From 00958737363f80d957a73ae3533bd260f0172597 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Tue, 9 Mar 2021 11:16:10 +0100
Subject: [PATCH] core-api: migrate AppContext to use version bridge

Co-authored-by: Juan Lulkin <jmaiz@spotify.com>
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
---
 packages/core-api/package.json                |  1 +
 packages/core-api/src/app/AppContext.test.tsx | 79 +++++++++++++++++++
 packages/core-api/src/app/AppContext.tsx      | 41 +++++++---
 3 files changed, 111 insertions(+), 10 deletions(-)
 create mode 100644 packages/core-api/src/app/AppContext.test.tsx

diff --git a/packages/core-api/package.json b/packages/core-api/package.json
index cdc21264d3..dbeb2021df 100644
--- a/packages/core-api/package.json
+++ b/packages/core-api/package.json
@@ -47,6 +47,7 @@
     "@backstage/test-utils-core": "^0.1.1",
     "@testing-library/jest-dom": "^5.10.1",
     "@testing-library/react": "^11.2.5",
+    "@testing-library/react-hooks": "^3.3.0",
     "@testing-library/user-event": "^12.0.7",
     "@types/jest": "^26.0.7",
     "@types/node": "^14.14.32",
diff --git a/packages/core-api/src/app/AppContext.test.tsx b/packages/core-api/src/app/AppContext.test.tsx
new file mode 100644
index 0000000000..55d98c18c0
--- /dev/null
+++ b/packages/core-api/src/app/AppContext.test.tsx
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import React, { useContext, Context } from 'react';
+import { renderHook } from '@testing-library/react-hooks';
+import { VersionedValue } from '../lib/versionedValues';
+import { getGlobalSingleton } from '../lib/globalObject';
+import { AppContext as AppContextV1 } from './types';
+import { AppContextProvider } from './AppContext';
+
+describe('v1 consumer', () => {
+  const AppContext = getGlobalSingleton<
+    Context<VersionedValue<{ 1: AppContextV1 }>>
+  >('app-context');
+
+  function useMockAppV1(): AppContextV1 {
+    const impl = useContext(AppContext)?.atVersion(1);
+    if (!impl) {
+      throw new Error('no impl');
+    }
+    return impl;
+  }
+
+  it('should provide an app context', () => {
+    const mockContext: AppContextV1 = {
+      getComponents: jest.fn(),
+      getSystemIcon: jest.fn(),
+      getPlugins: jest.fn(),
+      getProvider: jest.fn(),
+      getRouter: jest.fn(),
+      getRoutes: jest.fn(),
+    };
+
+    const renderedHook = renderHook(() => useMockAppV1(), {
+      wrapper: ({ children }) => (
+        <AppContextProvider appContext={mockContext} children={children} />
+      ),
+    });
+    const result = renderedHook.result.current;
+
+    expect(mockContext.getComponents).toHaveBeenCalledTimes(0);
+    result.getComponents();
+    expect(mockContext.getComponents).toHaveBeenCalledTimes(1);
+
+    expect(mockContext.getSystemIcon).toHaveBeenCalledTimes(0);
+    result.getSystemIcon('icon');
+    expect(mockContext.getSystemIcon).toHaveBeenCalledTimes(1);
+    expect(mockContext.getSystemIcon).toHaveBeenCalledWith('icon');
+
+    expect(mockContext.getPlugins).toHaveBeenCalledTimes(0);
+    result.getPlugins();
+    expect(mockContext.getPlugins).toHaveBeenCalledTimes(1);
+
+    expect(mockContext.getProvider).toHaveBeenCalledTimes(0);
+    result.getProvider();
+    expect(mockContext.getProvider).toHaveBeenCalledTimes(1);
+
+    expect(mockContext.getRouter).toHaveBeenCalledTimes(0);
+    result.getRouter();
+    expect(mockContext.getRouter).toHaveBeenCalledTimes(1);
+
+    expect(mockContext.getRoutes).toHaveBeenCalledTimes(0);
+    result.getRoutes();
+    expect(mockContext.getRoutes).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/packages/core-api/src/app/AppContext.tsx b/packages/core-api/src/app/AppContext.tsx
index c7c405a959..7b73d71c6b 100644
--- a/packages/core-api/src/app/AppContext.tsx
+++ b/packages/core-api/src/app/AppContext.tsx
@@ -14,26 +14,47 @@
  * limitations under the License.
  */
 
-import React, { createContext, PropsWithChildren, useContext } from 'react';
-import { AppContext } from './types';
+import React, {
+  createContext,
+  PropsWithChildren,
+  useContext,
+  Context,
+} from 'react';
+import {
+  VersionedValue,
+  createVersionedValueMap,
+} from '../lib/versionedValues';
+import { getGlobalSingleton, setGlobalSingleton } from '../lib/globalObject';
+import { AppContext as AppContextV1 } from './types';
 
-const Context = createContext<AppContext | undefined>(undefined);
+type AppContextType = VersionedValue<{ 1: AppContextV1 }> | undefined;
+const AppContext = createContext<AppContextType | undefined>(undefined);
+
+setGlobalSingleton('app-context', AppContext);
 
 type Props = {
-  appContext: AppContext;
+  appContext: AppContextV1;
 };
 
 export const AppContextProvider = ({
   appContext,
   children,
-}: PropsWithChildren<Props>) => (
-  <Context.Provider value={appContext} children={children} />
-);
+}: PropsWithChildren<Props>) => {
+  const versionedValue = createVersionedValueMap({ 1: appContext });
 
-export const useApp = (): AppContext => {
-  const appContext = useContext(Context);
-  if (!appContext) {
+  return <AppContext.Provider value={versionedValue} children={children} />;
+};
+
+export const useApp = (): AppContextV1 => {
+  const versionedContext = useContext(
+    getGlobalSingleton<Context<AppContextType>>('app-context'),
+  );
+  if (!versionedContext) {
     throw new Error('No app context available');
   }
+  const appContext = versionedContext.atVersion(1);
+  if (!appContext) {
+    throw new Error('AppContext v1 not available');
+  }
   return appContext;
 };