withoutAlgebra.purs

module Button where

import Prelude
import Data.Maybe (Maybe(..))
import Halogen as H
import Halogen.HTML as HH
import Halogen.HTML.Events as HE
import Halogen.HTML.Properties as HP

type State = Boolean

data Input = Request | DoNothing
data Message = Toggled Boolean | Response Boolean
data Inner = Clicked

type Slot = H.Slot Message

myButton :: forall m. H.Component HH.HTML Input Message m
myButton =
  H.component
    { initialState: \_ -> false
    , render
    , eval
    }
  where

  initialState :: State
  initialState = false

  render :: State -> H.ComponentHTML Inner () m
  render state =
    let
      label = if state then "On" else "Off"
    in
      HH.button
        [ HP.title label
        , HE.onClick Toggle 
        ]
        [ HH.text label ]

  eval :: H.HalogenQ Input Inner -> H.HalogenM Inner State () Message m Unit
  eval = case _ of
    Initialize _ -> 
      pure unit
    Finalize -> 
      pure unit
    Handle _ -> do 
      H.modify_ not
      st <- H.get 
      H.raise $ Toggled st 
    Receive Request -> do 
      st <- H.get 
      H.raise $ Response st 


----------------------------------------------------------------------------
module Container where

import Prelude

import Button as Button
import Data.Maybe (Maybe(..), maybe)
import Data.Symbol (SProxy(..))
import Halogen as H
import Halogen.HTML as HH
import Halogen.HTML.Events as HE

data Handle = HandleButton Button.Message | CheckButtonState

type State =
  { toggleCount :: Int
  , buttonState :: Maybe Boolean
  }

type ChildSlots =
  ( button :: Button.Slot
  )

_button :: SProxy "button"
_button = SProxy

component :: forall m. H.Component HH.HTML Void Void m
component =
  H.component
    { initialState: const initialState
    , render
    , eval
    }
  where

  initialState :: State
  initialState =
    { toggleCount: 0
    , buttonState: Nothing
    }

  render :: State -> H.ComponentHTML Inner ChildSlots m
  render state =
    HH.div_
      [ HH.slot _button unit Button.myButton Button.DoNothing HandleButton
      , HH.p_
          [ HH.text ("Button has been toggled " <> show state.toggleCount <> " time(s)") ]
      , HH.p_
          [ HH.text
              $ "Last time I checked, the button was: "
              <> (maybe "(not checked yet)" (if _ then "on" else "off") state.buttonState)
              <> ". "
          , HH.button
              [ HE.onClick CheckButtonState ]
              [ HH.text "Check now" ]
          ]
      ]

  eval :: H.HalogenQ Void Void -> H.HalogenM Void State ChildSlots Void m Unit
  eval = case _ of
    Initialize _ -> pure unit
    Finalize -> pure unit
    Handle (HandleButton msg) -> case msg of 
      Response b -> H.modify_ _{ buttonState = Just b }
      _ -> pure unit
    Handle CheckButtonState -> H.send _button Button.Request
    Receive _ -> pure unit