.CID.Parser
import MultiFormats.MultiBase (decodeCIDv0, decodeFromPrefix, hasValidPrefix)

-- | Implements decoding CID from String's base encoding.
newtype CIDDecoder = CIDDecoder ByteString

-- | Decodes a CID to bytes.
instance Parser CIDDecoder where
  parser str =
    let choosedecoder
          | null str = Left (InvalidData EmptyCID)
          | isCIDv0Str str = Right decodeCIDv0
          | hasValidPrefix str = Right decodeFromPrefix
          | otherwise = Left (InvalidEncoding UnknownBasePrefix)
     in choosedecoder >>= \decoder ->
          case decoder str of
            Nothing -> Left (InvalidEncoding ImproperDigit)
            Just bytes -> Right (CIDDecoder bytes)