import { ClientEvent, type ClientEventName, PROTOCOL_VERSION, type Rejection, type RejectionCode, clientMessageSchemas, } from '@volleyland/contracts'; import type { z } from 'zod'; import { TokenBucket } from './token-bucket.js'; type Parsed = z.infer<(typeof clientMessageSchemas)[E]>; export type GuardResult = { ok: true; message: Parsed } | Rejection; /** Burst capacity and sustained rate per event. Clients send player.input at 20/s; the blaster fires about 4–5 shots a second. */ export const RATE_LIMITS: Record = { [ClientEvent.RoomJoin]: { capacity: 3, perSecond: 0.2 }, [ClientEvent.PlayerInput]: { capacity: 10, perSecond: 25 }, [ClientEvent.ProjectileRequest]: { capacity: 4, perSecond: 8 }, [ClientEvent.WeaponSelect]: { capacity: 4, perSecond: 4 }, [ClientEvent.QuestionAnswer]: { capacity: 3, perSecond: 2 }, }; const rejection = (code: RejectionCode, message: string): Rejection => ({ ok: false, code, message }); /** * Per-connection admission control for client commands, cheapest check first: * rate limit → protocol version → schema → match → sequence. */ export class CommandGuard { private lastSeq = -1; private readonly buckets: Record; constructor(now: number) { this.buckets = Object.fromEntries( Object.entries(RATE_LIMITS).map(([event, limit]) => [event, new TokenBucket(limit.capacity, limit.perSecond, now)]), ) as Record; } /** * `matchId` is the match the connection is in right now (null before it joins). It is passed in * rather than remembered because an admin change can replace the room's match at any time. */ admit(event: E, raw: unknown, now: number, matchId: string | null): GuardResult { if (!this.buckets[event].tryTake(now)) return rejection('rate_limited', `Too many ${event} messages`); const version = typeof raw === 'object' && raw !== null ? (raw as { v?: unknown }).v : undefined; if (version !== PROTOCOL_VERSION) return rejection('protocol_mismatch', `Expected protocol version ${PROTOCOL_VERSION}`); const parsed = clientMessageSchemas[event].safeParse(raw); if (!parsed.success) return rejection('invalid_payload', parsed.error.issues[0]?.message ?? 'Invalid payload'); const message = parsed.data as Parsed; if (event === ClientEvent.RoomJoin) { if (matchId !== null) return rejection('not_allowed', 'Already in a room'); } else { if (matchId === null) return rejection('not_in_room', 'Join a room first'); if (message.matchId !== matchId) return rejection('wrong_match', 'Message is for a different match'); } if (message.seq <= this.lastSeq) return rejection('stale_sequence', `Sequence ${message.seq} is not after ${this.lastSeq}`); this.lastSeq = message.seq; return { ok: true, message }; } }