{-# LANGUAGE OverloadedStrings #-}

module Data.SMTP.Parser.Seal (
  parseURISeal
  ) where

import Data.SMTP.Types.Seal
-- import Data.SMTP.Types.Resource
import qualified Data.Attoparsec.Text as A
import qualified Data.ByteString.Base64.URL as B64
import Data.ByteString (ByteString)
import Text.StringConvert

{- |
Parses a seal inside a URI parameter.

In the format: cpId:code[:nonce]

Where all the values are binary octet streams
encoded in base64url.
-}
parseURISeal :: A.Parser Seal
parseURISeal = do
  mycp <- base64
  A.string ":"
  mycode <- base64
  A.choice [
    do
      A.string ":"
      mynonce <- base64
      return . Seal mycp mycode $ Just mynonce,
    return $ Seal mycp mycode Nothing
    ]

base64 :: A.Parser ByteString
base64 = do
  e <- A.takeWhile isBase64Char
  case B64.decode . s $ e of
    Left r -> fail r
    Right r -> return r
  where
    isBase64Char c
      | c >= '0' && c <= '9' = True
      | c >= 'a' && c <= 'z' = True
      | c >= 'A' && c <= 'Z' = True
      | c == '+' || c == '-' || c == '=' = True
      | otherwise = False