[codex] Handle webchat reconnect catch-up

__tests__/api/webchat/messages_test.js

@@ -0,0 +1,33 @@
+/**
+ * @jest-environment jsdom
+ */
+
+import WebchatMessagesAPI from '../../../src/api/webchat/messages'
+import Hellotext from '../../../src/hellotext'
+
+describe('WebchatMessagesAPI', () => {
+  beforeEach(() => {
+    Hellotext.business = { id: 'business-id' }
+    jest.spyOn(Hellotext, 'session', 'get').mockReturnValue('session-123')
+
+    global.fetch = jest.fn().mockResolvedValue({
+      json: jest.fn().mockResolvedValue({ messages: [] }),
+    })
+  })
+
+  afterEach(() => {
+    jest.restoreAllMocks()
+  })
+
+  it('requests catch-up messages after the supplied message id', async () => {
+    const api = new WebchatMessagesAPI('webchat-id')
+
+    await api.catchUp('message-123')
+
+    const url = new URL(global.fetch.mock.calls[0][0])
+
+    expect(url.pathname).toBe('/v1/public/webchats/webchat-id/messages')
+    expect(url.searchParams.get('after_id')).toBe('message-123')
+    expect(url.searchParams.get('session')).toBe('session-123')
+  })
+})