Reject/throw as appropriate in ES6 exported methods if window.fdc3 is…

… not available

src/api/methods.ts

@@ -7,70 +7,91 @@ import {
   Listener,
 } from '..';
 
+const unavailableError = new Error(
+  'FDC3 DesktopAgent not available at `window.fdc3`.'
+);
+
+const rejectIfNoGlobal = (f: () => Promise<any>) => {
+  return window.fdc3 ? f() : Promise.reject(unavailableError);
+};
+
+const throwIfNoGlobal = (f: () => any) => {
+  if (!window.fdc3) {
+    throw unavailableError;
+  }
+  return f();
+};
+
 export const open: (name: string, context?: Context) => Promise<void> = (
   name,
   context
 ) => {
-  return window.fdc3.open(name, context);
+  return rejectIfNoGlobal(() => window.fdc3.open(name, context));
 };
 
 export const findIntent: (
   intent: string,
   context?: Context
 ) => Promise<AppIntent> = (intent, context) => {
-  return window.fdc3.findIntent(intent, context);
+  return rejectIfNoGlobal(() => window.fdc3.findIntent(intent, context));
 };
 
 export const findIntentsByContext: (
   context: Context
 ) => Promise<Array<AppIntent>> = context => {
-  return window.fdc3.findIntentsByContext(context);
+  return rejectIfNoGlobal(() => window.fdc3.findIntentsByContext(context));
 };
 
 export const broadcast: (context: Context) => void = context => {
-  window.fdc3.broadcast(context);
+  throwIfNoGlobal(() => window.fdc3.broadcast(context));
 };
 
 export const raiseIntent: (
   intent: string,
   context: Context,
   target?: string
 ) => Promise<IntentResolution> = (intent, context, target) => {
-  return window.fdc3.raiseIntent(intent, context, target);
+  return rejectIfNoGlobal(() =>
+    window.fdc3.raiseIntent(intent, context, target)
+  );
 };
 
 export const addIntentListener: (
   intent: string,
   handler: ContextHandler
 ) => Listener = (intent, handler) => {
-  return window.fdc3.addIntentListener(intent, handler);
+  return throwIfNoGlobal(() => window.fdc3.addIntentListener(intent, handler));
 };
 
 export const addContextListener: (
   contextTypeOrHandler: string | ContextHandler,
   handler?: ContextHandler
 ) => Listener = (a, b) => {
   if (typeof a !== 'function') {
-    return window.fdc3.addContextListener(a as string, b as ContextHandler);
+    return throwIfNoGlobal(() =>
+      window.fdc3.addContextListener(a as string, b as ContextHandler)
+    );
   } else {
-    return window.fdc3.addContextListener(a as ContextHandler);
+    return throwIfNoGlobal(() =>
+      window.fdc3.addContextListener(a as ContextHandler)
+    );
   }
 };
 
 export const getSystemChannels: () => Promise<Array<Channel>> = () => {
-  return window.fdc3.getSystemChannels();
+  return rejectIfNoGlobal(() => window.fdc3.getSystemChannels());
 };
 
 export const joinChannel: (channelId: string) => Promise<void> = channelId => {
-  return window.fdc3.joinChannel(channelId);
+  return rejectIfNoGlobal(() => window.fdc3.joinChannel(channelId));
 };
 
 export const getOrCreateChannel: (
   channelId: string
 ) => Promise<Channel> = channelId => {
-  return window.fdc3.getOrCreateChannel(channelId);
+  return rejectIfNoGlobal(() => window.fdc3.getOrCreateChannel(channelId));
 };
 
 export const getCurrentChannel: () => Promise<Channel> = () => {
-  return window.fdc3.getCurrentChannel();
+  return rejectIfNoGlobal(() => window.fdc3.getCurrentChannel());
 };