{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE UndecidableInstances #-}
{-# OPTIONS_GHC -Wno-orphans #-}

module Worksheets.Utils.Generics (
  module Worksheets.Utils.Generics,
  module GHC.Generics,
) where

import Data.Char qualified as Char
import GHC.Generics
import Prelude (Eq (..), Maybe (..), String, otherwise, (<>))

-- | Cut the first lowercases, and lowercase the first uppercase.
dropLowercasesAndLowerNextChar :: String -> String
dropLowercasesAndLowerNextChar "" = ""
dropLowercasesAndLowerNextChar (c : cs)
  | Char.isUpper c = Char.toLower c : cs
  | otherwise = dropLowercasesAndLowerNextChar cs

-- | Cut the first lowercases, and lowercase the first uppercase.
dropUntilUnderscore :: String -> String
dropUntilUnderscore "" = ""
dropUntilUnderscore (c : cs)
  | c == '_' = cs
  | otherwise = dropUntilUnderscore cs

class DataSelectorNames f where
  -- | List the names of the selectors of a data type.
  dataSelectorNames :: [String]
instance DataSelectorNames (Rep a ()) => DataSelectorNames (Generically a) where
  dataSelectorNames = dataSelectorNames @(Rep a ())

{-
instance (DataSelectorNames f) => DataSelectorNames (M1 D t f) where
  dataSelectorNames = dataSelectorNames @f
instance (DataSelectorNames f, DataSelectorNames g) => DataSelectorNames (f :+: g) where
  dataSelectorNames = dataSelectorNames @f <> dataSelectorNames @g
instance DataSelectorNames (C1 c f) where
  dataSelectorNames = [conName (undefined :: C1 c f g)]
-}

deriving instance DataSelectorNames c => DataSelectorNames (K1 i c p)
deriving instance DataSelectorNames p => DataSelectorNames (Par1 p)
deriving instance DataSelectorNames (f p) => DataSelectorNames (Rec1 f p)

-- instance DataSelectorNames (f p) => DataSelectorNames (M1 i c f p) where dataSelectorNames = dataSelectorNames @(f p)
instance (DataSelectorNames (f p), DataSelectorNames (g p)) => DataSelectorNames ((f :*: g) p) where
  dataSelectorNames = dataSelectorNames @(f p) <> dataSelectorNames @(g p)
deriving instance DataSelectorNames (f (g p)) => DataSelectorNames ((f :.: g) p)
instance
  DataSelectorNames (f p) =>
  DataSelectorNames (M1 D (MetaData typeName moduleName packageName isNewtype) f p)
  where
  dataSelectorNames = dataSelectorNames @(f p)
instance
  DataSelectorNames (f p) =>
  DataSelectorNames (M1 C (MetaCons consName consFixity consHasRecordSelectors) f p)
  where
  dataSelectorNames = dataSelectorNames @(f p)
instance
  Selector (MetaSel (Just selName) selUnpackedness selStrictness selStrictnessInferred) =>
  DataSelectorNames (M1 S (MetaSel (Just selName) selUnpackedness selStrictness selStrictnessInferred) f p)
  where
  dataSelectorNames = [selName n]
    where
      n :: M1 S (MetaSel (Just selName) selUnpackedness selStrictness selStrictnessInferred) f p
      n = n