fix(notes): drop expired notes and match geohash tags case-insensitively

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

@@ -20,6 +20,19 @@ class LocationNotesManager private constructor() {
         private const val TAG = "LocationNotesManager"
         private const val MAX_NOTES_IN_MEMORY = 500
 
+        /** How often displayed notes are re-checked against their NIP-40 expiry. */
+        private const val EXPIRY_PRUNE_INTERVAL_MS = 60_000L
+
+        /**
+         * Drops notes whose NIP-40 expiry has passed. Their ids stay in
+         * `noteIDs`, so a relay replay cannot resurrect them.
+         */
+        internal fun pruneExpired(notes: List<Note>, nowMillis: Long): List<Note> =
+            notes.filter { note ->
+                val expiresAt = note.expiresAtSeconds ?: return@filter true
+                expiresAt * 1000L > nowMillis
+            }
+
         @Volatile
         private var INSTANCE: LocationNotesManager? = null
 
@@ -38,7 +51,9 @@ class LocationNotesManager private constructor() {
         val pubkey: String,
         val content: String,
         val createdAt: Int,
-        val nickname: String?
+        val nickname: String?,
+        /** NIP-40 expiry as unix seconds, when the note carries one. */
+        val expiresAtSeconds: Long? = null
     ) {
         /**
          * Display name for the note - matches iOS exactly
@@ -99,6 +114,7 @@ class LocationNotesManager private constructor() {
     private var liveLocationToken: Long? = null
     private var subscribeRetryJob: Job? = null
     private var initialLoadJob: Job? = null
+    private var expiryPruneJob: Job? = null
 
     init {
         LiveLocationPrivacyGate.addRevocationListener(::stop)
@@ -370,7 +386,18 @@ class LocationNotesManager private constructor() {
         }
 
         _state.value = State.LOADING
-
+
+        // A note can expire while it is on screen (a 24h dead drop crossing its
+        // boundary). Filtering at ingest alone would keep it visible until the
+        // subscription is recreated, so re-check the displayed notes as well.
+        expiryPruneJob?.cancel()
+        expiryPruneJob = scope.launch {
+            while (isActive) {
+                delay(EXPIRY_PRUNE_INTERVAL_MS)
+                pruneExpiredNotes()
+            }
+        }
+
         // Subscribe for each geohash in the ±1 set
         subscribedGeohashes.forEach { gh ->
             if (!LiveLocationPrivacyGate.accepts(token)) return
@@ -417,23 +444,30 @@ class LocationNotesManager private constructor() {
             return
         }
 
-        // Check for geohash tag
-        val geohashTag = event.tags.firstOrNull { it.size >= 2 && it[0] == "g" }
-        if (geohashTag == null) {
-            Log.v(TAG, "Ignoring event without geohash tag: ${event.id.take(16)}...")
-            return
+        // Check for geohash tag. Tag names and geohashes are case-insensitive,
+        // and iOS matches them lowercased, so a note tagged ["G", "U4PRUYD"]
+        // has to be the same note on both platforms.
+        val validGeohashes = subscribedGeohashes.map { it.lowercase() }.toSet()
+        val geohashTag = event.tags.firstOrNull {
+            it.size >= 2 && it[0].lowercase() == "g" && validGeohashes.contains(it[1].lowercase())
         }
-
-        // Check if matches current geohash
-        val eventGeohash = geohashTag[1]
-        if (!subscribedGeohashes.contains(eventGeohash)) {
+        if (geohashTag == null) {
+            Log.v(TAG, "Ignoring event without a matching geohash tag: ${event.id.take(16)}...")
             return
         }
-        
+
         // Deduplicate
         if (noteIDs.contains(event.id)) {
             return
         }
+
+        // NIP-40: relays are not required to drop expired events, so enforce it
+        // here - otherwise a 24h dead drop stays visible past its expiry.
+        val expiresAt = expirationSeconds(event)
+        if (expiresAt != null && expiresAt * 1000L <= System.currentTimeMillis()) {
+            Log.v(TAG, "Ignoring expired note: ${event.id.take(16)}...")
+            return
+        }
 
         // Extract nickname from tags
         val nicknameTag = event.tags.firstOrNull { it.size >= 2 && it[0] == "n" }
@@ -445,7 +479,8 @@ class LocationNotesManager private constructor() {
             pubkey = event.pubkey,
             content = event.content,
             createdAt = event.createdAt,
-            nickname = nickname
+            nickname = nickname,
+            expiresAtSeconds = expiresAt
         )
 
         // Add to collection
@@ -465,6 +500,27 @@ class LocationNotesManager private constructor() {
         _state.value = State.READY
     }
 
+    /**
+     * The NIP-40 `expiration` tag as unix seconds, when the event carries one.
+     */
+    private fun expirationSeconds(event: NostrEvent): Long? {
+        val tag = event.tags.firstOrNull { it.size >= 2 && it[0].lowercase() == "expiration" }
+            ?: return null
+        return tag[1].toLongOrNull()
+    }
+
+    /**
+     * Drops displayed notes whose NIP-40 expiry has passed.
+     */
+    private fun pruneExpiredNotes() {
+        val current = _notes.value ?: return
+        val remaining = pruneExpired(current, System.currentTimeMillis())
+        // Ids stay in noteIDs so a relay replay cannot resurrect a dropped note.
+        if (remaining.size != current.size) {
+            _notes.value = remaining
+        }
+    }
+
     /**
      * Trim oldest notes to stay within memory limit
      */
@@ -497,6 +553,8 @@ class LocationNotesManager private constructor() {
         subscribeRetryJob = null
         initialLoadJob?.cancel()
         initialLoadJob = null
+        expiryPruneJob?.cancel()
+        expiryPruneJob = null
 
         if (subscriptionIDs.isNotEmpty()) {
             subscriptionIDs.values.forEach { subId ->

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

@@ -191,18 +191,24 @@ data class NostrFilter(
             return false
         }
 
-        // Check tag filters
+        // Check tag filters.
+        //
+        // Tag names and values are compared case-insensitively. The values this
+        // app filters on are hex ids (`e`, `p`) or geohashes (`g`), and both
+        // encode the same value in either case; iOS has no client-side filter at
+        // all and lowercases the tag name and the geohash where it reads them,
+        // so an event tagged ["G", "U4PRUYD"] is a note there. Comparing exactly
+        // here dropped it before any handler saw it.
         if (tagFilters != null) {
             for ((tagName, requiredValues) in tagFilters) {
-                val eventTags = event.tags.filter { it.isNotEmpty() && it[0] == tagName }
-                val eventValues = eventTags.mapNotNull { tag ->
-                    if (tag.size > 1) tag[1] else null
-                }
-
+                val eventValues = event.tags
+                    .filter { it.size > 1 && it[0].equals(tagName, ignoreCase = true) }
+                    .map { it[1].lowercase() }
+
                 val hasMatch = requiredValues.any { requiredValue ->
-                    eventValues.contains(requiredValue)
+                    eventValues.contains(requiredValue.lowercase())
                 }
-                
+
                 if (!hasMatch) {
                     return false
                 }

app/src/test/java/com/bitchat/android/nostr/LocationNotesCaseAndExpiryTest.kt

@@ -0,0 +1,71 @@
+package com.bitchat.android.nostr
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * Two places Android disagreed with iOS on the same note event: the case of the
+ * geohash tag, and a NIP-40 expiry that passes while the note is displayed.
+ */
+class LocationNotesCaseAndExpiryTest {
+
+    private fun note(id: String, expiresAtSeconds: Long?) = LocationNotesManager.Note(
+        id = id,
+        pubkey = "a".repeat(64),
+        content = "hi",
+        createdAt = 1_700_000_000,
+        nickname = null,
+        expiresAtSeconds = expiresAtSeconds
+    )
+
+    private fun event(tags: List<List<String>>) = NostrEvent(
+        id = "b".repeat(64),
+        pubkey = "a".repeat(64),
+        createdAt = 1_700_000_000,
+        kind = NostrKind.TEXT_NOTE,
+        tags = tags,
+        content = "hi"
+    )
+
+    @Test
+    fun `an uppercase geohash tag passes the subscription filter`() {
+        val filter = NostrFilter.geohashNotes(geohash = "u4pruyd")
+
+        assertTrue(filter.matches(event(listOf(listOf("g", "u4pruyd")))))
+        // iOS has no client-side filter and lowercases where it reads the tag,
+        // so this note is visible there; it has to reach the handler here too.
+        assertTrue(filter.matches(event(listOf(listOf("G", "U4PRUYD")))))
+    }
+
+    @Test
+    fun `a different geohash is still rejected`() {
+        val filter = NostrFilter.geohashNotes(geohash = "u4pruyd")
+
+        assertFalse(filter.matches(event(listOf(listOf("g", "u4pruye")))))
+        assertFalse(filter.matches(event(listOf(listOf("g")))))
+    }
+
+    @Test
+    fun `a note is dropped once its expiry passes`() {
+        val now = 1_700_000_000_000L
+        val notes = listOf(
+            note("plain", expiresAtSeconds = null),
+            note("later", expiresAtSeconds = 1_700_000_060L),
+            note("gone", expiresAtSeconds = 1_699_999_940L)
+        )
+
+        val remaining = LocationNotesManager.pruneExpired(notes, now)
+
+        assertEquals(listOf("plain", "later"), remaining.map { it.id })
+    }
+
+    @Test
+    fun `pruning at the expiry instant drops the note`() {
+        val notes = listOf(note("edge", expiresAtSeconds = 1_700_000_000L))
+
+        assertTrue(LocationNotesManager.pruneExpired(notes, 1_699_999_999_000L).isNotEmpty())
+        assertTrue(LocationNotesManager.pruneExpired(notes, 1_700_000_000_000L).isEmpty())
+    }
+}