feat: add working store implementation

.eslintrc

@@ -1,7 +1,7 @@
 {
   "parserOptions": {
-    "ecmaVersion": 8,
+    "ecmaVersion": 9,
-    "sourceType": "script"
+    "sourceType": "module"
   },
   "extends": [
     "airbnb",

index.js

@@ -1,3 +1,3 @@
-const mod = require('./src/index.js');
+const mod = require('./dist/index.js');
 
 module.exports = mod;

src/index.js

@@ -1,3 +0,0 @@
-module.exports = function mod() {
-  // module code goes here
-};

src/index.mjs

@@ -0,0 +1,121 @@
+/* eslint no-param-reassign: 0, react/destructuring-assignment: 0, react/no-multi-comp: 0 */
+import React, { createContext, useContext } from 'react';
+import PropTypes from 'prop-types';
+import { produce, original } from 'immer';
+
+// keep track of all the stores
+const stores = new Map();
+
+// USAGE: createStore('myStore', { state, mutations, actions, getters })
+export function createStore(name, storeSpec) {
+  // don't duplicate stores
+  if (stores.has(name)) throw new Error(`Store '${name}' already exists`);
+
+  const spec = {
+    state: {},
+    mutations: {},
+    actions: {},
+    getters: {},
+    ...storeSpec,
+  };
+
+  // create a new context for the store and add it to the map
+  const storeContext = createContext({
+    state: spec.state,
+    commit: () => {},
+    dispatch: () => {},
+    getters: () => {},
+  });
+
+  stores.set(name, {
+    context: storeContext,
+    provider: class StoreProvider extends React.Component {
+      static propTypes = {
+        children: PropTypes.node.isRequired,
+      };
+
+      state = {
+        state: spec.state,
+        commit: (n, ...args) => {
+          const mutation = spec.mutations[n];
+          if (!mutation) throw new Error(`No such mutation: ${n}`);
+          this.setState(
+            produce(draft => {
+              mutation({ state: draft.state, original }, ...args);
+            })
+          );
+        },
+        dispatch: async (n, ...args) => {
+          const action = spec.actions[n];
+          if (!action) throw new Error(`No such action: ${n}`);
+          return produce(this.state.state, async draft => {
+            // NOTE: this does not change state, it's expected that
+            // actions use commit to update the state
+            return action({ state: draft, commit: this.state.commit }, ...args);
+          });
+        },
+        get: (n, ...args) => {
+          const getter = spec.getters[n];
+          if (!getter) throw new Error(`No such getter: ${n}`);
+          return getter(this.state.state, ...args);
+        },
+      };
+
+      render() {
+        return React.createElement(
+          storeContext.Provider,
+          { value: this.state },
+          this.props.children
+        );
+      }
+    },
+    // TODO: keep track of the intial state, for resetting
+    // initialState: { ...spec.state },
+  });
+}
+
+// TODO: method to build a larger state object made of stores
+// composeStores({
+//   todos: todoStore
+// });
+
+// hook to access a specific store and read/write methods
+// USAGE: const { state, commit } = useStore('myStore')
+export function useStore(name) {
+  if (!stores.has(name)) throw new Error(`Store does not exist: '${name}'`);
+  const store = stores.get(name);
+  return useContext(store.context);
+}
+
+// provider to wrap your app or component
+export class StateProvider extends React.Component {
+  static propTypes = {
+    children: PropTypes.node.isRequired,
+    names: PropTypes.string,
+  };
+
+  static defaultProps = {
+    names: '',
+  };
+
+  render() {
+    const { names, children } = this.props;
+    const namesArray = names.length ? names.split(',') : [];
+
+    // provide all stores if none are specified
+    const provideAllStores = namesArray.length === 0;
+
+    // build an array of all the store providers
+    const providers = provideAllStores
+      ? Array.from(stores).map(([, store]) => store.provider)
+      : namesArray.map(name => {
+          if (!stores.has(name)) throw new Error(`Store does not exist: '${name}'`);
+          return stores.get(name).provider;
+        });
+
+    // nest children inside all of the providers
+    return providers.reduce((acc, provider) => {
+      return React.createElement(provider, {}, acc);
+    }, children);
+  }
+}