somod-chat-service/build/serverless/functions/messageStreamHandler.js

Serverless Chat Service from SOMOD

import { threadCache } from "../../lib/threadCache";
import { putMessage } from "../../lib/message";
import { unmarshall } from "@aws-sdk/util-dynamodb";
import { PublishCommand, SNSClient } from "@aws-sdk/client-sns";
const sns = new SNSClient();
const transfer = async (message) => {
    if (message.action == "delete") {
        return;
    }
    const thread = await threadCache.get(message.threadId);
    if (thread) {
        const targets = thread.participants.filter(p => p != message.from);
        await Promise.all(targets.map(async (target) => {
            await putMessage(process.env.MESSAGE_BOX_TABLE_NAME + "", target, message);
        }));
    }
    else {
        throw new Error(`Thread '${message.threadId}' not found`);
    }
};
const notify = async (userId, message) => {
    const publishCommand = new PublishCommand({
        TopicArn: process.env.MSG_NOTIFICATION_TOPIC + "",
        Message: JSON.stringify(message),
        MessageAttributes: { userId: { DataType: "String", StringValue: userId } }
    });
    await sns.send(publishCommand);
};
const streamHandler = async (event) => {
    const messageRaw = event.Records[0]?.dynamodb?.NewImage;
    const eventName = event.Records[0]?.eventName ?? "";
    if (eventName == "REMOVE") {
        return;
    }
    if (messageRaw) {
        const message = unmarshall(messageRaw);
        const { userId, ...msg } = message;
        if (message.from === userId) {
            await transfer(msg);
        }
        else {
            await notify(userId, msg);
        }
    }
    else {
        // eslint-disable-next-line no-console
        console.error(event);
        throw new Error("messageRaw is not found in the event");
    }
};
export default streamHandler;