Only adds user to Hidden Users after 5 duplicated messages.

app/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -420,13 +420,13 @@ class Account(
         reconnectIfRelaysHaveChanged()
       }
     }
-    LocalCache.liveSpam.observeForever {
+    LocalCache.antiSpam.liveSpam.observeForever {
       GlobalScope.launch(Dispatchers.IO) {
-        LocalCache.spamMessages.snapshot().values.forEach {
-          if (it !in hiddenUsers) {
-            val userToBlock = LocalCache.getOrCreateUser(it)
+        it.cache.spamMessages.snapshot().values.forEach {
+          if (it.pubkeyHex !in transientHiddenUsers && it.duplicatedMessages > 5) {
+            val userToBlock = LocalCache.getOrCreateUser(it.pubkeyHex)
             if (userToBlock != userProfile() && userToBlock !in userProfile().follows) {
-              transientHiddenUsers = transientHiddenUsers + it
+              transientHiddenUsers = transientHiddenUsers + it.pubkeyHex
             }
           }
         }

app/src/main/java/com/vitorpamplona/amethyst/model/AntiSpamFilter.kt

@@ -0,0 +1,92 @@
+package com.vitorpamplona.amethyst.model
+
+import android.util.Log
+import android.util.LruCache
+import androidx.lifecycle.LiveData
+import java.util.concurrent.atomic.AtomicBoolean
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.NonCancellable
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import nostr.postr.events.Event
+import nostr.postr.toHex
+
+class AntiSpamFilter {
+  val recentMessages = LruCache<Int, String>(1000)
+  val spamMessages = LruCache<Int, Spammer>(1000)
+
+  @Synchronized
+  fun isSpam(event: Event): Boolean {
+    val idHex = event.id.toHexKey()
+
+    // if already processed, ok
+    if (LocalCache.notes[idHex] != null) return false
+
+    // if short message, ok
+    if (event.content.length < 50) return false
+
+    // double list strategy:
+    // if duplicated, it goes into spam. 1000 spam messages are saved into the spam list.
+
+    // Considers tags so that same replies to different people don't count.
+    val hash = (event.content + event.tags.flatten().joinToString(",")).hashCode()
+
+    if ((recentMessages[hash] != null && recentMessages[hash] != idHex) || spamMessages[hash] != null) {
+      Log.w("Potential SPAM Message", "${event.id.toHex()} ${recentMessages[hash]} ${spamMessages[hash] != null} ${event.content.replace("\n", " | ")}")
+
+      // Log down offenders
+      if (spamMessages.get(hash) == null) {
+        spamMessages.put(hash, Spammer(event.pubKey.toHexKey(), 2))
+        liveSpam.invalidateData()
+      } else {
+        spamMessages.get(hash).duplicatedMessages++
+        liveSpam.invalidateData()
+      }
+
+      return true
+    }
+
+    recentMessages.put(hash, idHex)
+
+    return false
+  }
+
+  val liveSpam: AntiSpamLiveData = AntiSpamLiveData(this)
+}
+
+
+class AntiSpamLiveData(val cache: AntiSpamFilter): LiveData<AntiSpamState>(AntiSpamState(cache)) {
+
+  // Refreshes observers in batches.
+  var handlerWaiting = AtomicBoolean()
+
+  @Synchronized
+  fun invalidateData() {
+    if (!hasActiveObservers()) return
+    if (handlerWaiting.getAndSet(true)) return
+
+    handlerWaiting.set(true)
+    val scope = CoroutineScope(Job() + Dispatchers.Main)
+    scope.launch {
+      try {
+        delay(100)
+        refresh()
+      } finally {
+        withContext(NonCancellable) {
+          handlerWaiting.set(false)
+        }
+      }
+    }
+  }
+
+  private fun refresh() {
+    postValue(AntiSpamState(cache))
+  }
+}
+
+class AntiSpamState(val cache: AntiSpamFilter) {
+
+}

app/src/main/java/com/vitorpamplona/amethyst/model/LocalCache.kt

@@ -41,21 +41,22 @@ import nostr.postr.events.PrivateDmEvent
 import nostr.postr.events.RecommendRelayEvent
 import nostr.postr.events.TextNoteEvent
 import nostr.postr.toHex
+import nostr.postr.toNpub
 
+data class Spammer(val pubkeyHex: HexKey, var duplicatedMessages: Int)
 
 object LocalCache {
   val metadataParser = jacksonObjectMapper()
     .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
     .readerFor(UserMetadata::class.java)
 
+  val antiSpam = AntiSpamFilter()
+
   val users = ConcurrentHashMap<HexKey, User>()
   val notes = ConcurrentHashMap<HexKey, Note>()
   val channels = ConcurrentHashMap<HexKey, Channel>()
 
-  val recentMessages = LruCache<Int, String>(1000)
-  val spamMessages = LruCache<Int, String>(1000)
-
-  fun checkGetOrCreateUser(key: HexKey): User? {
+  fun checkGetOrCreateUser(key: String): User? {
     return try {
       val checkHex = Hex.decode(key) // Checks if this is a valid Hex
       getOrCreateUser(key)
@@ -74,7 +75,7 @@ object LocalCache {
     }
   }
 
-  fun checkGetOrCreateNote(key: HexKey): Note? {
+  fun checkGetOrCreateNote(key: String): Note? {
     return try {
       val checkHex = Hex.decode(key) // Checks if this is a valid Hex
       getOrCreateNote(key)
@@ -93,7 +94,7 @@ object LocalCache {
     }
   }
 
-  fun checkGetOrCreateChannel(key: HexKey): Channel? {
+  fun checkGetOrCreateChannel(key: String): Channel? {
     return try {
       val checkHex = Hex.decode(key) // Checks if this is a valid Hex
       getOrCreateChannel(key)
@@ -141,29 +142,9 @@ object LocalCache {
       .format(DateTimeFormatter.ofPattern("uuuu MMM d hh:mm a"))
   }
 
-  @Synchronized
-  fun isRepeatedMessageSpam(event: Event): Boolean {
-    val idHex = event.id.toHexKey()
-    // if already processed, return
-    if (notes[idHex] != null) return false
-
-    // double list strategy:
-    // if duplicated, it goes into spam. 1000 spam messages are saved into the spam list.
-    val hash = (event.content + event.tags.flatten().joinToString(",")).hashCode()
-    if (event.content.length > 50 && ((recentMessages[hash] != null && recentMessages[hash] != idHex) || spamMessages[hash] != null)) {
-      Log.w("Potential SPAM Message", "${event.id.toHex()} ${recentMessages[hash]} ${spamMessages[hash] != null} ${event.content.replace("\n", " | ")}")
-      if (spamMessages.get(hash) == null) {
-        spamMessages.put(hash, event.pubKey.toHexKey())
-        liveSpam.invalidateData()
-      }
-      return true
-    }
-    recentMessages.put(hash, idHex)
-    return false
-  }
 
   fun consume(event: TextNoteEvent, relay: Relay? = null) {
-    if (isRepeatedMessageSpam(event)) return
+    if (antiSpam.isSpam(event)) return
 
     val note = getOrCreateNote(event.id.toHex())
     val author = getOrCreateUser(event.pubKey.toHexKey())
@@ -450,7 +431,7 @@ object LocalCache {
 
   fun consume(event: ChannelMessageEvent, relay: Relay?) {
     if (event.channel.isNullOrBlank()) return
-    if (isRepeatedMessageSpam(event)) return
+    if (antiSpam.isSpam(event)) return
 
     val channel = checkGetOrCreateChannel(event.channel) ?: return
 
@@ -667,7 +648,6 @@ object LocalCache {
 
   // Observers line up here.
   val live: LocalCacheLiveData = LocalCacheLiveData(this)
-  val liveSpam: LocalCacheLiveData = LocalCacheLiveData(this)
 
   private fun refreshObservers() {
     live.invalidateData()