(core) Add new Grist login page

Summary:
Adds a new Grist login page to the login app, and replaces the
server-side Cognito Google Sign-In flow with Google's own OAuth flow.

Test Plan: Browser and server tests.

Reviewers: jarek

Reviewed By: jarek

Differential Revision: https://phab.getgrist.com/D3332

app/common/LoginState.ts

@@ -1,31 +0,0 @@
-import {parseSubdomain} from 'app/common/gristUrls';
-
-// This interface is used by the standalone login-connect tool for knowing where to redirect to,
-// by Client.ts to construct this info, and by CognitoClient to decide what to do.
-
-export interface LoginState {
-  // Locally-running Grist uses localPort, while hosted uses subdomain. Login-connect uses this to
-  // redirect back to the localhost or to the subdomain.
-  localPort?: number;
-  subdomain?: string;
-  baseDomain?: string;  // the domain with the (left-most) subdomain removed, e.g. ".getgrist.com".
-                        // undefined on localhost.
-
-  // Standalone version sets clientId, used later to find the LoginSession. Hosted and dev
-  // versions rely on the browser cookies instead, specifically on the session cookie.
-  clientId?: string;
-
-  // Hosted and dev versions set redirectUrl and redirect to it when login or logout completes.
-  // Standalone version omits redirectUrl, and serves a page which closes the window.
-  redirectUrl?: string;
-}
-
-/// Allowed localhost addresses.
-export const localhostRegex = /^localhost(?::(\d+))?$/i;
-
-export function getLoginState(reqHost: string): LoginState|null {
-  const {org, base} = parseSubdomain(reqHost);
-  const matchPort = localhostRegex.exec(reqHost);
-  return org ? {subdomain: org, baseDomain: base} :
-    matchPort ? {localPort: matchPort[1] ? parseInt(matchPort[1], 10) : 80} : null;
-}

app/common/gristUrls.ts

@@ -2,7 +2,6 @@ import {BillingPage, BillingSubPage, BillingTask} from 'app/common/BillingAPI';
 import {OpenDocMode} from 'app/common/DocListAPI';
 import {EngineCode} from 'app/common/DocumentSettings';
 import {encodeQueryParams, isAffirmative} from 'app/common/gutil';
-import {localhostRegex} from 'app/common/LoginState';
 import {LocalPlugin} from 'app/common/plugin';
 import {StringUnion} from 'app/common/StringUnion';
 import {UIRowId} from 'app/common/UIRowId';
@@ -34,7 +33,7 @@ export type WelcomePage = typeof WelcomePage.type;
 export const AccountPage = StringUnion('account');
 export type AccountPage = typeof AccountPage.type;
 
-export const LoginPage = StringUnion('signup', 'verified', 'forgot-password');
+export const LoginPage = StringUnion('signup', 'login', 'verified', 'forgot-password');
 export type LoginPage = typeof LoginPage.type;
 
 // Overall UI style.  "full" is normal, "light" is a single page focused, panels hidden experience.
@@ -89,7 +88,7 @@ export interface IGristUrlState {
     billingPlan?: string;
     billingTask?: BillingTask;
     embed?: boolean;
-    next?: string;
+    state?: string;
     style?: InterfaceStyle;
     compare?: string;
     linkParameters?: Record<string, string>;  // Parameters to pass as 'user.Link' in granular ACLs.
@@ -302,13 +301,16 @@ export function decodeUrl(gristConfig: Partial<GristLoadConfig>, location: Locat
 
   if (map.has('signup')) {
     state.login = 'signup';
+  } else if (map.has('login')) {
+    state.login = 'login';
   } else if (map.has('verified')) {
     state.login = 'verified';
   } else if (map.has('forgot-password')) {
     state.login = 'forgot-password';
   }
-
-  if (sp.has('next')) { state.params!.next = sp.get('next')!; }
+  if (sp.has('state')) {
+    state.params!.state = sp.get('state')!;
+  }
 
   if (sp.has('style')) {
     state.params!.style = InterfaceStyle.parse(sp.get('style'));
@@ -407,6 +409,9 @@ export function parseSubdomain(host: string|undefined): {org?: string, base?: st
   return {};
 }
 
+// Allowed localhost addresses.
+const localhostRegex = /^localhost(?::(\d+))?$/i;
+
 /**
  * Like parseSubdomain, but throws an error if neither of these cases apply:
  *   - host can be parsed into a valid subdomain and a valid base domain.
@@ -566,7 +571,7 @@ export function isOrgInPathOnly(host?: string): boolean {
     const gristConfig: GristLoadConfig = (window as any).gristConfig;
     return (gristConfig && gristConfig.pathOnly) || false;
   } else {
-    if (host && host.match(/^localhost(:[0-9]+)?$/)) { return true; }
+    if (host && host.match(localhostRegex)) { return true; }
     return (process.env.GRIST_ORG_IN_PATH === 'true');
   }
 }

app/common/gutil.ts

@@ -921,3 +921,12 @@ export function getDistinctValues<T>(values: readonly T[], count: number = Infin
   }
   return distinct;
 }
+
+/**
+ * Asserts that variable `name` has a non-nullish `value`.
+ */
+export function assertIsDefined<T>(name: string, value: T): asserts value is NonNullable<T> {
+  if (value === undefined || value === null) {
+    throw new Error(`Expected '${name}' to be defined, but received ${value}`);
+  }
+}