{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE OverloadedStrings #-}
-- |
-- Module       : Data.ByteString.Base64
-- 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 encoding including
-- unpadded and lenient variants
--
module Data.ByteString.Base64
( encodeBase64
, encodeBase64'
, decodeBase64
, encodeBase64Unpadded
, encodeBase64Unpadded'
, decodeBase64Unpadded
, decodeBase64Lenient
, isBase64
, isValidBase64
) where


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


-- | Encode a 'ByteString' value as Base64 'Text' with padding.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-4 RFC-4648 section 4>
--
encodeBase64 :: ByteString -> Text
encodeBase64 = T.decodeUtf8 . encodeBase64'
{-# INLINE encodeBase64 #-}

-- | Encode a 'ByteString' value as a Base64 'ByteString'  value with padding.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-4 RFC-4648 section 4>
--
encodeBase64' :: ByteString -> ByteString
encodeBase64' = encodeBase64_ base64Table
{-# INLINE encodeBase64' #-}

-- | Decode a padded Base64-encoded 'ByteString' value.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-4 RFC-4648 section 4>
--
decodeBase64 :: ByteString -> Either Text ByteString
decodeBase64 = decodeBase64_ False decodeB64Table
{-# INLINE decodeBase64 #-}

-- | Encode a 'ByteString' value as Base64 'Text' without padding.
--
-- __Note:__ in some circumstances, the use of padding ("=") in base-encoded data
-- is not required or used. This is not one of them. If you are absolutely sure
-- the length of your bytestring is divisible by 3, this function will be the same
-- as 'encodeBase64' with padding, however, if not, you may see garbage appended to
-- your bytestring.
--
-- Only call unpadded variants when you can make assumptions about the length of
-- your input data.
--
-- 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 Base64 without padding.
--
-- __Note:__ in some circumstances, the use of padding ("=") in base-encoded data
-- is not required or used. This is not one of them. If you are absolutely sure
-- the length of your bytestring is divisible by 3, this function will be the same
-- as 'encodeBase64' with padding, however, if not, you may see garbage appended to
-- your bytestring.
--
-- Only call unpadded variants when you can make assumptions about the length of
-- your input data.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-3.2 RFC-4648 section 3.2>
--
encodeBase64Unpadded' :: ByteString -> ByteString
encodeBase64Unpadded' =  BS.takeWhile ((/=) 0x3d) . encodeBase64_ base64Table
{-# INLINE encodeBase64Unpadded' #-}

-- | Decode an unpadded Base64-encoded 'ByteString'.
--
-- __Note:__ Only call unpadded variants when you can make assumptions
-- about the length of your input data.
--
-- See: <https://tools.ietf.org/html/rfc4648#section-3.2 RFC-4648 section 3.2>
--
decodeBase64Unpadded :: ByteString -> Either Text ByteString
decodeBase64Unpadded = decodeBase64_ False decodeB64Table
{-# INLINE decodeBase64Unpadded #-}

-- | Leniently decode an unpadded Base64-encoded 'ByteString' value. 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_ decodeB64Table
{-# INLINE decodeBase64Lenient #-}

-- | Tell whether a 'ByteString' value is base64 encoded.
--
isBase64 :: ByteString -> Bool
isBase64 bs = isValidBase64 bs && isRight (decodeBase64 bs)
{-# INLINE isBase64 #-}

-- | Tell whether a 'ByteString' value is a valid Base64 format.
--
-- This will not tell you whether or not this is a correct Base64url representation,
-- only that it conforms to the correct shape. To check whether it is a true
-- Base64 encoded 'ByteString' value, use 'isBase64'.
--
isValidBase64 :: ByteString -> Bool
isValidBase64 = validateBase64 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
{-# INLINE isValidBase64 #-}