{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE NoImplicitPrelude #-}

module Data.Morpheus.NamedResolvers
  ( ResolveNamed (..),
    NamedResolverT (..),
    resolve,
  )
where

import Data.Aeson (ToJSON)
import Data.Morpheus.Types.ID (ID)
import Relude

instance Monad m => ResolveNamed m ID where
  type Dep ID = ID
  resolveNamed :: Monad m => Dep ID -> m ID
resolveNamed = forall (f :: * -> *) a. Applicative f => a -> f a
pure

instance Monad m => ResolveNamed m Text where
  type Dep Text = Text
  resolveNamed :: Monad m => Dep Text -> m Text
resolveNamed = forall (f :: * -> *) a. Applicative f => a -> f a
pure

class (ToJSON (Dep a)) => ResolveNamed (m :: Type -> Type) a where
  type Dep a :: Type
  resolveNamed :: Monad m => Dep a -> m a

instance (ResolveNamed m a) => ResolveNamed (m :: Type -> Type) (Maybe a) where
  type Dep (Maybe a) = Maybe (Dep a)
  resolveNamed :: Monad m => Dep (Maybe a) -> m (Maybe a)
resolveNamed (Just Dep a
x) = forall a. a -> Maybe a
Just forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> forall (m :: * -> *) a. (ResolveNamed m a, Monad m) => Dep a -> m a
resolveNamed Dep a
x
  resolveNamed Maybe (Dep a)
Dep (Maybe a)
Nothing = forall (f :: * -> *) a. Applicative f => a -> f a
pure forall a. Maybe a
Nothing

instance (ResolveNamed m a) => ResolveNamed (m :: Type -> Type) [a] where
  type Dep [a] = [Dep a]
  resolveNamed :: Monad m => Dep [a] -> m [a]
resolveNamed = forall (t :: * -> *) (f :: * -> *) a b.
(Traversable t, Applicative f) =>
(a -> f b) -> t a -> f (t b)
traverse forall (m :: * -> *) a. (ResolveNamed m a, Monad m) => Dep a -> m a
resolveNamed

data NamedResolverT (m :: Type -> Type) a where
  Ref :: ResolveNamed m a => m (Dep a) -> NamedResolverT m a
  Refs :: ResolveNamed m a => m [Dep a] -> NamedResolverT m [a]
  Value :: m a -> NamedResolverT m a

-- RESOLVER TYPES
data RES = VALUE | LIST | REF

type family RES_TYPE a b :: RES where
  RES_TYPE a a = 'VALUE
  RES_TYPE [a] [b] = 'LIST
  RES_TYPE a b = 'REF

resolve :: forall m a b. (ResolveByType (RES_TYPE a b) m a b) => Monad m => m a -> NamedResolverT m b
resolve :: forall (m :: * -> *) a b.
(ResolveByType (RES_TYPE a b) m a b, Monad m) =>
m a -> NamedResolverT m b
resolve = forall (k :: RES) (m :: * -> *) a b (f :: RES -> *).
(ResolveByType k m a b, Monad m) =>
f k -> m a -> NamedResolverT m b
resolveByType (forall {k} (t :: k). Proxy t
Proxy :: Proxy (RES_TYPE a b))

class Dep b ~ a => ResolveByType (k :: RES) m a b where
  resolveByType :: Monad m => f k -> m a -> NamedResolverT m b

instance (ResolveNamed m a, Dep a ~ a) => ResolveByType 'VALUE m a a where
  resolveByType :: forall (f :: RES -> *).
Monad m =>
f 'VALUE -> m a -> NamedResolverT m a
resolveByType f 'VALUE
_ = forall (m :: * -> *) a. m a -> NamedResolverT m a
Value

instance (ResolveNamed m b, Dep b ~ a) => ResolveByType 'LIST m [a] [b] where
  resolveByType :: forall (f :: RES -> *).
Monad m =>
f 'LIST -> m [a] -> NamedResolverT m [b]
resolveByType f 'LIST
_ = forall (m :: * -> *) a.
ResolveNamed m a =>
m [Dep a] -> NamedResolverT m [a]
Refs

instance (ResolveNamed m b, Dep b ~ a) => ResolveByType 'REF m a b where
  resolveByType :: forall (f :: RES -> *).
Monad m =>
f 'REF -> m a -> NamedResolverT m b
resolveByType f 'REF
_ = forall (m :: * -> *) a.
ResolveNamed m a =>
m (Dep a) -> NamedResolverT m a
Ref