Provider config and cli-based setup

lib/config.js

@@ -0,0 +1,40 @@
+import fs from 'fs';
+
+export class Config {
+  
+  constructor(path:string, data:object = {}) {
+    this.path = path;
+    this.data = data;
+  }
+  
+  get(key:string) {
+    this.validateKey(key);
+    let [providerName, keyName] = key.split(".");
+    return this.data[providerName] && this.data[providerName][keyName];
+  }
+  
+  set(key:string, value:object) {
+    this.validateKey(key);
+    let [providerName, keyName] = key.split(".");
+    this.data[providerName] = this.data[providerName] || {};
+    this.data[providerName][keyName] = value;
+    this.save();
+  }
+  
+  validateKey(key:string) {
+    if (key.split(".").length != 2)
+      throw new Error(`The config key '${key}' is invalid. Configuration keys must be in the form [my-provider].[myKey]`);
+  }
+  
+  static load(configPath: string): Config {
+    // load up the previous config if found
+    if (fs.existsSync(configPath))
+      return new Config(configPath, JSON.parse(fs.readFileSync(configPath)));
+    else
+      return new Config(configPath); // empty initial config
+  }
+  
+  save() {
+    fs.writeFileSync(this.path, JSON.stringify(this.data, null, 2));
+  }
+}