createReducer utility

Author: Asaf Shakarzy

README.md

@@ -1,7 +1,14 @@
 # `redux-immutablejs`
 
-An alternative to [combineReducers](http://rackt.github.io/redux/docs/api/combineReducers.html) that supports
-[ImmutableJs](https://facebook.github.io/immutable-js/).
+Redux & Immutable integration
+
+This is a small library that aims to provide integration tools between [Redux](https://github.com/rackt/redux)
+& [ImmutableJs](https://facebook.github.io/immutable-js/) that fully conforms Redux _actions_ & _reducers_ standards.
+
+1. An alternative to [combineReducers](http://rackt.github.io/redux/docs/api/combineReducers.html) that supports
+[ImmutableJs](https://facebook.github.io/immutable-js/) for store initial state.
+1. An optional handler map reducer creator with immutable support.
+
 
 # Setup
 
@@ -23,6 +30,36 @@ const state = reducer(state);
 export default createStore(reducer, state);
 ```
 
+## Immutable Handler Map reducer creator
+
+Using `createReducer` is an optional function that creates a reducer from a collection of handlers, except
+getting ride of the _switch_ statement, it also provides the following benefits:
+
+1. If the given `initialState` type is mutated, it will get converted to an immutable type.
+1. An error is produced in case a reducer handler returns a mutated state (not recommended but this behavior can be disabled)
+
+```js
+import { createReducer } from 'redux-immutablejs'
+const initialState = Immutable.fromJS({ isAuth: false })
+
+/**
+ * Reducer domain that handles authentication & authorization.
+ **/
+export default createReducer(initialState, {
+  [LOGIN] (state, action) {
+    return state.merge({ 'isAuth': true, token: action.payload.token })
+  },
+
+  [LOGOUT] (domain) {
+    return domain.merge({ 'isAuth': false, 'current_identity': {}, token: undefined })
+  }
+})
+```
+
+
+Please note that this is optional and `combineReducers` should work just fine if you prefer the old `switch` way.
+
+
 # FAQ
 
 ## How this library is different from 'redux-immutable' ?

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "redux-immutable",
+  "name": "redux-immutablejs",
   "version": "0.0.1",
   "description": "Redux Immutable facilities",
   "scripts": {
@@ -14,7 +14,7 @@
   "author": "Indexia Tech",
   "license": "BSD-3-Clause",
   "bugs": {
-    "url": "https://github.com/indexiatech/redux-immutable/issues"
+    "url": "https://github.com/indexiatech/redux-immutablejs/issues"
   },
   "homepage": "http://indexiatech.github.io/redux-immutable",
   "peerDependencies": {

src/index.js

@@ -1,5 +1,7 @@
 import combineReducers from './utils/combineReducers';
+import createReducer from './utils/createReducer';
 
 export {
-  combineReducers
-}
+  combineReducers,
+  createReducer
+};

src/utils/createReducer.js

@@ -0,0 +1,34 @@
+import Immutable from 'immutable';
+
+/**
+ * Create a handler (action) map reducer for the given list of handlers
+ *
+ * @param  {object} initialState     The initial state of the reducer, expecting an Immutable.Iterable instance,
+ * otherwise given initialState is converted to immutable.
+ * @param  {object} handlers         A map of actions where key is action name and value is a reducer function
+ * @param  {boolean} enforceImmutable = true if to enforce immutable, in other words a TypeError is thrown in case
+ * a handler returned anything that is not an Immutable.Iterable type.
+ * @return {object}                  The calculated next state
+ */
+export default function createReducer(initialState, handlers, enforceImmutable = true) {
+  return (state = initialState, action) => {
+    // convert the initial state to immutable
+    if (!Immutable.Iterable.isIterable) {
+     state = Immutable.fromJS(state);
+    }
+
+    const handler = (action && action.type) ? handlers[action.type] : undefined;
+
+    if (!handler) {
+      return state;
+    }
+
+    state = handler(state, action);
+
+    if (enforceImmutable && !Immutable.Iterable.isIterable(state)) {
+      throw new TypeError('Reducers must return Immutable objects.');
+    }
+
+    return state;
+  };
+}