module Utils.Lens.TH where

import ClassyPrelude (String, Maybe(..))
import Control.Lens
import Control.Lens.Internal.FieldTH
import Language.Haskell.TH

-- import Control.Lens.Misc
{-
    NOTE: The code for lensRules_  and makeLenses_ was stolen from package lens-misc-0.0.2.0,
    which was currently unavailable in our stack snapshot.
    See https://github.com/louispan/lens-misc
-}

-- | A 'LensRules' used by 'makeLenses_'.
lensRules_ :: LensRules
lensRules_ = lensRules
    & lensField .~ \_ _ n -> [TopName (mkName ('_':nameBase n))]

-- | Like @lensRules_@, but different class and function name
classyRulesFor_ :: ClassyNamer -> LensRules
classyRulesFor_ clsNamer = classyRules
    & lensClass .~ clsNamer
    & lensField .~ \_ _ n -> [TopName (mkName ('_':nameBase n))]


-- | Build lenses (and traversals) with a sensible default configuration.
-- Works the same as 'makeLenses' except that
-- the resulting lens is also prefixed with an underscore.
--
-- /e.g./
--
-- @
-- data FooBar
--   = Foo { x, y :: 'Int' }
--   | Bar { x :: 'Int' }
-- 'makeLenses' ''FooBar
-- @
--
-- will create
--
-- @
-- _x :: 'Lens'' FooBar 'Int'
-- _x f (Foo a b) = (\\a\' -> Foo a\' b) \<$\> f a
-- _x f (Bar a)   = Bar \<$\> f a
-- _y :: 'Traversal'' FooBar 'Int'
-- _y f (Foo a b) = (\\b\' -> Foo a  b\') \<$\> f b
-- _y _ c\@(Bar _) = pure c
-- @
--
-- @
-- 'makeLenses_' = 'makeLensesWith' 'lensRules_'
-- @
makeLenses_ :: Name -> DecsQ
makeLenses_ = makeFieldOptics lensRules_

-- | like makeClassyFor but only specifies names for class and its function,
--   otherwise lenses are created with underscore like `makeLenses_`
makeClassyFor_ :: String -> String -> Name -> DecsQ
makeClassyFor_ clsName funName = makeFieldOptics (classyRulesFor_ clNamer)
    where
        clNamer :: ClassyNamer
        -- clNamer _ = Just (clsName, funName) -- for newer versions >= 4.17
        clNamer _ = Just (mkName clsName, mkName funName)