{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}

module DataFrame.Internal.Schema where

import qualified Data.Map as M
import qualified Data.Proxy as P
import qualified Data.Text as T

import Data.Maybe
import Data.Type.Equality (TestEquality (..), type (:~:) (Refl))
import DataFrame.Internal.Column
import Type.Reflection (typeRep)

data SchemaType where
    SType :: (Columnable a) => P.Proxy a -> SchemaType

instance Show SchemaType where
    show (SType (_ :: P.Proxy a)) = show (typeRep @a)

instance Eq SchemaType where
    (==) (SType (_ :: P.Proxy a)) (SType (_ :: P.Proxy b)) = isJust (testEquality (typeRep @a) (typeRep @b))

schemaType :: forall a. (Columnable a) => SchemaType
schemaType = SType (P.Proxy @a)

data Schema = Schema
    { elements :: M.Map T.Text SchemaType
    }
    deriving (Show, Eq)