mirror of
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89 lines
3.6 KiB
TypeScript
89 lines
3.6 KiB
TypeScript
/*
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* Copyright (C) 2024-present Puter Technologies Inc.
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*
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* This file is part of Puter.
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*
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* Puter is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published
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* by the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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/**
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* Shape and minting of `user.referral_code`.
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*
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* A referral code is a public, shareable handle for one account, so the only
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* mechanism here is "what a code may look like" and "produce a fresh one". What
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* a redemption is worth, and when a pattern of redemptions is abuse, is decided
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* elsewhere.
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*
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* Codes have exactly ONE canonical form — upper case — and every boundary
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* normalizes to it before touching a database or a counter. Two reasons:
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*
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* - Collations disagree. MySQL's `latin1_swedish_ci` matches a code
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* case-insensitively, SQLite and Postgres do not, so `ab12cd34` resolving to
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* an account would depend on the engine.
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* - Anything that counts redemptions per code keys off the code string. Left
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* un-normalized, `AB12CD34` and `Ab12cd34` are one code to the lookup and two
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* to the counters, which is a free way around any per-code cap.
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*/
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import crypto from 'crypto';
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/** `user.referral_code` is `varchar(16)`; a longer value can't be stored. */
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export const REFERRAL_CODE_MAX_LENGTH = 16;
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/** Length of a newly minted code. 32^8 ≈ 1.1e12 possibilities. */
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export const REFERRAL_CODE_LENGTH = 8;
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/**
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* Accepted canonical shape. Deliberately wider than the mint alphabet below:
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* codes minted by earlier versions of the program drew from the full
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* alphanumeric set, and they must keep resolving.
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*/
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export const REFERRAL_CODE_SHAPE = new RegExp(
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`^[A-Z0-9]{4,${REFERRAL_CODE_MAX_LENGTH}}$`,
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);
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/**
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* Crockford base32 — the alphanumerics minus `I`, `L`, `O` and `U`. Dropping
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* the letters that read as digits keeps a code transcribable from a screen or
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* over the phone, and dropping `U` keeps most accidental profanity out of a
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* code users are asked to share.
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*/
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const MINT_ALPHABET = '0123456789ABCDEFGHJKMNPQRSTVWXYZ';
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/**
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* The canonical form of a client- or DB-supplied code, or null when the value
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* can't be a code at all. Everything that looks a code up, stores one, or
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* counts against one goes through here first.
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*/
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export const normalizeReferralCode = (value: unknown): string | null => {
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if (typeof value !== 'string') return null;
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const normalized = value.trim().toUpperCase();
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return REFERRAL_CODE_SHAPE.test(normalized) ? normalized : null;
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};
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/**
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* Mint a fresh code. Uniqueness is not this function's job — it is held by the
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* unique index on `user.referral_code`, and callers retry on violation.
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*
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* `crypto.randomInt` rather than `Math.random`: a code that can be derived from
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* an account id (as an earlier seeded-RNG version could) lets anyone
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* reconstruct another user's code and spend their referral allowance for them.
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*/
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export const generateReferralCode = (length = REFERRAL_CODE_LENGTH): string => {
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let code = '';
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for (let i = 0; i < length; i++) {
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code += MINT_ALPHABET[crypto.randomInt(0, MINT_ALPHABET.length)];
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}
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return code;
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};
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