fp/packages/scout/src/imap.js

import { ImapFlow } from 'imapflow';
import EventEmitter from 'node:events';
import 'dotenv/config';
import { simpleParser } from 'mailparser';

// pinned to v2.0.1 due to https://github.com/jhurliman/node-rate-limiter/issues/80
import * as $limiter from 'limiter';
const { RateLimiter } = $limiter



if (!process.env.SCOUT_IMAP_SERVER) throw new Error('SCOUT_IMAP_SERVER is missing from env');
if (!process.env.SCOUT_IMAP_PORT) throw new Error('SCOUT_IMAP_PORT is missing from env');
if (!process.env.SCOUT_IMAP_USERNAME) throw new Error('SCOUT_IMAP_USERNAME is missing from env');
if (!process.env.SCOUT_IMAP_PASSWORD) throw new Error('SCOUT_IMAP_PASSWORD is missing from env');

const limiter = new RateLimiter({ tokensPerInterval: 1, interval: 3000 });

// https://stackoverflow.com/a/49428486/1004931
function streamToString(stream) {
    const chunks = [];
    return new Promise((resolve, reject) => {
        stream.on('data', (chunk) => chunks.push(Buffer.from(chunk)));
        stream.on('error', (err) => reject(err));
        stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
    })
}


export class Email extends EventEmitter {


    constructor() {
        super()
        this.client = null
    }

    async archiveMessage(uid) {
        await limiter.removeTokens(1);
        await this.client.messageDelete(uid, { uid: true })
    }

    async connect() {
        this.client = new ImapFlow({
            host: process.env.SCOUT_IMAP_SERVER,
            port: process.env.SCOUT_IMAP_PORT,
            secure: true,
            auth: {
                user: process.env.SCOUT_IMAP_USERNAME,
                pass: process.env.SCOUT_IMAP_PASSWORD
            }
        });

        this.registerEventListeners()
        await this.client.connect()
        const stat = await this.getStatus()
        if (stat.messages > 0) {
            await this.emitAllMessages()
        }
    }

    async reconnect() {
        console.log('    RECONNECTING...')
        delete this.client
        await this.connect()
    }

    async getStatus() {
        let lock = await this.client.getMailboxLock('INBOX');
        let status;
        try {
            status = await this.client.status('INBOX', { messages: true });
        } finally {
            lock.release()
        }
        return status
    }

    async loadMessage(uid) {
        console.log(`    💾 loading message uid=${uid}`)
        let lock = await this.client.getMailboxLock('INBOX');
        let dl, body
        try {
            dl = await this.client.download(uid, undefined, { uid: true })
            body = await streamToString(dl.content)
        } finally {
            lock.release()
        }
        return body
    }

    async emitAllMessages() {
        console.log('emitAllMessages is running')
        let lock = await this.client.getMailboxLock('INBOX');
        try {
            for await (let message of this.client.fetch('1:*', { envelope: true })) {
                // it is tempting to call this.client.download here, but that is not possible while the mailbox is locked.
                // client.download must be called outside of this lock
                // console.log('here is a message')
                console.log(JSON.stringify(message, null, 2))
                this.emit('message', message)
            }
        } finally {
            lock.release();
        }
    }

    registerEventListeners() {
        console.log(`    > REGISTERING EVENT LISTENERS <`)
        this.client.once('end', () => this.reconnect())
        this.client.on('exists', (evt) => {
            // console.log(`exists event! count=${evt.count} prevCount=${evt.prevCount}`)
            // console.log(evt)
            if (evt.path === 'INBOX') {
                this.emitAllMessages()
            }
        })
    }

}






// // Select and lock a mailbox. Throws if mailbox does not exist
// console.log('get lock')


// // log out and close connection
// // await client.logout();