module Main where

import Prelude (Unit)
import Effect (Effect)
import Effect.Console (log)
import Record.Unsafe (unsafeGet)
import Type.Data.Symbol (class IsSymbol, SProxy, reflectSymbol)
import Type.Row (class Cons) as Row

newtype LBox row a = LBox (∀ r. (∀ lbl _1. Row.Cons lbl a _1 row ⇒ IsSymbol lbl ⇒ SProxy lbl → r) → r)

unLBox ∷ ∀ row a r. (∀ lbl _1. Row.Cons lbl a _1 row ⇒ IsSymbol lbl ⇒ SProxy lbl → r) → LBox row a → r
unLBox g (LBox f) = f g

-- Example 1
lboxIdentity ∷ ∀ row a. LBox row a → LBox row a
lboxIdentity = unLBox \lbl → LBox \f → f lbl

-- Example 2
read ∷ ∀ row a. Record row → LBox row a → a
read rec = unLBox \lbl → get lbl rec

get
  :: forall r r' l a
   . IsSymbol l
  => Row.Cons l a r' r
  => SProxy l
  -> Record r
  -> a
get l r = unsafeGet (reflectSymbol l) r

main :: Effect Unit
main = log "Done"