Merge pull request #48 from ShilohEye/fix/android-ios-fragmentation-compatibility

Fix Android Message fragmentation for iOS compatibility

app/src/main/java/com/bitchat/android/mesh/BluetoothConnectionManager.kt

@@ -14,7 +14,8 @@ import kotlinx.coroutines.*
  */
 class BluetoothConnectionManager(
     private val context: Context, 
-    private val myPeerID: String
+    private val myPeerID: String,
+    private val fragmentManager: FragmentManager? = null
 ) : PowerManagerDelegate {
     
     companion object {
@@ -35,7 +36,7 @@ class BluetoothConnectionManager(
     // Component managers
     private val permissionManager = BluetoothPermissionManager(context)
     private val connectionTracker = BluetoothConnectionTracker(connectionScope, powerManager)
-    private val packetBroadcaster = BluetoothPacketBroadcaster(connectionScope, connectionTracker)
+    private val packetBroadcaster = BluetoothPacketBroadcaster(connectionScope, connectionTracker, fragmentManager)
     
     // Delegate for component managers to call back to main manager
     private val componentDelegate = object : BluetoothConnectionManagerDelegate {
@@ -156,6 +157,7 @@ class BluetoothConnectionManager(
 
     /**
      * Broadcast packet to connected devices with connection limit enforcement
+     * Automatically fragments large packets to fit within BLE MTU limits
      */
     fun broadcastPacket(routed: RoutedPacket) {
         if (!isActive) return

app/src/main/java/com/bitchat/android/mesh/BluetoothMeshService.kt

@@ -45,7 +45,7 @@ class BluetoothMeshService(private val context: Context) {
     private val securityManager = SecurityManager(encryptionService, myPeerID)
     private val storeForwardManager = StoreForwardManager()
     private val messageHandler = MessageHandler(myPeerID)
-    internal val connectionManager = BluetoothConnectionManager(context, myPeerID) // Made internal for access
+    internal val connectionManager = BluetoothConnectionManager(context, myPeerID, fragmentManager) // Made internal for access
     private val packetProcessor = PacketProcessor(myPeerID)
     
     // Service state management

app/src/main/java/com/bitchat/android/mesh/BluetoothPacketBroadcaster.kt

@@ -16,7 +16,8 @@ import kotlinx.coroutines.launch
  */
 class BluetoothPacketBroadcaster(
     private val connectionScope: CoroutineScope,
-    private val connectionTracker: BluetoothConnectionTracker
+    private val connectionTracker: BluetoothConnectionTracker,
+    private val fragmentManager: FragmentManager?
 ) {
     
     companion object {
@@ -24,9 +25,6 @@ class BluetoothPacketBroadcaster(
         private const val CLEANUP_DELAY = 500L
     }
     
-    /**
-     * Broadcast packet to connected devices with connection limit enforcement
-     */
     fun broadcastPacket(
         routed: RoutedPacket,
         gattServer: BluetoothGattServer?,
@@ -34,6 +32,37 @@ class BluetoothPacketBroadcaster(
     ) {
         val packet = routed.packet
         val data = packet.toBinaryData() ?: return
+            // Check if we need to fragment
+        if (fragmentManager != null) {
+            val fragments = fragmentManager.createFragments(packet)
+            if (fragments.size > 1) {
+                Log.d(TAG, "Fragmenting packet into ${fragments.size} fragments")
+                connectionScope.launch {
+                    fragments.forEach { fragment ->
+                        broadcastSinglePacket(RoutedPacket(fragment), gattServer, characteristic)
+                        // 20ms delay between fragments (matching iOS/Rust)
+                        delay(20)
+                    }
+                }
+                return
+            }
+        }
+        
+        // Send single packet if no fragmentation needed
+        broadcastSinglePacket(routed, gattServer, characteristic)
+    }
+
+    
+    /**
+     * Broadcast single packet to connected devices with connection limit enforcement
+     */
+    fun broadcastSinglePacket(
+        routed: RoutedPacket,
+        gattServer: BluetoothGattServer?,
+        characteristic: BluetoothGattCharacteristic?
+    ) {
+        val packet = routed.packet
+        val data = packet.toBinaryData() ?: return
         
         if (packet.recipientID != SpecialRecipients.BROADCAST) {
             val recipientID = packet.recipientID?.let {

app/src/main/java/com/bitchat/android/mesh/FragmentManager.kt

@@ -14,7 +14,7 @@ class FragmentManager {
     
     companion object {
         private const val TAG = "FragmentManager"
-        private const val MAX_FRAGMENT_SIZE = 500
+        private const val MAX_FRAGMENT_SIZE = 150  // Match iOS/Rust for BLE compatibility (185 byte MTU limit)
         private const val FRAGMENT_TIMEOUT = 30000L // 30 seconds
         private const val CLEANUP_INTERVAL = 10000L // 10 seconds
     }
@@ -46,16 +46,15 @@ class FragmentManager {
         val fragments = mutableListOf<BitchatPacket>()
         val fragmentID = generateFragmentID()
         
-        // Calculate header size (13 bytes for fragment metadata)
+        // Fragment overhead: 13 bytes (fragment metadata) + 21 bytes (packet header) = 34 bytes total
-        val headerSize = 13
+        // With 150 byte fragments, total packet = ~184 bytes (within iOS 185 byte MTU)
-        val dataPerFragment = MAX_FRAGMENT_SIZE - headerSize
+        val totalFragments = (data.size + MAX_FRAGMENT_SIZE - 1) / MAX_FRAGMENT_SIZE
-        val totalFragments = (data.size + dataPerFragment - 1) / dataPerFragment
         
         Log.d(TAG, "Creating ${totalFragments} fragments for ${data.size} byte packet")
         
         for (i in 0 until totalFragments) {
-            val start = i * dataPerFragment
+            val start = i * MAX_FRAGMENT_SIZE
-            val end = minOf(start + dataPerFragment, data.size)
+            val end = minOf(start + MAX_FRAGMENT_SIZE, data.size)
             val fragmentData = data.sliceArray(start until end)
             
             val fragmentPayload = createFragmentPayload(
@@ -158,7 +157,7 @@ class FragmentManager {
      * Create fragment payload with metadata
      */
     private fun createFragmentPayload(
-        fragmentID: String,
+        fragmentID: ByteArray,
         index: Int,
         total: Int,
         originalType: UByte,
@@ -167,8 +166,7 @@ class FragmentManager {
         val payload = ByteArray(13 + data.size)
         
         // Fragment ID (8 bytes)
-        val idBytes = fragmentID.toByteArray()
+        System.arraycopy(fragmentID, 0, payload, 0, 8)
-        System.arraycopy(idBytes, 0, payload, 0, minOf(8, idBytes.size))
         
         // Index (2 bytes, big-endian)
         payload[8] = ((index shr 8) and 0xFF).toByte()
@@ -188,10 +186,12 @@ class FragmentManager {
     }
     
     /**
-     * Generate unique fragment ID
+     * Generate unique fragment ID (8 random bytes to match iOS/Rust)
      */
-    private fun generateFragmentID(): String {
+    private fun generateFragmentID(): ByteArray {
-        return "${System.currentTimeMillis()}-${kotlin.random.Random.nextInt()}"
+        val fragmentID = ByteArray(8)
+        kotlin.random.Random.nextBytes(fragmentID)
+        return fragmentID
     }
     
     /**