/*
    SMTP Proxy
    Author: Alex Rennie-Lis
    Description: Presents an unauthenticated SMTP server for local legacy devices, and 
        proxies traffic to a defined relay host
    Version: 1.0.0
*/

const SMTPServer = require("smtp-server").SMTPServer;
const nodemailer = require("nodemailer");

if (
    !process.env.RELAY_HOST || 
    !process.env.RELAY_PORT
) {
    console.log ("Missing configuration.");
    process.exit (1);
}

const transporter = nodemailer.createTransport({
    host: process.env.RELAY_HOST,
    port: parseInt(process.env.RELAY_PORT) || 465,
    secure: process.env.RELAY_PORT === "465",
    auth: {
        user: process.env.RELAY_USER,
        pass: process.env.RELAY_PASS
    },
    // VERBOSE DEBUGGING
    logger: false,
    debug: false 
});

// Verify the connection on startup
transporter.verify((error, success) => {
    if (error) {
        console.error("Transporter Config Error:", error);
    }
    else {
        console.log("Upstream relay is ready.");
    }
});

const server = new SMTPServer({
    authOptional: true,
    onData(stream, session, callback) {
        console.log ("Relaying message...");

        const envelope = {
            from: session.envelope.mailFrom.address,
            to: session.envelope.rcptTo.map(r => r.address)
        };
        
        transporter.sendMail ({envelope: envelope, raw: stream}, (err, info) => {
            if (err) {
                console.error ("Relay Error:", err.message);
                return callback (new Error ("Relay failed!"));
            }
            console.log("Relay success:", info.messageId);
            callback();
        });
    }
});

const listenPort = process.env.SMTP_PORT || 2525; // Default to port 2525

server.listen (listenPort, '0.0.0.0', () => {
    console.log (`Relay active: Port ${listenPort} -> ${process.env.RELAY_HOST}:${process.env.RELAY_PORT}`);
});