{-# LANGUAGE OverloadedStrings #-}
-- |
-- Module       : Data.ByteString.Base64.URL
-- Copyright 	: (c) 2019 Emily Pillmore
-- License	: BSD-style
--
-- Maintainer	: Emily Pillmore <emilypi@cohomolo.gy>
-- Stability	: Experimental
-- Portability	: portable
--
-- This module contains the combinators implementing the
-- RFC 4648 specification for the Base64-URL encoding including
-- unpadded and lenient variants
--
module Data.ByteString.Base64.URL
( encodeBase64
, encodeBase64'
, decodeBase64
, encodeBase64Unpadded
, encodeBase64Unpadded'
, decodeBase64Unpadded
, decodeBase64Lenient
, isBase64Url
) where

import Data.ByteString (ByteString)
import qualified Data.ByteString as BS
import Data.ByteString.Base64.Internal
import Data.Text (Text)
import qualified Data.Text.Encoding as T


-- | Encode a 'ByteString' value as a Base64url 'Text' value with padding.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-5 RFC-4648 section 5>
--
encodeBase64 :: ByteString -> Text
encodeBase64 = T.decodeUtf8 . encodeBase64'
{-# INLINE encodeBase64 #-}

-- | Encode a 'ByteString' as a Base64url 'ByteString' value with padding.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-5 RFC-4648 section 5>
--
encodeBase64' :: ByteString -> ByteString
encodeBase64' = encodeBase64_ base64UrlTable
{-# INLINE encodeBase64' #-}

-- | Decode a padded Base64url encoded 'ByteString' value. If its length is not a multiple
-- of 4, then padding chars will be added to fill out the input to a multiple of
-- 4 for safe decoding as Base64url-encoded values are optionally padded.
--
-- For a decoder that fails on unpadded input of incorrect size, use 'decodeBase64Unpadded'.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-4 RFC-4648 section 4>
--
decodeBase64 :: ByteString -> Either Text ByteString
decodeBase64 = decodeBase64_ True decodeB64UrlTable
{-# INLINE decodeBase64 #-}

-- | Encode a 'ByteString' value as Base64url 'Text' without padding. Note that for Base64url,
-- padding is optional. If you call this function, you will simply be encoding
-- as Base64url and stripping padding chars from the output.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-3.2 RFC-4648 section 3.2>
--
encodeBase64Unpadded :: ByteString -> Text
encodeBase64Unpadded = T.decodeUtf8 . encodeBase64Unpadded'
{-# INLINE encodeBase64Unpadded #-}

-- | Encode a 'ByteString' value as Base64url without padding. Note that for Base64url,
-- padding is optional. If you call this function, you will simply be encoding
-- as Base64url and stripping padding chars from the output.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-3.2 RFC-4648 section 3.2>
--
encodeBase64Unpadded' :: ByteString -> ByteString
encodeBase64Unpadded' = BS.takeWhile ((/=) 0x3d) . encodeBase64_ base64UrlTable
{-# INLINE encodeBase64Unpadded' #-}

-- | Decode a padded Base64url-encoded 'ByteString' value. If its length is not a multiple
-- of 4, then padding chars will /not/ be added to fill out the input to a multiple of
-- 4.
--
-- In general, unless unpadded Base64url is explicitly required, it is
-- safer to call 'decodeBase64'.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-4 RFC-4648 section 4>
--
decodeBase64Unpadded :: ByteString -> Either Text ByteString
decodeBase64Unpadded = decodeBase64_ False decodeB64UrlTable
{-# INLINE decodeBase64Unpadded #-}

-- | Leniently decode an unpadded Base64url-encoded 'ByteString'. This function
-- will not generate parse errors. If input data contains padding chars,
-- then the input will be parsed up until the first pad character.
--
-- __Note:__ This is not RFC 4648-compliant.
--
decodeBase64Lenient :: ByteString -> ByteString
decodeBase64Lenient = decodeBase64Lenient_ decodeB64UrlTable
{-# INLINE decodeBase64Lenient #-}

-- | Tell whether a bytestring is Base64-encoded
--
isBase64Url :: ByteString -> Bool
isBase64Url = BS.all (`BS.elem` alphabet)
  where
    alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
{-# INLINE isBase64Url #-}