Implement Geohash Presence (Heartbeats) (#576)

* geohash announce

* only for some geohashes

* global presence right away

* jitter delays

* show ? people for high-precision geohashes

* 1000 events

app/src/main/java/com/bitchat/android/nostr/GeohashMessageHandler.kt

@@ -46,15 +46,17 @@ class GeohashMessageHandler(
     fun onEvent(event: NostrEvent, subscribedGeohash: String) {
         scope.launch(Dispatchers.Default) {
             try {
-                if (event.kind != 20000) return@launch
+                if (event.kind != NostrKind.EPHEMERAL_EVENT && event.kind != NostrKind.GEOHASH_PRESENCE) return@launch
                 val tagGeo = event.tags.firstOrNull { it.size >= 2 && it[0] == "g" }?.getOrNull(1)
                 if (tagGeo == null || !tagGeo.equals(subscribedGeohash, true)) return@launch
                 if (dedupe(event.id)) return@launch
 
-                // PoW validation (if enabled)
-                val pow = PoWPreferenceManager.getCurrentSettings()
-                if (pow.enabled && pow.difficulty > 0) {
-                    if (!NostrProofOfWork.validateDifficulty(event, pow.difficulty)) return@launch
+                // PoW validation (if enabled) - apply to chat messages primarily
+                if (event.kind == NostrKind.EPHEMERAL_EVENT) {
+                    val pow = PoWPreferenceManager.getCurrentSettings()
+                    if (pow.enabled && pow.difficulty > 0) {
+                        if (!NostrProofOfWork.validateDifficulty(event, pow.difficulty)) return@launch
+                    }
                 }
 
                 // Blocked users check (use injected DataManager which has loaded state)
@@ -62,7 +64,12 @@ class GeohashMessageHandler(
 
                 // Update repository (participants, nickname, teleport)
                 // Update repository on a background-safe path; repository will post updates to LiveData
-                repo.updateParticipant(subscribedGeohash, event.pubkey, Date(event.createdAt * 1000L))
+                
+                // Update participant count (last seen) on BOTH Presence (20001) and Chat (20000) events
+                if (event.kind == NostrKind.GEOHASH_PRESENCE || event.kind == NostrKind.EPHEMERAL_EVENT) {
+                    repo.updateParticipant(subscribedGeohash, event.pubkey, Date(event.createdAt * 1000L))
+                }
+                
                 event.tags.find { it.size >= 2 && it[0] == "n" }?.let { repo.cacheNickname(event.pubkey, it[1]) }
                 event.tags.find { it.size >= 2 && it[0] == "t" && it[1] == "teleport" }?.let { repo.markTeleported(event.pubkey) }
                 // Register a geohash DM alias for this participant so MessageRouter can route DMs via Nostr
@@ -70,6 +77,9 @@ class GeohashMessageHandler(
                     com.bitchat.android.nostr.GeohashAliasRegistry.put("nostr_${event.pubkey.take(16)}", event.pubkey)
                 } catch (_: Exception) { }
 
+                // Stop here for presence events - they don't produce chat messages
+                if (event.kind == NostrKind.GEOHASH_PRESENCE) return@launch
+
                 // Skip our own events for message emission
                 val my = NostrIdentityBridge.deriveIdentity(subscribedGeohash, application)
                 if (my.publicKeyHex.equals(event.pubkey, true)) return@launch

app/src/main/java/com/bitchat/android/nostr/NostrEvent.kt

@@ -215,6 +215,7 @@ object NostrKind {
     const val SEAL = 13              // NIP-17 sealed event
     const val GIFT_WRAP = 1059       // NIP-17 gift wrap
     const val EPHEMERAL_EVENT = 20000 // For geohash channels
+    const val GEOHASH_PRESENCE = 20001 // For geohash presence heartbeat
 }
 
 /**

app/src/main/java/com/bitchat/android/nostr/NostrFilter.kt

@@ -32,11 +32,11 @@ data class NostrFilter(
         }
         
         /**
-         * Create filter for geohash-scoped ephemeral events (kind 20000)
+         * Create filter for geohash-scoped ephemeral events (kind 20000 and 20001)
          */
-        fun geohashEphemeral(geohash: String, since: Long? = null, limit: Int = 200): NostrFilter {
+        fun geohashEphemeral(geohash: String, since: Long? = null, limit: Int = 1000): NostrFilter {
             return NostrFilter(
-                kinds = listOf(NostrKind.EPHEMERAL_EVENT),
+                kinds = listOf(NostrKind.EPHEMERAL_EVENT, NostrKind.GEOHASH_PRESENCE),
                 since = since?.let { (it / 1000).toInt() },
                 tagFilters = mapOf("g" to listOf(geohash)),
                 limit = limit

app/src/main/java/com/bitchat/android/nostr/NostrProtocol.kt

@@ -117,6 +117,28 @@ object NostrProtocol {
         
         return@withContext senderIdentity.signEvent(event)
     }
+
+    /**
+     * Create a geohash-scoped presence event (kind 20001)
+     * Has no content and no nickname, used for participant counting
+     */
+    suspend fun createGeohashPresenceEvent(
+        geohash: String,
+        senderIdentity: NostrIdentity
+    ): NostrEvent = withContext(Dispatchers.Default) {
+        val tags = mutableListOf<List<String>>()
+        tags.add(listOf("g", geohash))
+
+        val event = NostrEvent(
+            pubkey = senderIdentity.publicKeyHex,
+            createdAt = (System.currentTimeMillis() / 1000).toInt(),
+            kind = NostrKind.GEOHASH_PRESENCE,
+            tags = tags,
+            content = ""
+        )
+
+        return@withContext senderIdentity.signEvent(event)
+    }
     
     /**
      * Create a geohash-scoped ephemeral public message (kind 20000)