Add useAffReducer

src/React/Basic/Hooks/Aff.purs

@@ -1,15 +1,21 @@
 module React.Basic.Hooks.Aff
   ( useAff
   , UseAff
+  , useAffReducer
+  , AffReducer
+  , noEffects
+  , UseAffReducer
   ) where
 
 import Prelude
 import Data.Either (Either(..))
+import Data.Foldable (for_)
 import Data.Maybe (Maybe(..))
 import Data.Newtype (class Newtype)
+import Effect (Effect)
 import Effect.Aff (Aff, Error, error, killFiber, launchAff, launchAff_, throwError, try)
 import Effect.Class (liftEffect)
-import React.Basic.Hooks (Hook, UseEffect, UseState, coerceHook, unsafeRenderEffect, useEffect, useState, (/\))
+import React.Basic.Hooks (type (/\), Hook, UnsafeReference(..), UseEffect, UseReducer, UseState, coerceHook, unsafeRenderEffect, useEffect, useReducer, useState, (/\))
 import React.Basic.Hooks as React
 
 -- | `useAff` is used for asynchronous effects or `Aff`. The asynchronous effect
@@ -48,3 +54,61 @@ newtype UseAff deps a hooks
   = UseAff (UseEffect deps (UseState (Maybe (Either Error a)) hooks))
 
 derive instance ntUseAff :: Newtype (UseAff deps a hooks) _
+
+-- | Provide an initial state and a reducer function. This is a more powerful
+-- | version of `useReducer`, where a state change can additionally queue
+-- | asynchronous operations. The results of those operations must be  mapped
+-- | into the reducer's `action` type. This is essentially the Elm architecture.
+-- |
+-- | Generally, I recommend `useAff` paired with tools like `useResetToken` over
+-- | `useAffReducer` as there are many ways `useAffReducer` can result in race
+-- | conditions. `useAff` with proper dependency management will handle previous
+-- | request cancellation and ensure your `Aff` result is always in sync with
+-- | the provided `deps`, for example. To accomplish the same thing with
+-- | `useAffReducer` would require tracking `Fiber`s manually in your state
+-- | somehow.. :c
+-- |
+-- | That said, `useAffReducer` can still be helpful when converting from the
+-- | current `React.Basic` (non-hooks) API or for those used to Elm.
+-- |
+-- | *Note: Aff failures are thrown. If you need to capture an error state, be
+-- |   sure to capture it in your action type!*
+useAffReducer ::
+  forall state action.
+  state ->
+  AffReducer state action ->
+  Hook (UseAffReducer state action) (state /\ (action -> Effect Unit))
+useAffReducer initialState reducer =
+  coerceHook React.do
+    { state, effects } /\ dispatch <-
+      useReducer { state: initialState, effects: [] } (_.state >>> reducer)
+    useEffect (UnsafeReference effects) do
+      for_ effects \aff ->
+        launchAff_ do
+          actions <- aff
+          liftEffect do for_ actions dispatch
+      mempty
+    pure (state /\ dispatch)
+
+type AffReducer state action
+  = state ->
+    action ->
+    { state :: state
+    , effects :: Array (Aff (Array action))
+    }
+
+noEffects ::
+  forall state action.
+  state ->
+  { state :: state
+  , effects :: Array (Aff (Array action))
+  }
+noEffects state = { state, effects: [] }
+
+newtype UseAffReducer state action hooks
+  = UseAffReducer
+  ( UseEffect (UnsafeReference (Array (Aff (Array action))))
+      (UseReducer { state :: state, effects :: Array (Aff (Array action)) } action hooks)
+  )
+
+derive instance ntUseAffReducer :: Newtype (UseAffReducer state action hooks) _