Communication

discendo-sdk/communication handles section-wide announcements, threaded discussions, and routes SDK domain events to external notification dispatchers.

::: important The First Rule of Communication The SDK never sends emails, push notifications, or SMS. That is your application's job. The SDK structures the data, enforces audience segregation, and emits typed events for your notification dispatchers to handle. :::

---

At a Glance

Import	import { CommunicationService, bridgeEventBusToNotificationSink } from 'discendo-sdk/communication'
Repositories	AnnouncementRepository, ThreadRepository
Seams	NotificationSink
Events	communication.deliveryFailed
Permissions	communication.postAnnouncement, communication.postGuardianAnnouncement, communication.viewAnnouncements, communication.viewGuardianAnnouncements, communication.participate
Enforcement	Opt-in via constructor options { enforcement: { policy, repos } }

---

Data Models

type AnnouncementAudience = "students" | "guardians";

interface Announcement {
  id: string;
  sectionId: string;
  title: string;
  body: string;
  postedAt: Date;
  audience?: AnnouncementAudience; // Default: 'students'
}

interface ThreadPost {
  id: string;
  authorId: string;
  body: string;
  postedAt: Date;
}

interface Thread {
  id: string;
  contentId?: string; // Optionally tied to a specific assignment/lesson
  sectionId: string;
  title: string;
  posts: ThreadPost[];
}

---

CommunicationService

new CommunicationService(
  announcements: AnnouncementRepository,
  threads: ThreadRepository,
  sink?: NotificationSink,
  options?: {
    enforcement?: { policy: PermissionPolicy; repos: RepositoryContext }
    onDeliveryError?: (err: unknown, announcement: Announcement) => void
  }
)

Announcements

// 1. Post student announcement
await commsService.postAnnouncement(
  {
    sectionId: "sec-101",
    title: "Midterm Room Assigned",
    body: "The exam will take place in Auditorium B.",
    audience: "students",
  },
  { actorId: "u-instructor" },
);

// 2. Post guardian-only announcement (e.g. for parents)
await commsService.postAnnouncement(
  {
    sectionId: "sec-101",
    title: "Field Trip Permission Forms",
    body: "Please sign and return the forms by Friday.",
    audience: "guardians",
  },
  { actorId: "u-instructor" },
);

• Audience Segregation: Students cannot read guardian announcements; guardians cannot read student announcements.
• Permissions: Posting student announcements requires communication.postAnnouncement (instructors, delegable to TAs). Posting guardian announcements requires communication.postGuardianAnnouncement (instructors only).

Discussion Threads

// Create discussion thread on an assignment
const thread = await commsService.createThread(
  {
    sectionId: "sec-101",
    contentId: "assign-lab1",
    title: "Question regarding Question 3",
  },
  { actorId: "u-student" },
);

// Post a reply
await commsService.reply(
  thread.id,
  "Remember to normalize your units before calculating velocity.",
  { actorId: "u-ta" },
);

Requires communication.participate (students, TAs, instructors).

---

Bridging Events to Notifications

discendo-sdk/communication includes a built-in bridge that maps domain events from the EventBus into notification payloads:

import { bridgeEventBusToNotificationSink } from "discendo-sdk/communication";

// Define your delivery sink (e.g. SendGrid, Firebase, Novu)
const myNotificationSink: NotificationSink = {
  dispatch: async (event) => {
    switch (event.type) {
      case "gradePosted":
        await emailClient.sendGradeAlert(event.userId, event.score);
        break;
      case "announcementCreated":
        await pushClient.broadcastToSection(event.sectionId, event.title);
        break;
    }
  },
};

// Connect the bridge to your EventBus
bridgeEventBusToNotificationSink(bus, myNotificationSink, {
  resolveContentId: async (submissionId) => {
    const sub = await db.submissions.findById(submissionId);
    return sub?.contentId ?? null;
  },
});

---

Known Limitations

• No rich-text sanitize engine: Markdown/HTML sanitization of announcement bodies must be performed by your application API before passing strings to the SDK.
• No thread nesting: Discussion threads support flat reply lists under a thread root; multi-level nested commentary trees are not natively modeled.