{-# LANGUAGE CPP #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE AllowAmbiguousTypes    #-}
{-# LANGUAGE DataKinds              #-}
{-# LANGUAGE FlexibleContexts       #-}
{-# LANGUAGE FlexibleInstances      #-}
{-# LANGUAGE KindSignatures         #-}
{-# LANGUAGE MultiParamTypeClasses  #-}
{-# LANGUAGE ScopedTypeVariables    #-}
{-# LANGUAGE TypeFamilies           #-}
{-# LANGUAGE TypeOperators          #-}
{-# LANGUAGE UndecidableInstances   #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Generics.Sum.Typed
-- Copyright   :  (C) 2019 Csongor Kiss
-- License     :  BSD3
-- Maintainer  :  Csongor Kiss <kiss.csongor.kiss@gmail.com>
-- Stability   :  experimental
-- Portability :  non-portable
--
-- Derive constructor-field-type-based prisms generically.
--
-----------------------------------------------------------------------------

module Data.Generics.Sum.Typed
  ( -- *Prisms
    --
    --  $setup
    AsType (..)
  ) where

import Data.Kind
import GHC.Generics
import GHC.TypeLits (TypeError, ErrorMessage (..), Symbol)
import Data.Generics.Sum.Internal.Typed
import Data.Generics.Internal.Errors

import Data.Generics.Internal.Families
import Data.Generics.Internal.Void
import Data.Generics.Product.Internal.HList
import Data.Generics.Internal.VL.Prism
import Data.Generics.Internal.Profunctor.Iso
import Data.Generics.Internal.Profunctor.Prism (prismPRavel)

-- $setup
-- >>> :set -XTypeApplications
-- >>> :set -XDataKinds
-- >>> :set -XDeriveGeneric
-- >>> import GHC.Generics
-- >>> :m +Data.Generics.Internal.VL.Prism
-- >>> :{
-- data Animal
--   = Dog Dog
--   | Cat Name Age
--   | Duck Age
--   | Turtle Age
--   deriving (Generic, Show)
-- data Dog
--   = MkDog
--   { name :: Name
--   , age  :: Age
--   }
--   deriving (Generic, Show)
-- type Name = String
-- newtype Age  = Age Int deriving Show
-- dog, cat, duck :: Animal
-- dog = Dog (MkDog "Shep" (Age 3))
-- cat = Cat "Mog" (Age 5)
-- duck = Duck (Age 2)
-- :}


-- |Sums that have a constructor with a field of the given type.
class AsType a s where
  -- |A prism that projects a constructor uniquely identifiable by the type of
  --  its field. Compatible with the lens package's 'Control.Lens.Prism' type.
  --
  --  >>> dog ^? _Typed @Dog
  --  Just (MkDog {name = "Shep", age = Age 3})
  --  >>> cat ^? _Typed @(Name, Age)
  --  Just ("Mog",Age 5)
  --  >>> dog ^? _Typed @Age
  --  ...
  --  ...
  --  ... The type Animal contains multiple constructors whose fields are of type Age.
  --  ... The choice of constructor is thus ambiguous, could be any of:
  --  ... Duck
  --  ... Turtle
  --  ...
  _Typed :: Prism' s a
  _Typed = (a -> s) -> (s -> Either s a) -> Prism s s a a
forall b t s a. (b -> t) -> (s -> Either t a) -> Prism s t a b
prism a -> s
forall a s. AsType a s => a -> s
injectTyped (\i :: s
i -> Either s a -> (a -> Either s a) -> Maybe a -> Either s a
forall b a. b -> (a -> b) -> Maybe a -> b
maybe (s -> Either s a
forall a b. a -> Either a b
Left s
i) a -> Either s a
forall a b. b -> Either a b
Right (s -> Maybe a
forall a s. AsType a s => s -> Maybe a
projectTyped s
i))
  {-# INLINE[2] _Typed #-}

  -- |Inject by type.
  injectTyped :: a -> s
  injectTyped
    = (Tagged a (Identity a) -> Tagged s (Identity s)) -> a -> s
forall b t.
(Tagged b (Identity b) -> Tagged t (Identity t)) -> b -> t
build Tagged a (Identity a) -> Tagged s (Identity s)
forall a s. AsType a s => Prism s s a a
_Typed

  -- |Project by type.
  projectTyped :: s -> Maybe a
  projectTyped
    = (s -> Maybe a) -> (a -> Maybe a) -> Either s a -> Maybe a
forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
either (Maybe a -> s -> Maybe a
forall a b. a -> b -> a
const Maybe a
forall a. Maybe a
Nothing) a -> Maybe a
forall a. a -> Maybe a
Just (Either s a -> Maybe a) -> (s -> Either s a) -> s -> Maybe a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Prism s s a a -> s -> Either s a
forall s t a b. Prism s t a b -> s -> Either t a
match forall a s. AsType a s => Prism s s a a
Prism s s a a
_Typed

  {-# MINIMAL (injectTyped, projectTyped) | _Typed #-}

instance
  ( Generic s
  , ErrorUnlessOne a s (CollectPartialType as (Rep s))
  , as ~ TupleToList a
  , ListTuple a as
  , GAsType (Rep s) as
  , Defined (Rep s)
    (NoGeneric s '[ 'Text "arising from a generic prism focusing on a constructor of type " ':<>: QuoteType a])
    (() :: Constraint)
  ) => AsType a s where

  _Typed :: p a (f a) -> p s (f s)
_Typed eta :: p a (f a)
eta = (Market a a a a -> Market a a s s) -> p a (f a) -> p s (f s)
forall a b s t. (Market a b a b -> Market a b s t) -> Prism s t a b
prismRavel ((Market a a a a -> Market a a s s) -> Prism s s a a
forall s t a b. APrism s t a b -> Prism s t a b
prismPRavel (Market a a (Rep s Any) (Rep s Any) -> Market a a s s
forall a b x. (Generic a, Generic b) => Iso a b (Rep a x) (Rep b x)
repIso (Market a a (Rep s Any) (Rep s Any) -> Market a a s s)
-> (Market a a a a -> Market a a (Rep s Any) (Rep s Any))
-> Market a a a a
-> Market a a s s
forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall x.
GAsType (Rep s) as =>
Prism (Rep s x) (Rep s x) (HList as) (HList as)
forall (f :: * -> *) (as :: [*]) x.
GAsType f as =>
Prism (f x) (f x) (HList as) (HList as)
_GTyped @_ @as (Market a a (HList as) (HList as)
 -> Market a a (Rep s Any) (Rep s Any))
-> (Market a a a a -> Market a a (HList as) (HList as))
-> Market a a a a
-> Market a a (Rep s Any) (Rep s Any)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Market a a a a -> Market a a (HList as) (HList as)
forall tuple (as :: [*]).
ListTuple tuple as =>
Iso' (HList as) tuple
tupled)) p a (f a)
eta
  {-# INLINE[2] _Typed #-}

-- | See Note [Uncluttering type signatures]
#if __GLASGOW_HASKELL__ < 804
-- >>> :t _Typed
-- _Typed
--   :: (Applicative f, Data.Profunctor.Choice.Choice p, AsType a s) =>
--      p a (f a) -> p s (f s)
#else
-- >>> :t _Typed
-- _Typed
--   :: (AsType a s, Data.Profunctor.Choice.Choice p, Applicative f) =>
--      p a (f a) -> p s (f s)
#endif
instance {-# OVERLAPPING #-} AsType a Void where
  _Typed :: p a (f a) -> p Void (f Void)
_Typed = p a (f a) -> p Void (f Void)
forall a. HasCallStack => a
undefined
  injectTyped :: a -> Void
injectTyped = a -> Void
forall a. HasCallStack => a
undefined
  projectTyped :: Void -> Maybe a
projectTyped = Void -> Maybe a
forall a. HasCallStack => a
undefined

-- | See Note [Uncluttering type signatures]
#if __GLASGOW_HASKELL__ < 804
-- >>> :t _Typed @Int
-- _Typed @Int
--   :: (Applicative f, Data.Profunctor.Choice.Choice p,
--       AsType Int s) =>
--      p Int (f Int) -> p s (f s)
#else
-- >>> :t _Typed @Int
-- _Typed @Int
--   :: (AsType Int s, Data.Profunctor.Choice.Choice p,
--       Applicative f) =>
--      p Int (f Int) -> p s (f s)
#endif
instance {-# OVERLAPPING #-} AsType Void a where
  _Typed :: p Void (f Void) -> p a (f a)
_Typed = p Void (f Void) -> p a (f a)
forall a. HasCallStack => a
undefined
  injectTyped :: Void -> a
injectTyped = Void -> a
forall a. HasCallStack => a
undefined
  projectTyped :: a -> Maybe Void
projectTyped = a -> Maybe Void
forall a. HasCallStack => a
undefined

type family ErrorUnlessOne (a :: Type) (s :: Type) (ctors :: [Symbol]) :: Constraint where
  ErrorUnlessOne _ _ '[_]
    = ()

  ErrorUnlessOne a s '[]
    = TypeError
        (     'Text "The type "
        ':<>: 'ShowType s
        ':<>: 'Text " does not contain a constructor whose field is of type "
        ':<>: 'ShowType a
        )

  ErrorUnlessOne a s cs
    = TypeError
        (     'Text "The type "
        ':<>: 'ShowType s
        ':<>: 'Text " contains multiple constructors whose fields are of type "
        ':<>: 'ShowType a ':<>: 'Text "."
        ':$$: 'Text "The choice of constructor is thus ambiguous, could be any of:"
        ':$$: ShowSymbols cs
        )