hippofish/packages/backend/src/misc/get-ip-hash.ts

import IPCIDR from "ip-cidr";

export function getIpHash(ip: string) {
	try {
		// because a single person may control many IPv6 addresses,
		// only a /64 subnet prefix of any IP will be taken into account.
		// (this means for IPv4 the entire address is used)
		const prefix = IPCIDR.createAddress(ip).mask(64);
		return `ip-${BigInt(`0b${prefix}`).toString(36)}`;
	} catch (e) {
		const prefix = IPCIDR.createAddress(ip.replace(/:[0-9]+$/, "")).mask(64);
		return `ip-${BigInt(`0b${prefix}`).toString(36)}`;
	}
}