From 7554b9a61eb9b4744b9feb113775ff538b16beaf Mon Sep 17 00:00:00 2001
From: Ayush Goyal <ayush987goyal@gmail.com>
Date: Sat, 18 Jan 2020 08:16:38 +0530
Subject: [PATCH] feat: add useMethods state hook

---
 docs/useMethods.md           | 48 +++++++++++++++++++++
 src/index.ts                 |  1 +
 src/useMethods.ts            | 33 +++++++++++----
 stories/useMethods.story.tsx | 38 +++++++++++++++++
 tests/useMethods.test.ts     | 81 ++++++++++++++++++++++++++++++++++++
 5 files changed, 192 insertions(+), 9 deletions(-)
 create mode 100644 docs/useMethods.md
 create mode 100644 stories/useMethods.story.tsx
 create mode 100644 tests/useMethods.test.ts

diff --git a/docs/useMethods.md b/docs/useMethods.md
new file mode 100644
index 0000000000..718f80e617
--- /dev/null
+++ b/docs/useMethods.md
@@ -0,0 +1,48 @@
+# `useMethods`
+
+React hook that simplifies the `useReducer` implementation.
+
+## Usage
+
+```jsx
+import { useMethods } from 'react-use';
+
+const initialState = {
+  count: 0,
+};
+
+function createMethods(state) {
+  return {
+    reset() {
+      return initialState;
+    },
+    increment() {
+      return { ...state, count: state.count + 1 };
+    },
+    decrement() {
+      return { ...state, count: state.count - 1 };
+    },
+  };
+}
+
+const Demo = () => {
+  const [state, methods] = useMethods(createMethods, initialState);
+
+  return (
+    <>
+      <p>Count: {state.count}</p>
+      <button onClick={methods.decrement}>-</button>
+      <button onClick={methods.increment}>+</button>
+    </>
+  );
+};
+```
+
+## Reference
+
+```js
+const [state, methods] = useMethods(createMethods, initialState);
+```
+
+- `createMethods` &mdash; function that takes current state and return an object containing methods that return updated state.
+- `initialState` &mdash; initial value of the state.
diff --git a/src/index.ts b/src/index.ts
index 64828fb1c6..70e290a965 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -53,6 +53,7 @@ export { default as useMap } from './useMap';
 export { default as useMedia } from './useMedia';
 export { default as useMediaDevices } from './useMediaDevices';
 export { useMediatedState } from './useMediatedState';
+export { default as useMethods } from './useMethods';
 export { default as useMotion } from './useMotion';
 export { default as useMount } from './useMount';
 export { default as useMountedState } from './useMountedState';
diff --git a/src/useMethods.ts b/src/useMethods.ts
index 9b29d99147..8483f7ba7a 100644
--- a/src/useMethods.ts
+++ b/src/useMethods.ts
@@ -1,23 +1,38 @@
-/* eslint-disable */
-import { useMemo, useReducer } from 'react';
+import { useMemo, useReducer, Reducer } from 'react';
 
-const useMethods = (createMethods, initialState) => {
-  const reducer = useMemo(
-    () => (reducerState, action) => {
+type Action = {
+  type: string;
+  payload?: any;
+};
+
+type CreateMethods<M, T> = (
+  state: T
+) => {
+  [P in keyof M]: (payload?: any) => T;
+};
+
+type WrappedMethods<M> = {
+  [P in keyof M]: (...payload: any) => void;
+};
+
+const useMethods = <M, T>(createMethods: CreateMethods<M, T>, initialState: T): [T, WrappedMethods<M>] => {
+  const reducer = useMemo<Reducer<T, Action>>(
+    () => (reducerState: T, action: Action) => {
       return createMethods(reducerState)[action.type](...action.payload);
     },
     [createMethods]
   );
 
-  const [state, dispatch] = useReducer(reducer, initialState);
+  const [state, dispatch] = useReducer<Reducer<T, Action>>(reducer, initialState);
 
-  const wrappedMethods = useMemo(() => {
+  const wrappedMethods: WrappedMethods<M> = useMemo(() => {
     const actionTypes = Object.keys(createMethods(initialState));
+
     return actionTypes.reduce((acc, type) => {
       acc[type] = (...payload) => dispatch({ type, payload });
       return acc;
-    }, {});
-  }, []);
+    }, {} as WrappedMethods<M>);
+  }, [createMethods]);
 
   return [state, wrappedMethods];
 };
diff --git a/stories/useMethods.story.tsx b/stories/useMethods.story.tsx
new file mode 100644
index 0000000000..8104297cd6
--- /dev/null
+++ b/stories/useMethods.story.tsx
@@ -0,0 +1,38 @@
+import { storiesOf } from '@storybook/react';
+import * as React from 'react';
+import { useMethods } from '../src';
+import ShowDocs from './util/ShowDocs';
+
+const initialState = {
+  count: 0,
+};
+
+function createMethods(state) {
+  return {
+    reset() {
+      return initialState;
+    },
+    increment() {
+      return { ...state, count: state.count + 1 };
+    },
+    decrement() {
+      return { ...state, count: state.count - 1 };
+    },
+  };
+}
+
+const Demo = () => {
+  const [state, methods] = useMethods(createMethods, initialState);
+
+  return (
+    <>
+      <p>Count: {state.count}</p>
+      <button onClick={methods.decrement}>-</button>
+      <button onClick={methods.increment}>+</button>
+    </>
+  );
+};
+
+storiesOf('State|useMethods', module)
+  .add('Docs', () => <ShowDocs md={require('../docs/useMethods.md')} />)
+  .add('Demo', () => <Demo />);
diff --git a/tests/useMethods.test.ts b/tests/useMethods.test.ts
new file mode 100644
index 0000000000..c34394e3cc
--- /dev/null
+++ b/tests/useMethods.test.ts
@@ -0,0 +1,81 @@
+import { renderHook, act } from '@testing-library/react-hooks';
+import { useMethods } from '../src';
+
+it('should have initialState value as the returned state value', () => {
+  const initialState = {
+    count: 10,
+  };
+
+  const createMethods = state => ({
+    doStuff: () => state,
+  });
+
+  const { result } = renderHook(() => useMethods(createMethods, initialState));
+
+  expect(result.current[0]).toEqual(initialState);
+});
+
+it('should return wrappedMethods object containing all the methods defined in createMethods', () => {
+  const initialState = {
+    count: 10,
+  };
+
+  const createMethods = state => ({
+    reset() {
+      return initialState;
+    },
+    increment() {
+      return { ...state, count: state.count + 1 };
+    },
+    decrement() {
+      return { ...state, count: state.count - 1 };
+    },
+  });
+
+  const { result } = renderHook(() => useMethods(createMethods, initialState));
+
+  for (const key of Object.keys(createMethods(initialState))) {
+    expect(result.current[1][key]).toBeDefined();
+  }
+});
+
+it('should properly update the state based on the createMethods', () => {
+  const count = 10;
+  const initialState = {
+    count,
+  };
+
+  const createMethods = state => ({
+    reset() {
+      return initialState;
+    },
+    increment() {
+      return { ...state, count: state.count + 1 };
+    },
+    decrement() {
+      return { ...state, count: state.count - 1 };
+    },
+  });
+
+  const { result } = renderHook(() => useMethods(createMethods, initialState));
+
+  act(() => {
+    result.current[1].increment();
+  });
+  expect(result.current[0].count).toBe(count + 1);
+
+  act(() => {
+    result.current[1].decrement();
+  });
+  expect(result.current[0].count).toBe(count);
+
+  act(() => {
+    result.current[1].decrement();
+  });
+  expect(result.current[0].count).toBe(count - 1);
+
+  act(() => {
+    result.current[1].reset();
+  });
+  expect(result.current[0].count).toBe(count);
+});