Types.hs

{-# LANGUAGE UndecidableInstances #-}

module Web.Hyperbole.HyperView.Types where

import Data.Kind (Type)
import Effectful
import Effectful.Reader.Dynamic
import GHC.Generics
import Web.Hyperbole.Effect.Hyperbole (Hyperbole)
import Web.Hyperbole.HyperView.ViewAction
import Web.Hyperbole.HyperView.ViewId
import Web.Hyperbole.View (View, none)


{- | HyperViews are interactive subsections of a 'Page'

Create an instance with a unique view id type and a sum type describing the actions the HyperView supports. The View Id can contain context (a database id, for example)

@
#EMBED Example/Docs/Interactive.hs data Message

#EMBED Example/Docs/Interactive.hs instance HyperView Message es where
@
-}
class (ViewId id, ViewAction (Action id)) => HyperView id es where
  -- | Outline all actions that are permitted in this HyperView
  --
  -- > data Action Message = SetMessage Text | ClearMessage
  -- >   deriving (Generic, ViewAction)
  data Action id


  -- | Include any child hyperviews here. The compiler will make sure that the page knows how to handle them
  --
  -- > type Require = '[ChildView]
  type Require id :: [Type]


  type Require id = '[]


  -- | Specify how the view should be updated for each Action
  --
  -- > update (SetMessage msg) = pure $ messageView msg
  -- > update ClearMessage = pure $ messageView ""
  update :: (Hyperbole :> es) => Action id -> Eff (Reader id : es) (View id ())


-- | The top-level view returned by a 'Page'. It carries a type-level list of every 'HyperView' used in our 'Page' so the compiler can check our work and wire everything together.
data Root (views :: [Type]) = Root
  deriving (Generic, ViewId)


instance HyperView (Root views) es where
  data Action (Root views) = RootNone
    deriving (Generic, ViewAction)
  type Require (Root views) = views
  update _ = pure none