pop3-to-imap/imap/logic.js

class IMAPController {
	constructor (socket, tag) {
		this.socket = socket;
		this.tag = tag;
	}
	
	out (answer) {
		console.debug("IMAP response:", answer);
		this.socket.write(`${this.tag} ${answer}`);
	}
	
	untaggedOut (answer) {
		console.debug("IMAP response:", answer);
		this.socket.write(answer);
	}
	
	close () {
		this.socket.end();
	}
}

const messages = [
	{
		id: 1,
		uid: 101,
		flags: ["\\Seen"],
		raw: `From: Example <ex@example.com>\r\nTo: You <you@example.com>\r\nSubject: Hello\r\n\r\nThis is a test email.`
	}
];
const parseUidRange = (input) => {
	if (input === '*') return messages.map(msg => msg.uid);
	if (input.includes(':')) {
		const [start, end] = input.split(':').map(Number);
		return messages
			.map(msg => msg.uid)
			.filter(uid => uid >= start && uid <= (isNaN(end) ? Infinity : end));
	}
	return [Number(input)];
};

class Commands {
	constructor (client) {
		this.client = client;
	}
	
	// Methods
	// Required commands
	
	async capability (args, controller) {
		/*if (args.length > 0)
			return out();*/
		controller.untaggedOut("* CAPABILITY IMAP4rev1 IDLE\r\n");
		controller.out("OK CAPABILITY completed\r\n");
	}
	
	async logout (args, controller) {
		controller.untaggedOut("* BYE Logging out\r\n");
		controller.out("OK LOGOUT completed\r\n");
		
		controller.close();
	}
	
	async noop(args, controller) {
		controller.out("OK NOOP completed\r\n");
	}

	async login(args, controller) {
		//this.client.state = "authenticated";
		controller.out("OK LOGIN completed\r\n");
	}

	// Mailposts

	async list(args, controller) {
		controller.untaggedOut(`* LIST (\\HasNoChildren) "." "INBOX"\r\n`);
		controller.out("OK LIST completed\r\n");
	}

	async select(args, controller) {
		const messageCount = messages.length;

		controller.untaggedOut("* FLAGS (\\Seen \\Answered \\Flagged \\Deleted \\Draft)\r\n");
		controller.untaggedOut(`* ${messageCount} EXISTS\r\n`);
		controller.untaggedOut(`* ${messageCount} RECENT\r\n`);
		controller.untaggedOut("* OK [UNSEEN 1] First unseen\r\n");
		controller.untaggedOut("* OK [UIDVALIDITY 1] UIDs valid\r\n");
		controller.untaggedOut(`* OK [UIDNEXT ${messageCount + 1}] Predicted next UID\r\n`);
		controller.out("OK [READ-WRITE] SELECT completed\r\n");

		//this.client.state = "selected";
	}

	// Mailpost's messages

	async fetch(args, controller) {
		if (!args || args.length < 2) {
			return controller.out("BAD FETCH requires message sequence and data item\r\n");
		}

		const seq = args[0];
		const item = args.slice(1).join(" ").toUpperCase();

		if (seq !== "1") {
			return controller.out("NO FETCH only supports message 1 for now\r\n");
		}

		if (!item.includes("BODY[]")) {
			return controller.out("NO FETCH only supports BODY[] for now\r\n");
		}

		const msg = messages.find(m => m.id === 1);
		if (!msg) {
			return controller.out("NO Message not found\r\n");
		}

		const body = msg.raw;
		controller.untaggedOut(`* 1 FETCH (BODY[] {${body.length}}\r\n${body}\r\n)\r\n`);
		controller.out("OK FETCH completed\r\n");
	}

	async uid(args, controller) {
		if (!args || args.length < 2) {
			return controller.out("BAD UID requires subcommand and arguments\r\n");
		}

		const subCommand = args[0].toUpperCase();

		if (subCommand === "FETCH") {
			const uidArg = args[1];
			const fetchFields = args.slice(2).join(" ").toUpperCase();

			const msg = messages.find(m => m.uid === Number(uidArg));
			if (!msg) {
				return controller.out("NO No such message\r\n");
			}

			const headersOnly = msg.raw.split("\r\n\r\n")[0] + "\r\n";
			const headerLength = headersOnly.length;
			const bodySize = msg.raw.length;
			const flags = msg.flags.join(" ");

			controller.untaggedOut(
				`* ${msg.id} FETCH (` +
				`UID ${msg.uid} ` +
				`RFC822.SIZE ${bodySize} ` +
				`FLAGS (${flags}) ` +
				`BODY[HEADER.FIELDS (From To Subject Date Message-ID)] {${headerLength}}\r\n` +
				headersOnly +
				")\r\n"
			);

			return controller.out("OK UID FETCH completed\r\n");
		}

		controller.out("BAD UID subcommand not supported\r\n");
	}

	async store(args, controller) {
		controller.out("OK STORE not yet implemented\r\n");
	}

	async expunge(args, controller) {
		controller.out("OK EXPUNGE not yet implemented\r\n");
	}

	async copy(args, controller) {
		controller.out("OK COPY not yet implemented\r\n");
	}

	async close(args, controller) {
		controller.out("OK CLOSE not yet implemented\r\n");
	}

	async search(args, controller) {
		controller.out("* SEARCH\r\n");
		controller.out("OK SEARCH completed\r\n");
	}

	async examine(args, controller) {
		controller.out("OK EXAMINE not yet implemented\r\n");
	}

	async append(args, controller) {
		controller.out("OK APPEND not yet implemented\r\n");
	}

	// Push-notifications (IDLE)

	async idle(args, controller) {
		controller.untaggedOut("+ idling\r\n");
		controller.out("OK IDLE not yet implemented\r\n");
	}
}

class Client {
	constructor (socket) {
		this.socket = socket;
		this.commands = new Commands(this);
	}
	
	command (tag, command, args) {
		//console.debug("this >>", this, this.socket, this.commands);
		const cmd = this.commands[command.toLowerCase()];
		if (cmd === undefined) {
			return this.socket.write(`${tag} BAD unknown command\r\n`);
		}
		cmd.call(this.commands, args, new IMAPController(this.socket, tag));
	}
}

module.exports = { Client };