{-# LANGUAGE GADTs #-}

module Lib where

import Data.Map.Strict

data Value
    = ValueBool Bool
    | ValueText String

data Expr t where
    ExprBool :: Bool -> Expr Bool
    ExprBoolOr :: Expr Bool -> Expr Bool -> Expr Bool
    ExprText :: String -> Expr String
    ExprTextAppend :: Expr String -> Expr String -> Expr String
    ExprObject :: Map String Value -> String -> Expr Value

eval :: Expr t -> t
eval (ExprBool value) = value
eval (ExprBoolOr (ExprBool lft) (ExprBool rgt)) = lft || rgt
eval (ExprText value) = value
eval (ExprTextAppend (ExprText lft) (ExprText rgt)) = lft <> rgt
eval (ExprObject map fieldName)
    = case map ! fieldName of
        ValueBool boolValue -> ???
        ValueText textValue -> ???