Register Internal and Custom backend API's (#1011)

* allow backend register

* handle multiple backends, including internal

src/backends/backend.js

@@ -14,6 +14,15 @@ import { sanitizeSlug } from "Lib/urlHelper";
 import TestRepoBackend from "./test-repo/implementation";
 import GitHubBackend from "./github/implementation";
 import GitGatewayBackend from "./git-gateway/implementation";
+import { registerBackend, getBackend } from 'Lib/registry';
+
+/**
+ * Register internal backends
+ */
+registerBackend('git-gateway', GitGatewayBackend);
+registerBackend('github', GitHubBackend);
+registerBackend('test-repo', TestRepoBackend);
+
 
 class LocalStorageAuthStore {
   storageKey = "netlify-cms-user";
@@ -339,15 +348,10 @@ export function resolveBackend(config) {
 
   const authStore = new LocalStorageAuthStore();
 
-  switch (name) {
-    case "test-repo":
-      return new Backend(new TestRepoBackend(config), name, authStore);
-    case "github":
-      return new Backend(new GitHubBackend(config), name, authStore);
-    case "git-gateway":
-      return new Backend(new GitGatewayBackend(config), name, authStore);
-    default:
-      throw new Error(`Backend not found: ${ name }`);
+  if (!getBackend(name)) {
+    throw new Error(`Backend not found: ${ name }`);
+  } else {
+    return new Backend(getBackend(name).init(config), name, authStore);
   }
 }
 

src/lib/registry.js

@@ -5,6 +5,7 @@ import { newEditorPlugin } from 'EditorWidgets/Markdown/MarkdownControl/plugins'
  * Global Registry Object
  */
 const registry = {
+  backends: { },
   templates: {},
   previewStyles: [],
   widgets: {},
@@ -24,6 +25,8 @@ export default {
   getEditorComponents,
   registerWidgetValueSerializer,
   getWidgetValueSerializer,
+  registerBackend,
+  getBackend,
 };
 
 
@@ -87,3 +90,23 @@ export function registerWidgetValueSerializer(widgetName, serializer) {
 export function getWidgetValueSerializer(widgetName) {
   return registry.widgetValueSerializers[widgetName];
 };
+
+/**
+ * Backend API
+ */
+export function registerBackend(name, BackendClass) {
+  if (!name || !BackendClass) {
+    console.error("Backend parameters invalid. example: CMS.registerBackend('myBackend', BackendClass)");
+  } else if (registry.backends[name]) {
+      console.error(`Backend [${ name }] already registered. Please choose a different name.`);
+  } else {
+    registry.backends[name] = {
+      init: config => new BackendClass(config),
+    };
+  }
+}
+
+export function getBackend(name) {
+  return registry.backends[name];
+}
+