jwk.hs

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE DeriveFoldable #-}

import Control.Lens

import Data.Foldable

newtype JWKSet = JWKSet [JWK]

data JWK = JWK
  deriving Show

class JWKStore a where
  keys :: Fold a JWK

instance Foldable t => JWKStore (t JWK) where
  keys = folding id

instance JWKStore JWKSet where
  keys = folding (\(JWKSet xs) -> xs)

data ContrivedJWKThingo a = ContrivedJWKThingo [JWK] [a] deriving Foldable

instance JWKStore (ContrivedJWKThingo a) where
  keys = folding (\(ContrivedJWKThingo js _) -> js)

v :: ContrivedJWKThingo JWK
v = ContrivedJWKThingo [JWK, JWK] [JWK, JWK, JWK]

-- what code goes here to screw up?

----

class GetKeys a where
  getKeys :: a -> [Char]

instance Foldable t => GetKeys (t Char) where
  getKeys = toList

data HasInts a = HasInts [Char] [a] deriving Foldable

instance GetKeys (HasInts a) where
  getKeys (HasInts is _) = is

e :: HasInts Char
e = HasInts ['a', 'b', 'c'] ['d', 'e', 'f']

r = getKeys (HasInts ['a', 'b', 'c'] ['d', 'e', 'f'])