/**
 * Implementation of the RakNet ping/pong protocol.
 * @see https://wiki.vg/Raknet_Protocol
 */

'use strict';

import dgram from 'dgram';

const MAGIC = "00ffff00fefefefefdfdfdfd12345678";
const START_TIME = new Date().getTime();

/**
 * Creates an Unconnected Ping packet.
 * @param {number} pingId
 * @returns {Buffer}
 * @see {@link https://wiki.vg/Raknet_Protocol#Unconnected_Ping}
 */
const createUnconnectedPingFrame = (pingId) => {
    const buffer = Buffer.alloc(33);
    buffer.writeUInt8(0x01, 0);
    buffer.writeBigInt64LE(BigInt(pingId), 1);
    Buffer.from(MAGIC, "hex").copy(buffer, 9);
    buffer.writeBigInt64LE(BigInt(0), 25);
    return buffer;
};

/**
 * Extract Modt from Unconnected Pong Packet and convert to an object
 * @param {Buffer} unconnectedPongPacket
 * @returns {Object}
 * @see {@link https://wiki.vg/Raknet_Protocol#Unconnected_Pong}
 */
const extractModt = (unconnectedPongPacket) => {
    // Skip everything to Modt
    const offset = 33;
    const length = unconnectedPongPacket.readUInt16BE(offset);
    let modt = unconnectedPongPacket.toString("utf-8", offset + 2, offset + 2 + length);

    const components = modt.split(';');
    const parsedComponents = {
        edition: components[0],
        name: components[1],
        version: {
            protocolVersion: Number(components[2]),
            minecraftVersion: components[3],
        },
        players: {
            online: Number(components[4]),
            max: Number(components[5])
        },
        serverId: components[6],
        mapName: components[7],
        gameMode: components[8]
    };

    return parsedComponents;
};

/**
 * Sends a ping request to the specified host and port.
 * @param {string} host - The IP address or hostname of the server.
 * @param {number} [port=19132] - The port number.
 * @param {function} cb - The callback function to handle the response.
 * @param {number} [timeout=5000] - The timeout duration in milliseconds.
 */
const ping = (host, port = 19132, cb, timeout = 5000) => {
    const socket = dgram.createSocket('udp4');

    // Set manual timeout interval.
    // This ensures the connection will NEVER hang regardless of internal state
    const timeoutTask = setTimeout(() => {
        socket.emit('error', new Error('Socket timeout'));
    }, timeout);

    const closeSocket = () => {
        socket.close();
        clearTimeout(timeoutTask);
    };

    // Generic error handler
    // This protects multiple error callbacks given the complex socket state
    // This is mostly dangerous since it can swallow errors
    let didFireError = false;

    /**
     * Handle any error that occurs during the ping process.
     * @param {Error} err The error that occurred.
     */
    const handleError = (err) => {
        closeSocket();

        if (!didFireError) {
            didFireError = true;
            cb(null, err);
        }
    };

    try {
        const ping = createUnconnectedPingFrame(new Date().getTime() - START_TIME);
        socket.send(ping, 0, ping.length, port, host);
    } catch (err) {
        handleError(err);
    }

    socket.on('message', (pongPacket) => {
        const id = pongPacket[0];

        switch (id) {
            case 0x1c: {
                const modtObject = extractModt(pongPacket);
                closeSocket();
                cb(modtObject, null);
                break;
            }

            default: {
                handleError(new Error('Received unexpected packet'));
                break;
            }
        }
    });

    socket.on('error', handleError);
};

/**
 * Asynchronously ping Minecraft Bedrock server.
 * The optional `options` argument can be an object with a `ping` (default is `19132`) or/and `timeout` (default is `5000`) property.
 * @param {string} host The Bedrock server address.
 * @param {import('../types/index.js').PingOptions} options The configuration for pinging Minecraft Bedrock server.
 * @returns {Promise<import('../types/index.js').BedrockPingResponse>}
 */
export const pingBedrock = (host, options = {}) => {
    if (!host) throw new Error('Host argument is not provided');

    const { port = 19132, timeout = 5000 } = options;

    return new Promise((resolve, reject) => {
        ping(host, port, (res, err) => {
            err ? reject(err) : resolve(res);
        }, timeout);
    });
};