{-|
Module      : Toml.ToValue.Matcher
Description : GHC.Generics derived table generation
Copyright   : (c) Eric Mertens, 2023
License     : ISC
Maintainer  : emertens@gmail.com

Use 'genericToTable' to derive an instance of 'Toml.ToValue.ToTable'
using the field names of a record.

-}
module Toml.ToValue.Generic (
    GToTable(..),
    genericToTable,
    ) where

import Data.Map qualified as Map
import GHC.Generics
import Toml.Value (Table)
import Toml.ToValue (ToValue(..))

-- | Use a record's field names to generate a 'Table'
--
-- @since 1.0.2.0
genericToTable :: (Generic a, GToTable (Rep a)) => a -> Table
genericToTable :: forall a. (Generic a, GToTable (Rep a)) => a -> Table
genericToTable = Rep a Any -> Table
forall a. Rep a a -> Table
forall (f :: * -> *) a. GToTable f => f a -> Table
gToTable (Rep a Any -> Table) -> (a -> Rep a Any) -> a -> Table
forall b c a. (b -> c) -> (a -> b) -> a -> c
. a -> Rep a Any
forall x. a -> Rep a x
forall a x. Generic a => a -> Rep a x
from
{-# INLINE genericToTable #-}

-- | Supports conversion of product types with field selector names
-- to TOML values.
--
-- @since 1.0.2.0
class GToTable f where
    gToTable :: f a -> Table

-- | Ignores type constructor names
instance GToTable f => GToTable (D1 c f) where
    gToTable :: forall a. D1 c f a -> Table
gToTable (M1 f a
x) = f a -> Table
forall a. f a -> Table
forall (f :: * -> *) a. GToTable f => f a -> Table
gToTable f a
x
    {-# INLINE gToTable #-}

-- | Ignores value constructor names
instance GToTable f => GToTable (C1 c f) where
    gToTable :: forall a. C1 c f a -> Table
gToTable (M1 f a
x) = f a -> Table
forall a. f a -> Table
forall (f :: * -> *) a. GToTable f => f a -> Table
gToTable f a
x
    {-# INLINE gToTable #-}

instance (GToTable f, GToTable g) => GToTable (f :*: g) where
    gToTable :: forall a. (:*:) f g a -> Table
gToTable (f a
x :*: g a
y) = f a -> Table
forall a. f a -> Table
forall (f :: * -> *) a. GToTable f => f a -> Table
gToTable f a
x Table -> Table -> Table
forall a. Semigroup a => a -> a -> a
<> g a -> Table
forall a. g a -> Table
forall (f :: * -> *) a. GToTable f => f a -> Table
gToTable g a
y
    {-# INLINE gToTable #-}

-- | Omits the key from the table on nothing, includes it on just
instance {-# OVERLAPS #-} (Selector s, ToValue a) => GToTable (S1 s (K1 i (Maybe a))) where
    gToTable :: forall a. S1 s (K1 i (Maybe a)) a -> Table
gToTable (M1 (K1 Maybe a
Nothing)) = Table
forall k a. Map k a
Map.empty
    gToTable s :: M1 S s (K1 i (Maybe a)) a
s@(M1 (K1 (Just a
x))) = [Char] -> Value -> Table
forall k a. k -> a -> Map k a
Map.singleton (M1 S s (K1 i (Maybe a)) a -> [Char]
forall {k} (s :: k) k1 (t :: k -> (k1 -> *) -> k1 -> *)
       (f :: k1 -> *) (a :: k1).
Selector s =>
t s f a -> [Char]
forall k1 (t :: Meta -> (k1 -> *) -> k1 -> *) (f :: k1 -> *)
       (a :: k1).
t s f a -> [Char]
selName M1 S s (K1 i (Maybe a)) a
s) (a -> Value
forall a. ToValue a => a -> Value
toValue a
x)
    {-# INLINE gToTable #-}

-- | Uses record selector name as table key
instance (Selector s, ToValue a) => GToTable (S1 s (K1 i a)) where
    gToTable :: forall a. S1 s (K1 i a) a -> Table
gToTable s :: S1 s (K1 i a) a
s@(M1 (K1 a
x)) = [Char] -> Value -> Table
forall k a. k -> a -> Map k a
Map.singleton (S1 s (K1 i a) a -> [Char]
forall {k} (s :: k) k1 (t :: k -> (k1 -> *) -> k1 -> *)
       (f :: k1 -> *) (a :: k1).
Selector s =>
t s f a -> [Char]
forall k1 (t :: Meta -> (k1 -> *) -> k1 -> *) (f :: k1 -> *)
       (a :: k1).
t s f a -> [Char]
selName S1 s (K1 i a) a
s) (a -> Value
forall a. ToValue a => a -> Value
toValue a
x)
    {-# INLINE gToTable #-}

-- | Emits empty table
instance GToTable U1 where
    gToTable :: forall a. U1 a -> Table
gToTable U1 a
_ = Table
forall k a. Map k a
Map.empty
    {-# INLINE gToTable #-}

instance GToTable V1 where
    gToTable :: forall a. V1 a -> Table
gToTable V1 a
v = case V1 a
v of {}
    {-# INLINE gToTable #-}