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

import IPCIDR from 'ip-cidr';

export function getIpHash(ip: string): 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);
	}
}