Add OpenID token request flow to WidgetApi

As per MSC1960.

src/widgets/WidgetApi.ts

@@ -65,6 +65,13 @@ export interface FromWidgetRequest extends WidgetRequest {
     response: any;
 }
 
+export interface OpenIDCredentials {
+    accessToken: string;
+    tokenType: string;
+    matrixServerName: string;
+    expiresIn: number;
+}
+
 /**
  * Handles Element <--> Widget interactions for embedded/standalone widgets.
  *
@@ -78,6 +85,8 @@ export class WidgetApi extends EventEmitter {
     private inFlightRequests: { [requestId: string]: (reply: FromWidgetRequest) => void } = {};
     private readyPromise: Promise<any>;
     private readyPromiseResolve: () => void;
+    private openIDCredentialsCallback: () => void;
+    public openIDCredentials: OpenIDCredentials;
 
     /**
      * Set this to true if your widget is expecting a ready message from the client. False otherwise (default).
@@ -121,6 +130,10 @@ export class WidgetApi extends EventEmitter {
                         // Acknowledge that we're shut down now
                         this.replyToRequest(<ToWidgetRequest>payload, {});
                     });
+                } else if (payload.action === KnownWidgetActions.ReceiveOpenIDCredentials) {
+                    // Save OpenID credentials
+                    this.setOpenIDCredentials(<ToWidgetRequest>payload);
+                    this.replyToRequest(<ToWidgetRequest>payload, {});
                 } else {
                     console.warn(`[WidgetAPI] Got unexpected action: ${payload.action}`);
                 }
@@ -135,6 +148,32 @@ export class WidgetApi extends EventEmitter {
         });
     }
 
+    public setOpenIDCredentials(value: WidgetRequest) {
+        const data = value.data;
+        if (data.state === 'allowed') {
+            this.openIDCredentials = {
+                accessToken: data.access_token,
+                tokenType: data.token_type,
+                matrixServerName: data.matrix_server_name,
+                expiresIn: data.expires_in,
+            }
+        } else if (data.state === 'blocked') {
+            this.openIDCredentials = null;
+        }
+        if (['allowed', 'blocked'].includes(data.state) && this.openIDCredentialsCallback) {
+            this.openIDCredentialsCallback()
+        }
+    }
+
+    public requestOpenIDCredentials(credentialsResponseCallback: () => void) {
+        this.openIDCredentialsCallback = credentialsResponseCallback;
+        this.callAction(
+            KnownWidgetActions.GetOpenIDCredentials,
+            {},
+            this.setOpenIDCredentials,
+        );
+    }
+
     public waitReady(): Promise<any> {
         return this.readyPromise;
     }