From 2b30566ad3a25d0e4267ac1050487b20073a1f0a Mon Sep 17 00:00:00 2001
From: Marcel Tinner <m1tinner@gmail.com>
Date: Wed, 23 Oct 2019 15:13:22 +0200
Subject: [PATCH 1/2] add typings for createReducer

---
 src/createReducer.ts | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/src/createReducer.ts b/src/createReducer.ts
index 781900f45a..cee9ba867d 100644
--- a/src/createReducer.ts
+++ b/src/createReducer.ts
@@ -1,18 +1,35 @@
 import { useCallback, useRef, useState } from 'react';
 import useUpdateEffect from './useUpdateEffect';
 
-function composeMiddleware(chain) {
-  return (context, dispatch) => {
+type Dispatch<Action> = (action: Action) => void;
+
+type Store<Action, State> = {
+  getState: () => State;
+  dispatch: Dispatch<Action>;
+};
+
+type Middleware<Action, State> = (
+  store: Store<Action, State>
+) => (next: Dispatch<Action>) => (action: Action) => void;
+
+function composeMiddleware<Action, State>(chain: Middleware<Action, State>[]) {
+  return (context: Store<Action, State>, dispatch: Dispatch<Action>) => {
     return chain.reduceRight((res, middleware) => {
       return middleware(context)(res);
     }, dispatch);
   };
 }
 
-const createReducer = (...middlewares) => {
-  const composedMiddleware = composeMiddleware(middlewares);
+const createReducer = <Action, State>(
+  ...middlewares: Middleware<Action, State>[]
+) => {
+  const composedMiddleware = composeMiddleware<Action, State>(middlewares);
 
-  return (reducer, initialState, initializer = value => value) => {
+  return (
+    reducer: (state: State, action: Action) => State,
+    initialState: State,
+    initializer = (value: State) => value
+  ): [State, Dispatch<Action>] => {
     const ref = useRef(initializer(initialState));
     const [, setState] = useState(ref.current);
 
@@ -25,11 +42,11 @@ const createReducer = (...middlewares) => {
       [reducer]
     );
 
-    const dispatchRef = useRef(
+    const dispatchRef: { current: Dispatch<Action> } = useRef(
       composedMiddleware(
         {
           getState: () => ref.current,
-          dispatch: (...args) => dispatchRef.current(...args),
+          dispatch: (...args: [Action]) => dispatchRef.current(...args)
         },
         dispatch
       )
@@ -39,7 +56,7 @@ const createReducer = (...middlewares) => {
       dispatchRef.current = composedMiddleware(
         {
           getState: () => ref.current,
-          dispatch: (...args) => dispatchRef.current(...args),
+          dispatch: (...args: [Action]) => dispatchRef.current(...args)
         },
         dispatch
       );

From 0c20fb98fa3b93d2674a21a4b63e191af64e8bd1 Mon Sep 17 00:00:00 2001
From: Marcel <m1tinner@gmail.com>
Date: Thu, 24 Oct 2019 07:06:54 +0200
Subject: [PATCH 2/2] change dispatchRef to mutableRefObject

---
 src/createReducer.ts | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/src/createReducer.ts b/src/createReducer.ts
index cee9ba867d..7cece51cbc 100644
--- a/src/createReducer.ts
+++ b/src/createReducer.ts
@@ -1,18 +1,16 @@
-import { useCallback, useRef, useState } from 'react';
+import { MutableRefObject, useCallback, useRef, useState } from 'react';
 import useUpdateEffect from './useUpdateEffect';
 
 type Dispatch<Action> = (action: Action) => void;
 
-type Store<Action, State> = {
+interface Store<Action, State> {
   getState: () => State;
   dispatch: Dispatch<Action>;
-};
+}
 
-type Middleware<Action, State> = (
-  store: Store<Action, State>
-) => (next: Dispatch<Action>) => (action: Action) => void;
+type Middleware<Action, State> = (store: Store<Action, State>) => (next: Dispatch<Action>) => (action: Action) => void;
 
-function composeMiddleware<Action, State>(chain: Middleware<Action, State>[]) {
+function composeMiddleware<Action, State>(chain: Array<Middleware<Action, State>>) {
   return (context: Store<Action, State>, dispatch: Dispatch<Action>) => {
     return chain.reduceRight((res, middleware) => {
       return middleware(context)(res);
@@ -20,9 +18,7 @@ function composeMiddleware<Action, State>(chain: Middleware<Action, State>[]) {
   };
 }
 
-const createReducer = <Action, State>(
-  ...middlewares: Middleware<Action, State>[]
-) => {
+const createReducer = <Action, State>(...middlewares: Array<Middleware<Action, State>>) => {
   const composedMiddleware = composeMiddleware<Action, State>(middlewares);
 
   return (
@@ -42,11 +38,11 @@ const createReducer = <Action, State>(
       [reducer]
     );
 
-    const dispatchRef: { current: Dispatch<Action> } = useRef(
+    const dispatchRef: MutableRefObject<Dispatch<Action>> = useRef(
       composedMiddleware(
         {
           getState: () => ref.current,
-          dispatch: (...args: [Action]) => dispatchRef.current(...args)
+          dispatch: (...args: [Action]) => dispatchRef.current(...args),
         },
         dispatch
       )
@@ -56,7 +52,7 @@ const createReducer = <Action, State>(
       dispatchRef.current = composedMiddleware(
         {
           getState: () => ref.current,
-          dispatch: (...args: [Action]) => dispatchRef.current(...args)
+          dispatch: (...args: [Action]) => dispatchRef.current(...args),
         },
         dispatch
       );