typed-encoding

Type level annotations, string transformations, and other goodies that make programming strings safer.

Motivation

I have recently spent a lot of time troubleshooting various Base64, quoted-printable, and UTF-8 encoding issues.
I decided to write a library that will help avoiding issues like these.

This library allows to specify and work with types like

-- some data encoded in base 64
mydata :: Enc '["enc-B64"] ByteString

-- some text (utf8) data encoded in base 64 
myData :: Enc '["enc-B64", "r-UTF8"] ByteString

It allows to define precise string content annotations like:

mydata :: Enc '["r-IpV4"] Text

and provides ways for

• encoding
• decoding
• recreation (encoding validation)
• type conversions
• converting types to encoded strings
• typesafe conversion of encoded strings to types

... but this approach seems to be a bit more...

-- upper cased text encoded as base64
example :: Enc '["enc-B64", "do-UPPER"] () T.Text
example = encodeAll . toEncoding () $ "some text goes here"

It becomes a type directed, declarative approach to string transformations.

Transformations can be

• used with parameters.
• applied or undone partially (if encoding is reversible)

Examples

Please see Examples.TypedEncoding it the module list.

Dependencies on other encoding libs

Currently it uses

• base64-bytestring because it was my driving example
• I will try to separate other deps like servant, specific encoding libraries, etc into separate libs if there is interest. I consider orphan instances to be OK in this context. (GHC will classify them as such despite use of unique symbols.)

Plans, some TODOs

• lensifying conversions
• better implementation type safety

Tested with

• stack (1.9.3) lts-14.27 (ghc-8.6.5)

Known issues

• running test suite: cabal has problems with doctest, use stack
  https://github.com/haskell/cabal/issues/6087