Counter.purs

module Counter  where

import Prelude (Unit(), pure, unit, ($), bind, show, void, (++), (+), (*), (<$>), const, negate, id)
import Data.Functor ((<$))
import Control.Monad.Aff (Aff(), runAff)
import Control.Monad.Eff (Eff())
import Control.Monad.Eff.Exception (throwException)
import Control.Monad.Eff.Class (liftEff)
import Halogen (HalogenEffects(), ComponentDSL(), Natural(), ComponentHTML(), Component(), action, runUI, component, set)
import Halogen.Util (appendToBody, onLoad)
import Halogen.HTML.Indexed (text)
import Signal ((<~), (~>), runSignal, foldp, sampleOn, filter )
import Signal.DOM (CoordinatePair(), mousePos, mouseButton )
import Signal.Time (second, every, now)

type State = Int

data Query a = SetState State a

type Effects = HalogenEffects ()

ui :: Component State Query (Aff Effects)
ui = component render eval

  where

    render :: State -> ComponentHTML Query
    render s = text (show s)

    eval :: Natural Query (ComponentDSL State Query (Aff Effects))
    eval (SetState s next) = next <$ do
        set s

main :: forall eff . Eff Effects Unit
main = runAff throwException pure $ void do
    app <- runUI ui 0
    let update p = runAff throwException pure $ app.driver (action (SetState p))
    onLoad $ appendToBody app.node
    liftEff do
        let button index delta = do
                button <- mouseButton index
                pure $ (const delta <~ filter id true button)
        plus <- button 0 1
        minus <- button 2 (negate 1)
        runSignal $ update <~ foldp (+) 0 (plus ++ minus)