Messenger/packages/backend/src/modules/conversations/conversations.service.ts

import type {
  Conversation,
  ConversationMember,
  ConversationNewEvent,
  ConversationMembershipEvent,
  ReadReceiptEvent,
} from '@altricade/core';
import { userChannel, EventType } from '@altricade/core';
import { HttpError } from '../../shared/http-error';
import type { Publisher } from '../../shared/publisher';
import { toPublicUser } from '../users';
import type { UsersRepository } from '../users';
import type { ConversationsRepository, DeliveryInfo } from './conversations.repository';
import type { ReadStateRepository } from './read-state.repository';
import type { Deliver } from './delivery';
import { toConversation, toMember, memberToPublicUser } from './conversations.mapper';

export interface ConversationsServiceDeps {
  conversations: ConversationsRepository;
  users: UsersRepository;
  readState: ReadStateRepository;
  deliver: Deliver;
  publish: Publisher;
}

export interface ConversationsService {
  createDirect(actorId: string, username: string): Promise<Conversation>;
  createGroup(actorId: string, title: string, memberUsernames: string[]): Promise<Conversation>;
  list(userId: string): Promise<Conversation[]>;
  get(conversationId: string, userId: string): Promise<Conversation>;
  listMembers(conversationId: string, userId: string): Promise<ConversationMember[]>;
  addMember(conversationId: string, actorId: string, username: string): Promise<ConversationMember[]>;
  removeMember(conversationId: string, actorId: string, targetUserId: string): Promise<void>;
  isMember(conversationId: string, userId: string): Promise<boolean>;
  getDeliveryInfo(conversationId: string): Promise<DeliveryInfo | undefined>;
  markRead(conversationId: string, userId: string, seq: number): Promise<void>;
}

export const createConversationsService = (
  deps: ConversationsServiceDeps,
): ConversationsService => {
  const { conversations, users, readState, deliver, publish } = deps;

  const assertMember = async (conversationId: string, userId: string): Promise<void> => {
    if (!(await conversations.isMember(conversationId, userId))) {
      throw new HttpError(403, 'not_a_member', 'You are not a member of this conversation');
    }
  };

  const assertOwner = async (conversationId: string, userId: string): Promise<void> => {
    if ((await conversations.getRole(conversationId, userId)) !== 'owner') {
      throw new HttpError(403, 'not_owner', 'Only the group owner can do this');
    }
  };

  const conversationNew = (conversation: Conversation): ConversationNewEvent => ({
    type: EventType.ConversationNew,
    conversation,
  });

  const membership = (
    action: ConversationMembershipEvent['action'],
    conversationId: string,
    userId: string,
  ): ConversationMembershipEvent => ({ type: EventType.ConversationMembership, action, conversationId, userId });

  return {
    createDirect: async (actorId, username) => {
      const target = await users.findByUsername(username);
      if (target === undefined) {
        throw new HttpError(404, 'user_not_found', 'No such user');
      }
      if (target.id === actorId) {
        throw new HttpError(400, 'invalid_target', 'Cannot start a direct chat with yourself');
      }
      const targetPublic = toPublicUser(target);
      const { conversation, created } = await conversations.findOrCreateDirect(actorId, target.id);

      if (created) {
        const actorRow = await users.findById(actorId);
        const actorPublic = actorRow === undefined ? null : toPublicUser(actorRow);
        await publish(
          userChannel(target.id),
          conversationNew(toConversation(conversation, actorPublic)),
        );
        await publish(
          userChannel(actorId),
          conversationNew(toConversation(conversation, targetPublic)),
        );
      }
      return toConversation(conversation, targetPublic);
    },

    createGroup: async (actorId, title, memberUsernames) => {
      const memberIds: string[] = [];
      for (const username of memberUsernames) {
        const found = await users.findByUsername(username);
        if (found !== undefined && found.id !== actorId) {
          memberIds.push(found.id);
        }
      }
      const conversation = toConversation(
        await conversations.createGroup(title, actorId, memberIds),
        null,
      );
      for (const userId of [actorId, ...memberIds]) {
        await publish(userChannel(userId), conversationNew(conversation));
      }
      return conversation;
    },

    list: async (userId) => {
      const rows = await conversations.listForUser(userId);
      const directIds = rows.filter((row) => row.type === 'direct').map((row) => row.id);
      const peers = await conversations.peersForDirect(userId, directIds);
      const unread = await readState.unreadCounts(userId);
      return rows.map((row) => {
        const count = unread.get(row.id) ?? 0;
        if (row.type !== 'direct') {
          return toConversation(row, null, count);
        }
        const peer = peers.get(row.id);
        return toConversation(row, peer === undefined ? null : memberToPublicUser(peer), count);
      });
    },

    get: async (conversationId, userId) => {
      await assertMember(conversationId, userId);
      const conversation = await conversations.findById(conversationId);
      if (conversation === undefined) {
        throw new HttpError(404, 'not_found', 'Conversation not found');
      }
      const count = await readState.unreadFor(conversationId, userId);
      if (conversation.type !== 'direct') {
        return toConversation(conversation, null, count);
      }
      const peer = await conversations.getPeer(conversationId, userId);
      return toConversation(
        conversation,
        peer === undefined ? null : memberToPublicUser(peer),
        count,
      );
    },

    listMembers: async (conversationId, userId) => {
      await assertMember(conversationId, userId);
      return (await conversations.listMembers(conversationId)).map(toMember);
    },

    addMember: async (conversationId, actorId, username) => {
      await assertOwner(conversationId, actorId);
      const target = await users.findByUsername(username);
      if (target === undefined) {
        throw new HttpError(404, 'user_not_found', 'No such user');
      }
      await conversations.addMember(conversationId, target.id, 'member');
      const conversation = await conversations.findById(conversationId);
      if (conversation !== undefined) {
        await publish(userChannel(target.id), conversationNew(toConversation(conversation, null)));
      }
      await publish(userChannel(target.id), membership('added', conversationId, target.id));
      return (await conversations.listMembers(conversationId)).map(toMember);
    },

    removeMember: async (conversationId, actorId, targetUserId) => {
      if (actorId !== targetUserId) {
        await assertOwner(conversationId, actorId);
      }
      await conversations.removeMember(conversationId, targetUserId);
      await publish(userChannel(targetUserId), membership('removed', conversationId, targetUserId));
    },

    isMember: (conversationId, userId) => conversations.isMember(conversationId, userId),

    getDeliveryInfo: (conversationId) => conversations.getDeliveryInfo(conversationId),

    markRead: async (conversationId, userId, seq) => {
      await assertMember(conversationId, userId);
      await readState.setRead(conversationId, userId, seq);
      const event: ReadReceiptEvent = { type: EventType.ReadReceipt, conversationId, userId, seq };
      await deliver(conversationId, event);
    },
  };
};

declare module 'fastify' {
  interface FastifyInstance {
    conversationsService: ConversationsService;
  }
}