"use strict";

class IP {
    /**
     * 
     * @param {Number} fo First octet
     * @param {Number} se Second octet
     * @param {Number} to Third octet
     * @param {Number} lo Last octet
     */
    constructor(fo, se, to, lo) {
        this.raw = BigInt(fo) << 24n | BigInt(se) << 16n | BigInt(to) << 8n | BigInt(lo);
    }

    /**
     * 
     * @param {BigInt} num Amount to add
     */
    add(num=1n) {
        if (typeof(num) !== typeof(0n)) {
            num = BigInt(num);
        }
        this.raw += num;
    }

    /**
     * 
     * @param {BigInt} num Amount to sub
     */
    sub(num=1n) {
        if (typeof(num) !== typeof(0n)) {
            num = BigInt(num);
        }
        this.raw -= num;
    }

    /**
     * 
     * @param {Number} num Which octet to pull (0-based)
     */
    octet(num) {
        if (typeof(num) !== typeof(0n)) {
            num = BigInt(num);
        }
        if (num > 3n) throw new Error("Four octets in IPv4 IP-address");

        return this.raw >> (8n * (3n - num)) & 0xFFn;
    }

    toString() {
        return `${this.raw >> 24n & 0xFFn}.${this.raw >> 16n & 0xFFn}.${this.raw >> 8n & 0xFFn}.${this.raw & 0xFFn}`;
    }

    clone() {
        return new IP(this.octet(0n), this.octet(1n), this.octet(2n), this.octet(3n));
    }
}

class Subnet {
    /**
     * 
     * @param {IP} ip 
     * @param {Number} subnetMask 
     */
    constructor(ip, subnetMask) {
        this.subnetCapacity = Math.pow(2, 32 - subnetMask);
        this.gateway = ip;

        const bmask = "".padStart(32 - subnetMask, 0).padStart(32, 1);
        const fo = parseInt(bmask.substr(0, 8), 2);
        const se = parseInt(bmask.substr(8, 8), 2);
        const to = parseInt(bmask.substr(16, 8), 2);
        const lo = parseInt(bmask.substr(24, 8), 2);
        this.mask = new IP(fo, se, to, lo);

        this.firstIP = this.gateway.clone();
        this.firstIP.add(1);
        this.lastIP = this.firstIP.clone();
        this.lastIP.add(this.subnetCapacity);
        this.lastIP.sub(3);
        this.broadcastIP = this.lastIP.clone();
        this.broadcastIP.add(1);
    }
}