Automatically update options in local configuration file

src/config.js

@@ -1,23 +1,54 @@
 'use strict';
-const {readFileSync} = require('fs');
-const {ensureFileSync} = require('./util');
+const fs = require('fs');
 const defaultConfig = require('./configs');
 const file = require('./file');
 
 const {log} = console;
 
 class Config {
+  constructor() {
+    this._default = Object.assign({}, defaultConfig);
+  }
+
+  get _local() {
+    try {
+      return JSON.parse(fs.readFileSync(file.localConfig, 'utf8'));
+    } catch (error) {
+      return log(error);
+    }
+  }
+
+  get configuration() {
+    this._ensureLocalConfig(file.localConfig);
+    return this._local;
+  }
+
   get shortcutKeys() {
-    return this._load.shortcutKeys;
+    return this.configuration.shortcutKeys;
   }
 
-  get _load() {
-    ensureFileSync(file.localConfig, JSON.stringify(defaultConfig, null, 4));
+  _updateConfig(data) {
+    const result = Object.assign({}, this._default);
+
+    Object.keys(data).forEach(type => {
+      result[type] = Object.assign({}, result[type], data[type]);
+    });
+
+    Object.keys(result).forEach(type => {
+      const [opts, defaultOpts] = [data[type], this._default[type]].map(Object.keys);
+      const deprecated = opts.filter(x => !defaultOpts.includes(x));
+      deprecated.forEach(x => delete result[type][x]);
+    });
 
+    return result;
+  }
+
+  _ensureLocalConfig(path) {
+    const data = fs.existsSync(path) ? this._updateConfig(this._local) : this._default;
     try {
-      return JSON.parse(readFileSync(file.localConfig, 'utf8'));
+      fs.writeFileSync(path, JSON.stringify(data, null, 4));
     } catch (error) {
-      return log(error);
+      log(error);
     }
   }
 }