From 0d4a12e7f564b9bf1aa5e7d13d995a6cbb4286c0 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Wed, 5 Feb 2020 13:46:00 +0100
Subject: [PATCH] frontend/core: add some kinda app api

---
 frontend/packages/app/src/App.tsx             |  79 +++++++----
 .../app/src/entities/MockEntityCard.tsx       |   9 ++
 .../app/src/entities/MockEntityPage.tsx       |   9 ++
 frontend/packages/app/src/entities/index.ts   |  32 +++++
 frontend/packages/core/package.json           |   2 +
 .../packages/core/src/appApi/AppBuilder.tsx   | 107 +++++++++++++++
 .../packages/core/src/appApi/AppContext.tsx   |  20 +++
 .../core/src/appApi/EntityContext.tsx         |  42 ++++++
 .../packages/core/src/appApi/EntityKind.ts    |   5 +
 .../packages/core/src/appApi/EntityLink.tsx   |  43 ++++++
 .../core/src/appApi/EntityViewPageBuilder.tsx | 124 ++++++++++++++++++
 .../core/src/appApi/OverviewPageBuilder.tsx   |  50 +++++++
 frontend/packages/core/src/appApi/api.ts      |  21 +++
 frontend/packages/core/src/appApi/index.ts    |   5 +
 frontend/packages/core/src/appApi/types.ts    |  36 +++++
 frontend/packages/core/src/index.ts           |   1 +
 16 files changed, 556 insertions(+), 29 deletions(-)
 create mode 100644 frontend/packages/app/src/entities/MockEntityCard.tsx
 create mode 100644 frontend/packages/app/src/entities/MockEntityPage.tsx
 create mode 100644 frontend/packages/app/src/entities/index.ts
 create mode 100644 frontend/packages/core/src/appApi/AppBuilder.tsx
 create mode 100644 frontend/packages/core/src/appApi/AppContext.tsx
 create mode 100644 frontend/packages/core/src/appApi/EntityContext.tsx
 create mode 100644 frontend/packages/core/src/appApi/EntityKind.ts
 create mode 100644 frontend/packages/core/src/appApi/EntityLink.tsx
 create mode 100644 frontend/packages/core/src/appApi/EntityViewPageBuilder.tsx
 create mode 100644 frontend/packages/core/src/appApi/OverviewPageBuilder.tsx
 create mode 100644 frontend/packages/core/src/appApi/api.ts
 create mode 100644 frontend/packages/core/src/appApi/index.ts
 create mode 100644 frontend/packages/core/src/appApi/types.ts

diff --git a/frontend/packages/app/src/App.tsx b/frontend/packages/app/src/App.tsx
index cd85cb85eb..0f22c76671 100644
--- a/frontend/packages/app/src/App.tsx
+++ b/frontend/packages/app/src/App.tsx
@@ -1,19 +1,28 @@
-import React, { FC } from 'react';
+import {
+  BackstageTheme,
+  createApp,
+  EntityLink,
+  Header,
+  InfoCard,
+  Page,
+  theme,
+  withGlobalStyles,
+} from '@backstage/core';
 import helloWorld, { MyComponent } from '@backstage/plugin-hello-world';
-import Typography from '@material-ui/core/Typography';
-import SideBar from './components/SideBar';
 //import PageHeader from './components/PageHeader';
-import { Header, Page, InfoCard } from '@backstage/core';
 import { LoginComponent } from '@backstage/plugin-login';
+import { CssBaseline, makeStyles, ThemeProvider } from '@material-ui/core';
+import Typography from '@material-ui/core/Typography';
+import React, { FC } from 'react';
 import {
   BrowserRouter as Router,
-  Switch,
-  Route,
   Link as RouterLink,
+  Route,
+  Switch,
 } from 'react-router-dom';
-import { BackstageTheme, withGlobalStyles, theme } from '@backstage/core';
-import { CssBaseline, ThemeProvider, makeStyles } from '@material-ui/core';
 import HomePageTimer from './components/HomepageTimer';
+import SideBar from './components/SideBar';
+import entities from './entities';
 
 const useStyles = makeStyles(theme => ({
   root: {
@@ -36,27 +45,6 @@ const useStyles = makeStyles(theme => ({
   },
 }));
 
-const App: FC<{}> = () => {
-  return (
-    <CssBaseline>
-      <ThemeProvider theme={BackstageTheme}>
-        <AppContent>
-          <Router>
-            <Switch>
-              <Route exact path="/">
-                <Home />
-              </Route>
-              <Route path="/login">
-                <Login />
-              </Route>
-            </Switch>
-          </Router>
-        </AppContent>
-      </ThemeProvider>
-    </CssBaseline>
-  );
-};
-
 const Home: FC<{}> = () => {
   return (
     <InfoCard title="Home Page">
@@ -67,6 +55,12 @@ const Home: FC<{}> = () => {
       <MyComponent />
       <div>
         <RouterLink to="/login">Go to Login</RouterLink>
+        <EntityLink kind="service" id="backstage-backend">
+          Backstage Backend
+        </EntityLink>
+        <EntityLink uri="entity:service:backstage-lb" subPath="ci-cd">
+          Backstage LB CI/CD
+        </EntityLink>
       </div>
     </InfoCard>
   );
@@ -103,4 +97,31 @@ const AppShell: FC<{}> = ({ children }) => {
 
 const AppContent = withGlobalStyles(AppShell);
 
+const app = createApp();
+
+app.registerEntityKind(...entities);
+app.setHomePage(Home);
+const AppComponent = app.build();
+
+const App: FC<{}> = () => {
+  return (
+    <CssBaseline>
+      <ThemeProvider theme={BackstageTheme}>
+        <AppContent>
+          <Router>
+            <Switch>
+              <Route path="/login">
+                <Login />
+              </Route>
+              <Route>
+                <AppComponent />
+              </Route>
+            </Switch>
+          </Router>
+        </AppContent>
+      </ThemeProvider>
+    </CssBaseline>
+  );
+};
+
 export default App;
diff --git a/frontend/packages/app/src/entities/MockEntityCard.tsx b/frontend/packages/app/src/entities/MockEntityCard.tsx
new file mode 100644
index 0000000000..97a3f4073d
--- /dev/null
+++ b/frontend/packages/app/src/entities/MockEntityCard.tsx
@@ -0,0 +1,9 @@
+import React, { FC } from 'react';
+import { useEntityUri } from '@backstage/core';
+
+const MockEntityPage: FC<{}> = () => {
+  const uri = useEntityUri();
+  return <span>Mock card for {uri}, replace with some userful plugin</span>;
+};
+
+export default MockEntityPage;
diff --git a/frontend/packages/app/src/entities/MockEntityPage.tsx b/frontend/packages/app/src/entities/MockEntityPage.tsx
new file mode 100644
index 0000000000..091906f31a
--- /dev/null
+++ b/frontend/packages/app/src/entities/MockEntityPage.tsx
@@ -0,0 +1,9 @@
+import React, { FC } from 'react';
+import { useEntityUri } from '@backstage/core';
+
+const MockEntityPage: FC<{}> = () => {
+  const uri = useEntityUri();
+  return <span>Mock page for {uri}, replace with some userful plugin</span>;
+};
+
+export default MockEntityPage;
diff --git a/frontend/packages/app/src/entities/index.ts b/frontend/packages/app/src/entities/index.ts
new file mode 100644
index 0000000000..47c55a3c57
--- /dev/null
+++ b/frontend/packages/app/src/entities/index.ts
@@ -0,0 +1,32 @@
+import {
+  createEntityKind,
+  createOverviewPage,
+  createEntityView,
+} from '@backstage/core';
+import ComputerIcon from '@material-ui/icons/Computer';
+import MockEntityPage from './MockEntityPage';
+import MockEntityCard from './MockEntityCard';
+
+/* SERVICE */
+const serviceOverviewPage = createOverviewPage()
+  .addComponent(MockEntityCard)
+  .addComponent(MockEntityCard);
+
+const serviceView = createEntityView()
+  .addPage('Overview', 'overview', serviceOverviewPage)
+  .addComponent('CI/CD', 'ci-cd', MockEntityPage);
+
+const serviceEntity = createEntityKind({
+  kind: 'service',
+  title: 'Service',
+  color: {
+    primary: '#f00',
+    secondary: '#ba5',
+  },
+  icon: ComputerIcon,
+  pages: {
+    view: serviceView,
+  },
+});
+
+export default [serviceEntity];
diff --git a/frontend/packages/core/package.json b/frontend/packages/core/package.json
index 9c1016141c..b2155fd61a 100644
--- a/frontend/packages/core/package.json
+++ b/frontend/packages/core/package.json
@@ -12,10 +12,12 @@
     "@types/node": "^12.0.0",
     "@types/react": "^16.9.0",
     "@types/react-dom": "^16.9.0",
+    "@types/react-router-dom": "^5.1.3",
     "react": "^16.12.0",
     "react-dom": "^16.12.0",
     "react-helmet":"5.2.1",
     "react-addons-text-content": "0.0.4",
+    "react-router-dom": "^5.1.2",
     "recompose": "0.30.0"
   },
   "scripts": {
diff --git a/frontend/packages/core/src/appApi/AppBuilder.tsx b/frontend/packages/core/src/appApi/AppBuilder.tsx
new file mode 100644
index 0000000000..f9045bbbfd
--- /dev/null
+++ b/frontend/packages/core/src/appApi/AppBuilder.tsx
@@ -0,0 +1,107 @@
+import React, { ComponentType, FC } from 'react';
+import { AppContextProvider } from './AppContext';
+import { App, EntityConfig, AppComponentBuilder } from './types';
+import { Route, Switch, useParams } from 'react-router-dom';
+import EntityKind from './EntityKind';
+import { EntityContextProvider } from './EntityContext';
+
+const DefaultHomePage: FC<{}> = () => {
+  return <span>Hello! I am default home page</span>;
+};
+
+class AppImpl implements App {
+  constructor(private readonly entities: Map<string, EntityKind>) {}
+
+  getEntityConfig(kind: string): EntityConfig {
+    const entity = this.entities.get(kind);
+    if (!entity) {
+      throw new Error('EntityKind not found');
+    }
+    return entity.config;
+  }
+}
+
+function builtComponent(
+  app: App,
+  component: ComponentType<any> | AppComponentBuilder,
+) {
+  if (component instanceof AppComponentBuilder) {
+    return component.build(app);
+  }
+  return component;
+}
+
+export default class AppBuilder {
+  private readonly entities = new Map<string, EntityKind>();
+  private homePage: ComponentType = DefaultHomePage;
+
+  registerEntityKind(...entity: EntityKind[]) {
+    for (const e of entity) {
+      const { kind } = e.config;
+      if (this.entities.has(e.config.kind)) {
+        throw new Error(`EntityKind '${kind}' is already registered`);
+      }
+      this.entities.set(e.config.kind, e);
+    }
+  }
+
+  setHomePage(page: ComponentType<{}>) {
+    this.homePage = page;
+  }
+
+  build(): ComponentType<{}> {
+    const app = new AppImpl(this.entities);
+
+    const entityRoutes = [];
+
+    for (const { config } of this.entities.values()) {
+      const { kind, pages } = config;
+      const basePath = `/entity/${kind}`;
+
+      if (pages.list) {
+        const ListComponent = builtComponent(app, pages.list);
+
+        const Component: FC<{}> = () => (
+          <EntityContextProvider config={config}>
+            <ListComponent />
+          </EntityContextProvider>
+        );
+
+        const path = basePath;
+        entityRoutes.push(
+          <Route key={path} path={path} component={Component} />,
+        );
+      }
+
+      if (pages.view) {
+        const ViewComponent = builtComponent(app, pages.view);
+
+        const Component: FC<{}> = () => {
+          const { entityId } = useParams<{ entityId: string }>();
+          return (
+            <EntityContextProvider config={config} id={entityId}>
+              <ViewComponent />
+            </EntityContextProvider>
+          );
+        };
+
+        const path = `${basePath}/:entityId`;
+        entityRoutes.push(
+          <Route key={path} path={path} component={Component} />,
+        );
+      }
+    }
+
+    const routes = [...entityRoutes];
+
+    return () => (
+      <AppContextProvider app={app}>
+        <Switch>
+          {routes}
+          <Route exact path="/" component={this.homePage} />
+          <Route component={() => <span>404 Not Found</span>} />
+        </Switch>
+      </AppContextProvider>
+    );
+  }
+}
diff --git a/frontend/packages/core/src/appApi/AppContext.tsx b/frontend/packages/core/src/appApi/AppContext.tsx
new file mode 100644
index 0000000000..e8acb424cd
--- /dev/null
+++ b/frontend/packages/core/src/appApi/AppContext.tsx
@@ -0,0 +1,20 @@
+import React, { createContext, useContext, FC } from 'react';
+import { App } from './types';
+
+const Context = createContext<App | undefined>(undefined);
+
+type Props = {
+  app: App;
+};
+
+export const AppContextProvider: FC<Props> = ({ app, children }) => (
+  <Context.Provider value={app} children={children} />
+);
+
+export const useApp = (): App => {
+  const app = useContext(Context);
+  if (!app) {
+    throw new Error('No app context available');
+  }
+  return app;
+};
diff --git a/frontend/packages/core/src/appApi/EntityContext.tsx b/frontend/packages/core/src/appApi/EntityContext.tsx
new file mode 100644
index 0000000000..5efe917f4d
--- /dev/null
+++ b/frontend/packages/core/src/appApi/EntityContext.tsx
@@ -0,0 +1,42 @@
+import React, { createContext, useContext, FC } from 'react';
+import { EntityConfig } from './types';
+
+type Value = {
+  config: EntityConfig;
+  id?: string;
+};
+
+const Context = createContext<Value | undefined>(undefined);
+
+type Props = {
+  config: EntityConfig;
+  id?: string;
+};
+
+export const EntityContextProvider: FC<Props> = ({ config, id, children }) => (
+  <Context.Provider value={{ config, id }} children={children} />
+);
+
+export const useEntity = (): { kind: string; id: string } => {
+  const value = useContext(Context);
+  if (!value) {
+    throw new Error('No entity context available');
+  }
+  if (!value.id) {
+    throw new Error('Entity context does not contain entity id');
+  }
+  return { kind: value.config.kind, id: value.id };
+};
+
+export const useEntityConfig = (): EntityConfig => {
+  const value = useContext(Context);
+  if (!value) {
+    throw new Error('No entity context available');
+  }
+  return value.config;
+};
+
+export const useEntityUri = (): string => {
+  const { kind, id } = useEntity();
+  return `entity:${kind}:${id}`;
+};
diff --git a/frontend/packages/core/src/appApi/EntityKind.ts b/frontend/packages/core/src/appApi/EntityKind.ts
new file mode 100644
index 0000000000..058fdcef6d
--- /dev/null
+++ b/frontend/packages/core/src/appApi/EntityKind.ts
@@ -0,0 +1,5 @@
+import { EntityConfig } from './types';
+
+export default class EntityKind {
+  constructor(readonly config: EntityConfig) {}
+}
diff --git a/frontend/packages/core/src/appApi/EntityLink.tsx b/frontend/packages/core/src/appApi/EntityLink.tsx
new file mode 100644
index 0000000000..c26972c467
--- /dev/null
+++ b/frontend/packages/core/src/appApi/EntityLink.tsx
@@ -0,0 +1,43 @@
+import React, { FC } from 'react';
+import { Link } from 'react-router-dom';
+
+type Props = {
+  subPath?: string;
+} & (
+  | {
+      kind: string;
+      id?: string;
+    }
+  | {
+      uri: string;
+    }
+);
+
+function buildPath(kind: string, id?: string, subPath?: string) {
+  if (id) {
+    if (subPath) {
+      return `/entity/${kind}/${id}/${subPath}`;
+    }
+    return `/entity/${kind}/${id}`;
+  }
+  return `/entity/${kind}`;
+}
+
+const EntityLink: FC<Props> = ({ subPath, children, ...props }) => {
+  if ('kind' in props) {
+    const { kind, id } = props;
+    return <Link to={buildPath(kind, id, subPath)}>{children}</Link>;
+  } else {
+    const match = props.uri.match(/entity:([^:]+)(:[^:]+)?/);
+    if (!match) {
+      throw new TypeError(`Invalid entity uri: '${props.uri}'`);
+    }
+
+    const [, kind, maybeId] = match;
+    const id = maybeId ? maybeId.slice(1) : undefined;
+
+    return <Link to={buildPath(kind, id, subPath)}>{children}</Link>;
+  }
+};
+
+export default EntityLink;
diff --git a/frontend/packages/core/src/appApi/EntityViewPageBuilder.tsx b/frontend/packages/core/src/appApi/EntityViewPageBuilder.tsx
new file mode 100644
index 0000000000..b323cd9504
--- /dev/null
+++ b/frontend/packages/core/src/appApi/EntityViewPageBuilder.tsx
@@ -0,0 +1,124 @@
+import React, { ComponentType, FC } from 'react';
+import { AppComponentBuilder, App } from './types';
+import { useEntity, useEntityUri, useEntityConfig } from './EntityContext';
+import { Route, Redirect, Switch } from 'react-router-dom';
+import List from '@material-ui/core/List';
+import ListItem from '@material-ui/core/ListItem';
+import EntityLink from './EntityLink';
+
+const EntityLayout: FC<{}> = ({ children }) => {
+  const config = useEntityConfig();
+  return (
+    <div style={{ backgroundColor: config.color.primary }}>{children}</div>
+  );
+};
+
+const EntitySidebar: FC<{}> = ({ children }) => {
+  return <List>{children}</List>;
+};
+
+const EntitySidebarItem: FC<{ title: string; path: string }> = ({
+  title,
+  path,
+}) => {
+  const entityUri = useEntityUri();
+
+  return (
+    <ListItem>
+      <EntityLink uri={entityUri} subPath={path}>
+        {title}
+      </EntityLink>
+    </ListItem>
+  );
+};
+
+type EntityViewPage = {
+  title: string;
+  path: string;
+  component: ComponentType<any>;
+};
+
+type Props = {
+  pages: EntityViewPage[];
+};
+
+const EntityViewComponent: FC<Props> = ({ pages }) => {
+  const { kind, id } = useEntity();
+  const basePath = `/entity/${kind}/${id}`;
+
+  return (
+    <EntityLayout>
+      <EntitySidebar>
+        {pages.map(({ title, path }) => (
+          <EntitySidebarItem key={path} title={title} path={path} />
+        ))}
+      </EntitySidebar>
+      <Switch>
+        {pages.map(({ path, component }) => (
+          <Route
+            key={path}
+            exact
+            path={`${basePath}/${path}`}
+            component={component}
+          />
+        ))}
+        <Redirect from={basePath} to={`${basePath}/${pages[0].path}`} />
+      </Switch>
+    </EntityLayout>
+  );
+};
+
+type EntityViewRegistration =
+  | {
+      type: 'page';
+      title: string;
+      path: string;
+      page: AppComponentBuilder;
+    }
+  | {
+      type: 'component';
+      title: string;
+      path: string;
+      component: ComponentType<any>;
+    };
+
+export default class EntityViewBuilder extends AppComponentBuilder {
+  private readonly registrations = new Array<EntityViewRegistration>();
+
+  addPage(
+    title: string,
+    path: string,
+    page: AppComponentBuilder,
+  ): EntityViewBuilder {
+    this.registrations.push({ type: 'page', title, path, page });
+    return this;
+  }
+
+  addComponent(
+    title: string,
+    path: string,
+    component: ComponentType<any>,
+  ): EntityViewBuilder {
+    this.registrations.push({ type: 'component', title, path, component });
+    return this;
+  }
+
+  build(app: App): ComponentType<any> {
+    const pages = this.registrations.map(registration => {
+      switch (registration.type) {
+        case 'page': {
+          const { title, path, page } = registration;
+          return { title, path, component: page.build(app) };
+        }
+        case 'component': {
+          const { title, path, component } = registration;
+          return { title, path, component };
+        }
+        default:
+          throw new Error(`Unknown EntityViewBuilder registration`);
+      }
+    });
+
+    return () => <EntityViewComponent pages={pages} />;
+  }
+}
diff --git a/frontend/packages/core/src/appApi/OverviewPageBuilder.tsx b/frontend/packages/core/src/appApi/OverviewPageBuilder.tsx
new file mode 100644
index 0000000000..67a0138436
--- /dev/null
+++ b/frontend/packages/core/src/appApi/OverviewPageBuilder.tsx
@@ -0,0 +1,50 @@
+import React, { ComponentType, FC } from 'react';
+import { App, AppComponentBuilder } from './types';
+
+type Props = {
+  app: App;
+  cards: ComponentType<any>[];
+};
+
+const OverviewPageComponent: FC<Props> = ({ cards }) => {
+  return (
+    <div>
+      {cards.map(CardComponent => (
+        <CardComponent />
+      ))}
+    </div>
+  );
+};
+
+type OverviewPageRegistration = {
+  type: 'component';
+  component: ComponentType<any>;
+};
+
+export default class OverviewPageBuilder extends AppComponentBuilder {
+  private readonly registrations = new Array<OverviewPageRegistration>();
+  private output?: ComponentType<any>;
+
+  addComponent(component: ComponentType<any>): OverviewPageBuilder {
+    this.registrations.push({ type: 'component', component });
+    return this;
+  }
+
+  build(app: App): ComponentType<any> {
+    if (this.output) {
+      return this.output;
+    }
+
+    const cards = this.registrations.map(reg => {
+      switch (reg.type) {
+        case 'component':
+          return reg.component;
+        default:
+          throw new Error(`Unknown OverviewPageBuilder registration`);
+      }
+    });
+
+    this.output = () => <OverviewPageComponent app={app} cards={cards} />;
+    return this.output;
+  }
+}
diff --git a/frontend/packages/core/src/appApi/api.ts b/frontend/packages/core/src/appApi/api.ts
new file mode 100644
index 0000000000..4d657ee606
--- /dev/null
+++ b/frontend/packages/core/src/appApi/api.ts
@@ -0,0 +1,21 @@
+import AppBuilder from './AppBuilder';
+import { EntityConfig } from './types';
+import EntityKind from './EntityKind';
+import OverviewPageBuilder from './OverviewPageBuilder';
+import EntityViewBuilder from './EntityViewPageBuilder';
+
+export function createApp() {
+  return new AppBuilder();
+}
+
+export function createEntityKind(config: EntityConfig) {
+  return new EntityKind(config);
+}
+
+export function createOverviewPage() {
+  return new OverviewPageBuilder();
+}
+
+export function createEntityView() {
+  return new EntityViewBuilder();
+}
diff --git a/frontend/packages/core/src/appApi/index.ts b/frontend/packages/core/src/appApi/index.ts
new file mode 100644
index 0000000000..d198cb66e4
--- /dev/null
+++ b/frontend/packages/core/src/appApi/index.ts
@@ -0,0 +1,5 @@
+export * from './types';
+export * from './api';
+export { useApp } from './AppContext';
+export { useEntity, useEntityConfig, useEntityUri } from './EntityContext';
+export { default as EntityLink } from './EntityLink';
diff --git a/frontend/packages/core/src/appApi/types.ts b/frontend/packages/core/src/appApi/types.ts
new file mode 100644
index 0000000000..f37848aca0
--- /dev/null
+++ b/frontend/packages/core/src/appApi/types.ts
@@ -0,0 +1,36 @@
+import { ComponentType } from 'react';
+
+export type EntityConfig = {
+  kind: string;
+  title: string;
+  icon: React.ComponentType<{ fontSize: number }>;
+  color: {
+    primary: string;
+    secondary: string;
+  };
+  pages: {
+    list?: ComponentType<{}> | AppComponentBuilder;
+    view?: ComponentType<{}> | AppComponentBuilder;
+  };
+};
+
+export type App = {
+  getEntityConfig(kind: string): EntityConfig;
+};
+
+export class AppComponentBuilder<T = any> {
+  build(_app: App): ComponentType<T> {
+    throw new Error('Must override build() in AppComponentBuilder');
+  }
+}
+
+export type User = {
+  id: string;
+  email: string;
+};
+
+export type UserApi = {
+  isLoggedIn(): Promise<boolean>;
+
+  getUser(): Promise<User>;
+};
diff --git a/frontend/packages/core/src/index.ts b/frontend/packages/core/src/index.ts
index 353b29ff72..45110734fb 100644
--- a/frontend/packages/core/src/index.ts
+++ b/frontend/packages/core/src/index.ts
@@ -1,3 +1,4 @@
+export * from './appApi';
 export * from './types';
 export { default as createPlugin } from './createPlugin';
 export { default as Page } from '../src/layout/Page';