const util = require("util");

module.exports = {};

module.exports.debug = true;

{
	let id = 0;
	function uniqid() {
		return id++;
	}
}
module.exports.uniqid = uniqid;

function lineReader(conn, lineCb) {
	let buffer = "";
	conn.on("data", (data) => {
		buffer += data.toString();
		let idx = buffer.indexOf("\n");
		while (idx != -1) {
			lineCb(buffer.slice(0, idx));
			buffer = buffer.slice(idx + 1);
			idx = buffer.indexOf("\n");
		}
	});
}
module.exports.lineReader = lineReader;

class Message {
	constructor(/*...*/) {
		if (typeof arguments[0] == "number") this.makeReply(...arguments);
		else this.makeCommand(...arguments);
	}

	makeCommand(method, ...args) {
		this.isCommand = true;
		this.method = method;
		this.args = args;
		this.id = uniqid();
	}

	makeReply(id, res, err) {
		this.isCommand = false;
		this.id = id;
		this.res = res;
		this.err = err;
	}

	toJSON() {
		if (this.isCommand) {
			return JSON.stringify({
				method: this.method,
				args: this.args, 
				id: this.id,
			});
		} else {
			return JSON.stringify({
				res: this.res,
				err: this.err, 
				id: this.id,
			});
		}
	}
}
module.exports.Message = Message;

class Connection {
	constructor(conn, msgCb) {
		this.conn = conn;
		lineReader(conn, (line) => {
			console.log("Received line '" + line + "'");
			let obj;
			try {
				obj = JSON.parse(line);
			} catch (e) {
				if (module.exports.debug) console.log("Invalid JSON received: " + line);
				return;
			}
			if (obj.method) {
				msgCb(new Message(obj.method, ...obj.args));
			} else {
				const msg = new Message(obj.id, obj.res, obj.err);
				if (this.replyHandlers[msg.id]) {
					this.replyHandlers[msg.id](msg);
					this.replyHandlers[msg.id] = null;
				} else {
					if (module.exports.debug) console.log("Reply for unexpected message id " + msg.id);
				}
			}
		});

		this.replyHandlers = {};

		// Send a ping once in a while
		this.pingInterval = setInterval(async () => {
			const msg = await this.send(new Message("ping"));
			if (module.exports.debug) console.log("Ping reply: " + util.inspect(msg));
		}, 600000);
	}

	send(msg) {
		const data = msg.toJSON();
		if (module.exports.debug) console.log("Writing to conn: " + data);
		this.conn.write(data + "\n");
		return new Promise((resolve, reject) => {
			this.replyHandlers[msg.id] = resolve;
		});
	}

	end() {
		clearInterval(this.pingInterval);
		this.conn.end();
	}
}
module.exports.Connection = Connection;