chore: enforce max subscription & filter limits

src/@types/adapters.ts

@@ -1,4 +1,5 @@
 import { EventEmitter } from 'node:stream'
+import { SubscriptionFilter } from './subscription'
 
 export interface IWebSocketServerAdapter extends EventEmitter {
   getConnectedClients(): number
@@ -10,4 +11,6 @@ export interface IWebServerAdapter extends EventEmitter {
 }
 
 
-export type IWebSocketAdapter = EventEmitter
+export type IWebSocketAdapter = EventEmitter & {
+  getSubscriptions(): Map<string, Set<SubscriptionFilter>>
+}

src/@types/messages.ts

@@ -14,11 +14,12 @@ export type IncomingMessage =
   | SubscribeMessage
   | IncomingEventMessage
   | UnsubscribeMessage
-  | Notice
+
 
 export type OutgoingMessage =
   | OutgoingEventMessage
   | EndOfStoredEventsNotice
+  | NoticeMessage
 
 export type SubscribeMessage = {
   [index in Range<2, 100>]: SubscriptionFilter
@@ -44,7 +45,7 @@ export interface UnsubscribeMessage {
   1: SubscriptionId
 }
 
-export interface Notice {
+export interface NoticeMessage {
   0: MessageType.NOTICE
   1: string
 }

src/handlers/subscribe-message-handler.ts

@@ -1,7 +1,7 @@
-import { anyPass, map } from 'ramda'
+import { anyPass, equals, map, uniqWith } from 'ramda'
 import { pipeline } from 'stream/promises'
 
-import { createEndOfStoredEventsNoticeMessage, createOutgoingEventMessage } from '../utils/messages'
+import { createEndOfStoredEventsNoticeMessage, createNoticeMessage, createOutgoingEventMessage } from '../utils/messages'
 import { IAbortable, IMessageHandler } from '../@types/message-handlers'
 import { isEventMatchingFilter, toNostrEvent } from '../utils/event'
 import { streamEach, streamEnd, streamFilter, streamMap } from '../utils/stream'
@@ -9,10 +9,10 @@ import { SubscriptionFilter, SubscriptionId } from '../@types/subscription'
 import { Event } from '../@types/event'
 import { IEventRepository } from '../@types/repositories'
 import { IWebSocketAdapter } from '../@types/adapters'
+import { Settings } from '../utils/settings'
 import { SubscribeMessage } from '../@types/messages'
 import { WebSocketAdapterEvent } from '../constants/adapter'
 
-
 export class SubscribeMessageHandler implements IMessageHandler, IAbortable {
   private readonly abortController: AbortController
 
@@ -29,7 +29,13 @@ export class SubscribeMessageHandler implements IMessageHandler, IAbortable {
 
   public async handleMessage(message: SubscribeMessage): Promise<void> {
     const subscriptionId = message[1] as SubscriptionId
-    const filters = message.slice(2) as SubscriptionFilter[]
+    const filters = uniqWith(equals, message.slice(2)) as SubscriptionFilter[]
+
+    const reason = this.canSubscribe(subscriptionId, filters)
+    if (reason) {
+      this.webSocket.emit(WebSocketAdapterEvent.Message, createNoticeMessage(`Subscription request rejected: ${reason}`))
+      return
+    }
 
     this.webSocket.emit(WebSocketAdapterEvent.Subscribe, subscriptionId, new Set(filters))
 
@@ -59,4 +65,20 @@ export class SubscribeMessageHandler implements IMessageHandler, IAbortable {
     }
   }
 
+  private canSubscribe(subscriptionId: string, filters: SubscriptionFilter[]): string | undefined {
+    const maxSubscriptions = Settings.limits.client.subscription.maxSubscriptions
+    if (maxSubscriptions > 0) {
+      const subscriptions = this.webSocket.getSubscriptions()
+      if (!subscriptions.has(subscriptionId) && subscriptions.size + 1 > maxSubscriptions) {
+        return `Too many subscriptions: Number of subscriptions must be less than ${maxSubscriptions}`
+      }
+    }
+
+    const maxFilters = Settings.limits.client.subscription.maxFilters
+    if (maxFilters > 0) {
+      if (filters.length > maxFilters) {
+        return `Too many filters: Number of filters per susbscription must be less or equal to ${maxFilters}`
+      }
+    }
+  }
 }

src/utils/messages.ts

@@ -1,13 +1,13 @@
 import {
   EndOfStoredEventsNotice,
   MessageType,
-  Notice,
+  NoticeMessage,
   OutgoingMessage,
 } from '../@types/messages'
 import { Event } from '../@types/event'
 import { SubscriptionId } from '../@types/subscription'
 
-export const createNotice = (notice: string): Notice => {
+export const createNoticeMessage = (notice: string): NoticeMessage => {
   return [MessageType.NOTICE, notice]
 }
 

test/unit/utils/messages.spec.ts

@@ -1,12 +1,12 @@
 import { expect } from 'chai'
 
-import { createEndOfStoredEventsNoticeMessage, createNotice, createOutgoingEventMessage } from '../../../src/utils/messages'
+import { createEndOfStoredEventsNoticeMessage, createNoticeMessage, createOutgoingEventMessage } from '../../../src/utils/messages'
 import { Event } from '../../../src/@types/event'
 import { MessageType } from '../../../src/@types/messages'
 
 describe('createNotice', () => {
   it('returns a notice message', () => {
-    expect(createNotice('some notice')).to.deep.equal([MessageType.NOTICE, 'some notice'])
+    expect(createNoticeMessage('some notice')).to.deep.equal([MessageType.NOTICE, 'some notice'])
   })
 })