{-# OPTIONS --safe --without-K #-}
 
module Class.MonadReader where
 
open import Meta.Prelude
 
open import Class.Core
open import Class.Functor
open import Class.Applicative
open import Class.Monad
open import Class.MonadError
 
open MonadError ⦃...⦄
 
record MonadReader (R : Set ℓ) (M : Type↑) ⦃ _ : Monad M ⦄ : Setω where
  field
    ask : M R
    local : ∀ {a} {A : Set a} → (R → R) → M A → M A
 
  reader : ∀ {a} {A : Set a} → (R → A) → M A
  reader f = f <$> ask
 
open MonadReader ⦃...⦄
 
ReaderT : (R : Set) (M : ∀ {a} → Set a → Set a) → ∀ {a} → Set a → Set a
ReaderT R M A = R → M A
 
module _ {R : Set} {M : ∀ {a} → Set a → Set a} where
 
  Functor-ReaderT : ⦃ Functor M ⦄ → Functor (ReaderT R M)
  Functor-ReaderT ._<$>_ f ra r = f <$> ra r
 
  instance _ = Functor-ReaderT
 
  Applicative-ReaderT : ⦃ Applicative M ⦄ → Applicative (ReaderT R M)
  Applicative-ReaderT .pure a = const (pure a)
  Applicative-ReaderT ._<*>_ rf ra r = rf r <*> ra r
 
  instance _ = Applicative-ReaderT
 
  Monad-ReaderT : ⦃ Monad M ⦄ → Monad (ReaderT R M)
  Monad-ReaderT .return a _ = return a
  Monad-ReaderT ._>>=_ x f r = x r >>= flip f r
 
  instance _ = Monad-ReaderT
 
  MonadReader-ReaderT : ⦃ _ : Monad M ⦄ → MonadReader R (ReaderT R M)
  MonadReader-ReaderT .ask r = return r
  MonadReader-ReaderT .local f x = x ∘ f
 
  MonadError-ReaderT : ∀ {e} {E : Set e} → ⦃ MonadError E M ⦄ → MonadError E (ReaderT R M)
  MonadError-ReaderT .error e _ = error e
  MonadError-ReaderT .catch x h r = catch (x r) (flip h r)