initial commit - chats working

app/src/main/java/com/mattintech/lchat/MainActivity.kt

@@ -0,0 +1,78 @@
+package com.mattintech.lchat
+
+import android.Manifest
+import android.util.Log
+import android.content.pm.PackageManager
+import android.os.Build
+import android.os.Bundle
+import androidx.activity.result.contract.ActivityResultContracts
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.content.ContextCompat
+import com.google.android.material.snackbar.Snackbar
+import com.mattintech.lchat.databinding.ActivityMainBinding
+import com.mattintech.lchat.utils.LOG_PREFIX
+
+class MainActivity : AppCompatActivity() {
+    
+    companion object {
+        private const val TAG = LOG_PREFIX + "MainActivity:"
+    }
+    
+    private lateinit var binding: ActivityMainBinding
+    
+    private val locationPermissionRequest = registerForActivityResult(
+        ActivityResultContracts.RequestMultiplePermissions()
+    ) { permissions ->
+        when {
+            permissions.getOrDefault(Manifest.permission.ACCESS_FINE_LOCATION, false) -> {
+                Log.d(TAG, "Location permission granted")
+            }
+            else -> {
+                Snackbar.make(
+                    binding.root,
+                    getString(R.string.permission_required),
+                    Snackbar.LENGTH_LONG
+                ).show()
+            }
+        }
+    }
+    
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        Log.d(TAG, "onCreate")
+        binding = ActivityMainBinding.inflate(layoutInflater)
+        setContentView(binding.root)
+        
+        setSupportActionBar(binding.toolbar)
+        checkPermissions()
+    }
+    
+    private fun checkPermissions() {
+        val permissionsToRequest = mutableListOf<String>()
+        
+        if (ContextCompat.checkSelfPermission(
+                this,
+                Manifest.permission.ACCESS_FINE_LOCATION
+            ) != PackageManager.PERMISSION_GRANTED
+        ) {
+            permissionsToRequest.add(Manifest.permission.ACCESS_FINE_LOCATION)
+        }
+        
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            if (ContextCompat.checkSelfPermission(
+                    this,
+                    Manifest.permission.NEARBY_WIFI_DEVICES
+                ) != PackageManager.PERMISSION_GRANTED
+            ) {
+                permissionsToRequest.add(Manifest.permission.NEARBY_WIFI_DEVICES)
+            }
+        }
+        
+        if (permissionsToRequest.isNotEmpty()) {
+            Log.d(TAG, "Requesting permissions: $permissionsToRequest")
+            locationPermissionRequest.launch(permissionsToRequest.toTypedArray())
+        } else {
+            Log.d(TAG, "All permissions already granted")
+        }
+    }
+}

app/src/main/java/com/mattintech/lchat/data/Message.kt

@@ -0,0 +1,10 @@
+package com.mattintech.lchat.data
+
+data class Message(
+    val id: String,
+    val senderId: String,
+    val senderName: String,
+    val content: String,
+    val timestamp: Long,
+    val isLocal: Boolean = false
+)

app/src/main/java/com/mattintech/lchat/data/User.kt

@@ -0,0 +1,8 @@
+package com.mattintech.lchat.data
+
+data class User(
+    val id: String,
+    val name: String,
+    val isHost: Boolean = false,
+    val lastSeen: Long = System.currentTimeMillis()
+)

app/src/main/java/com/mattintech/lchat/network/ChatService.kt

@@ -0,0 +1,20 @@
+package com.mattintech.lchat.network
+
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+
+class ChatService : Service() {
+    
+    override fun onBind(intent: Intent?): IBinder? {
+        return null
+    }
+    
+    override fun onCreate() {
+        super.onCreate()
+    }
+    
+    override fun onDestroy() {
+        super.onDestroy()
+    }
+}

app/src/main/java/com/mattintech/lchat/network/WifiAwareManager.kt

@@ -0,0 +1,230 @@
+package com.mattintech.lchat.network
+
+import android.content.Context
+import android.net.ConnectivityManager
+import android.net.NetworkCapabilities
+import android.net.NetworkRequest
+import android.net.wifi.aware.*
+import android.os.Build
+import android.util.Log
+import androidx.annotation.RequiresApi
+import com.mattintech.lchat.utils.LOG_PREFIX
+import java.util.concurrent.ConcurrentHashMap
+
+@RequiresApi(Build.VERSION_CODES.O)
+class WifiAwareManager(private val context: Context) {
+    
+    companion object {
+        private const val TAG = LOG_PREFIX + "WifiAwareManager:"
+        private const val SERVICE_NAME = "lchat"
+        private const val PORT = 8888
+    }
+    
+    private var wifiAwareManager: android.net.wifi.aware.WifiAwareManager? = null
+    private var wifiAwareSession: WifiAwareSession? = null
+    private var publishDiscoverySession: PublishDiscoverySession? = null
+    private var subscribeDiscoverySession: SubscribeDiscoverySession? = null
+    
+    private val peerHandles = ConcurrentHashMap<String, PeerHandle>()
+    private var messageCallback: ((String, String, String) -> Unit)? = null
+    private var connectionCallback: ((String, Boolean) -> Unit)? = null
+    
+    private val attachCallback = object : AttachCallback() {
+        override fun onAttached(session: WifiAwareSession) {
+            Log.d(TAG, "Wi-Fi Aware attached")
+            wifiAwareSession = session
+        }
+        
+        override fun onAttachFailed() {
+            Log.e(TAG, "Wi-Fi Aware attach failed")
+        }
+    }
+    
+    fun initialize() {
+        wifiAwareManager = context.getSystemService(Context.WIFI_AWARE_SERVICE) as? android.net.wifi.aware.WifiAwareManager
+        
+        if (wifiAwareManager?.isAvailable == true) {
+            wifiAwareManager?.attach(attachCallback, null)
+        } else {
+            Log.e(TAG, "Wi-Fi Aware is not available")
+        }
+    }
+    
+    fun startHostMode(roomName: String) {
+        val config = PublishConfig.Builder()
+            .setServiceName(SERVICE_NAME)
+            .setServiceSpecificInfo(roomName.toByteArray())
+            .build()
+            
+        wifiAwareSession?.publish(config, object : DiscoverySessionCallback() {
+            override fun onPublishStarted(session: PublishDiscoverySession) {
+                Log.d(TAG, "Publish started for room: $roomName")
+                publishDiscoverySession = session
+            }
+            
+            override fun onMessageReceived(peerHandle: PeerHandle, message: ByteArray) {
+                val messageStr = String(message)
+                Log.d(TAG, "Host: Received message: $messageStr")
+                
+                if (messageStr == "CONNECT_REQUEST") {
+                    Log.d(TAG, "Host: Received connection request")
+                    acceptConnection(peerHandle)
+                } else {
+                    handleIncomingMessage(peerHandle, message)
+                }
+            }
+        }, null)
+    }
+    
+    fun startClientMode() {
+        val config = SubscribeConfig.Builder()
+            .setServiceName(SERVICE_NAME)
+            .build()
+            
+        wifiAwareSession?.subscribe(config, object : DiscoverySessionCallback() {
+            override fun onSubscribeStarted(session: SubscribeDiscoverySession) {
+                Log.d(TAG, "Subscribe started")
+                subscribeDiscoverySession = session
+            }
+            
+            override fun onServiceDiscovered(
+                peerHandle: PeerHandle,
+                serviceSpecificInfo: ByteArray?,
+                matchFilter: List<ByteArray>?
+            ) {
+                val roomName = serviceSpecificInfo?.let { String(it) } ?: "Unknown"
+                Log.d(TAG, "Discovered room: $roomName")
+                
+                // Store peer handle for this room
+                peerHandles[roomName] = peerHandle
+                
+                // Send connection request to host
+                Log.d(TAG, "Sending connection request to room: $roomName")
+                subscribeDiscoverySession?.sendMessage(peerHandle, 0, "CONNECT_REQUEST".toByteArray())
+                
+                // Wait a bit for host to prepare, then connect
+                android.os.Handler(android.os.Looper.getMainLooper()).postDelayed({
+                    connectToPeer(peerHandle, roomName)
+                }, 500)
+            }
+            
+            override fun onMessageReceived(peerHandle: PeerHandle, message: ByteArray) {
+                handleIncomingMessage(peerHandle, message)
+            }
+        }, null)
+    }
+    
+    private fun connectToPeer(peerHandle: PeerHandle, roomName: String) {
+        Log.d(TAG, "connectToPeer: Starting connection to room: $roomName")
+        val networkSpecifier = WifiAwareNetworkSpecifier.Builder(subscribeDiscoverySession!!, peerHandle)
+            .setPskPassphrase("lchat-secure-key")
+            .build()
+            
+        val networkRequest = NetworkRequest.Builder()
+            .addTransportType(NetworkCapabilities.TRANSPORT_WIFI_AWARE)
+            .setNetworkSpecifier(networkSpecifier)
+            .build()
+            
+        Log.d(TAG, "connectToPeer: Network request created for room: $roomName")
+            
+        val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+        
+        try {
+            connectivityManager.requestNetwork(networkRequest, object : ConnectivityManager.NetworkCallback() {
+                override fun onAvailable(network: android.net.Network) {
+                    Log.d(TAG, "onAvailable: Network connected for room: $roomName")
+                    connectionCallback?.invoke(roomName, true)
+                }
+                
+                override fun onLost(network: android.net.Network) {
+                    Log.d(TAG, "onLost: Network lost for room: $roomName")
+                    connectionCallback?.invoke(roomName, false)
+                }
+                
+                override fun onUnavailable() {
+                    Log.e(TAG, "onUnavailable: Network request failed for room: $roomName")
+                    connectionCallback?.invoke(roomName, false)
+                }
+                
+                override fun onCapabilitiesChanged(network: android.net.Network, networkCapabilities: NetworkCapabilities) {
+                    Log.d(TAG, "onCapabilitiesChanged: Capabilities changed for room: $roomName")
+                }
+                
+                override fun onLinkPropertiesChanged(network: android.net.Network, linkProperties: android.net.LinkProperties) {
+                    Log.d(TAG, "onLinkPropertiesChanged: Link properties changed for room: $roomName")
+                }
+            }, android.os.Handler(android.os.Looper.getMainLooper()), 30000) // 30 second timeout
+            
+            Log.d(TAG, "connectToPeer: Network request submitted for room: $roomName")
+        } catch (e: Exception) {
+            Log.e(TAG, "connectToPeer: Failed to request network", e)
+            connectionCallback?.invoke(roomName, false)
+        }
+    }
+    
+    private fun acceptConnection(peerHandle: PeerHandle) {
+        Log.d(TAG, "acceptConnection: Accepting connection from client")
+        val networkSpecifier = WifiAwareNetworkSpecifier.Builder(publishDiscoverySession!!, peerHandle)
+            .setPskPassphrase("lchat-secure-key")
+            .setPort(PORT)
+            .build()
+            
+        val networkRequest = NetworkRequest.Builder()
+            .addTransportType(NetworkCapabilities.TRANSPORT_WIFI_AWARE)
+            .setNetworkSpecifier(networkSpecifier)
+            .build()
+            
+        val connectivityManager = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+        connectivityManager.requestNetwork(networkRequest, object : ConnectivityManager.NetworkCallback() {
+            override fun onAvailable(network: android.net.Network) {
+                Log.d(TAG, "Client connected")
+                peerHandles[peerHandle.toString()] = peerHandle
+            }
+            
+            override fun onUnavailable() {
+                Log.e(TAG, "Failed to accept client connection - Check if Wi-Fi is enabled")
+            }
+        })
+    }
+    
+    private fun handleIncomingMessage(peerHandle: PeerHandle, message: ByteArray) {
+        try {
+            val messageStr = String(message)
+            val parts = messageStr.split("|", limit = 3)
+            if (parts.size == 3) {
+                messageCallback?.invoke(parts[0], parts[1], parts[2])
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Error parsing message", e)
+        }
+    }
+    
+    fun sendMessage(userId: String, userName: String, content: String) {
+        val message = "$userId|$userName|$content".toByteArray()
+        
+        if (publishDiscoverySession != null) {
+            peerHandles.values.forEach { peerHandle ->
+                publishDiscoverySession?.sendMessage(peerHandle, 0, message)
+            }
+        } else if (subscribeDiscoverySession != null) {
+            peerHandles.values.forEach { peerHandle ->
+                subscribeDiscoverySession?.sendMessage(peerHandle, 0, message)
+            }
+        }
+    }
+    
+    fun setMessageCallback(callback: (String, String, String) -> Unit) {
+        messageCallback = callback
+    }
+    
+    fun setConnectionCallback(callback: (String, Boolean) -> Unit) {
+        connectionCallback = callback
+    }
+    
+    fun stop() {
+        publishDiscoverySession?.close()
+        subscribeDiscoverySession?.close()
+        wifiAwareSession?.close()
+        peerHandles.clear()
+    }
+}

app/src/main/java/com/mattintech/lchat/network/WifiAwareManagerSingleton.kt

@@ -0,0 +1,20 @@
+package com.mattintech.lchat.network
+
+import android.content.Context
+
+object WifiAwareManagerSingleton {
+    private var instance: WifiAwareManager? = null
+    
+    fun getInstance(context: Context): WifiAwareManager {
+        if (instance == null) {
+            instance = WifiAwareManager(context.applicationContext)
+            instance!!.initialize()
+        }
+        return instance!!
+    }
+    
+    fun reset() {
+        instance?.stop()
+        instance = null
+    }
+}

app/src/main/java/com/mattintech/lchat/ui/ChatFragment.kt

@@ -0,0 +1,125 @@
+package com.mattintech.lchat.ui
+
+import android.os.Bundle
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.fragment.app.Fragment
+import androidx.navigation.fragment.navArgs
+import androidx.recyclerview.widget.LinearLayoutManager
+import com.mattintech.lchat.data.Message
+import com.mattintech.lchat.databinding.FragmentChatBinding
+import com.mattintech.lchat.network.WifiAwareManager
+import com.mattintech.lchat.network.WifiAwareManagerSingleton
+import com.mattintech.lchat.ui.adapters.MessageAdapter
+import com.mattintech.lchat.utils.LOG_PREFIX
+import java.util.UUID
+
+class ChatFragment : Fragment() {
+    
+    companion object {
+        private const val TAG = LOG_PREFIX + "ChatFragment:"
+    }
+    
+    private var _binding: FragmentChatBinding? = null
+    private val binding get() = _binding!!
+    
+    private val args: ChatFragmentArgs by navArgs()
+    private lateinit var wifiAwareManager: WifiAwareManager
+    private lateinit var messageAdapter: MessageAdapter
+    private val messages = mutableListOf<Message>()
+    private val userId = UUID.randomUUID().toString()
+    
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        Log.d(TAG, "onCreateView")
+        _binding = FragmentChatBinding.inflate(inflater, container, false)
+        return binding.root
+    }
+    
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        Log.d(TAG, "onViewCreated - room: ${args.roomName}, user: ${args.userName}, isHost: ${args.isHost}")
+        
+        setupUI()
+        setupWifiAware()
+    }
+    
+    private fun setupUI() {
+        messageAdapter = MessageAdapter()
+        binding.messagesRecyclerView.apply {
+            adapter = messageAdapter
+            layoutManager = LinearLayoutManager(context).apply {
+                stackFromEnd = true
+            }
+        }
+        
+        binding.sendButton.setOnClickListener {
+            sendMessage()
+        }
+        
+        binding.messageInput.setOnEditorActionListener { _, _, _ ->
+            sendMessage()
+            true
+        }
+    }
+    
+    private fun setupWifiAware() {
+        wifiAwareManager = WifiAwareManagerSingleton.getInstance(requireContext())
+        
+        wifiAwareManager.setMessageCallback { senderId, senderName, content ->
+            Log.d(TAG, "Message received - from: $senderName, content: $content")
+            val message = Message(
+                id = UUID.randomUUID().toString(),
+                senderId = senderId,
+                senderName = senderName,
+                content = content,
+                timestamp = System.currentTimeMillis(),
+                isLocal = senderId == userId
+            )
+            
+            activity?.runOnUiThread {
+                messages.add(message)
+                messageAdapter.submitList(messages.toList())
+                binding.messagesRecyclerView.smoothScrollToPosition(messages.size - 1)
+            }
+        }
+        
+        // No need to start host mode here - already started in LobbyFragment
+        Log.d(TAG, "Chat setup complete - isHost: ${args.isHost}, room: ${args.roomName}")
+    }
+    
+    private fun sendMessage() {
+        val content = binding.messageInput.text?.toString()?.trim()
+        if (content.isNullOrEmpty()) return
+        
+        val message = Message(
+            id = UUID.randomUUID().toString(),
+            senderId = userId,
+            senderName = args.userName,
+            content = content,
+            timestamp = System.currentTimeMillis(),
+            isLocal = true
+        )
+        
+        messages.add(message)
+        messageAdapter.submitList(messages.toList())
+        binding.messagesRecyclerView.smoothScrollToPosition(messages.size - 1)
+        
+        Log.d(TAG, "Sending message: $content")
+        wifiAwareManager.sendMessage(userId, args.userName, content)
+        
+        binding.messageInput.text?.clear()
+    }
+    
+    override fun onDestroyView() {
+        super.onDestroyView()
+        Log.d(TAG, "onDestroyView")
+        // Don't stop WifiAwareManager here - it's shared across fragments
+        _binding = null
+    }
+}

app/src/main/java/com/mattintech/lchat/ui/LobbyFragment.kt

@@ -0,0 +1,130 @@
+package com.mattintech.lchat.ui
+
+import android.os.Bundle
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.Toast
+import androidx.fragment.app.Fragment
+import androidx.lifecycle.ViewModelProvider
+import androidx.navigation.fragment.findNavController
+import com.mattintech.lchat.R
+import com.mattintech.lchat.databinding.FragmentLobbyBinding
+import com.mattintech.lchat.network.WifiAwareManager
+import com.mattintech.lchat.network.WifiAwareManagerSingleton
+import com.mattintech.lchat.utils.LOG_PREFIX
+
+class LobbyFragment : Fragment() {
+    
+    companion object {
+        private const val TAG = LOG_PREFIX + "LobbyFragment:"
+    }
+    
+    private var _binding: FragmentLobbyBinding? = null
+    private val binding get() = _binding!!
+    
+    private lateinit var wifiAwareManager: WifiAwareManager
+    
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View {
+        Log.d(TAG, "onCreateView")
+        _binding = FragmentLobbyBinding.inflate(inflater, container, false)
+        return binding.root
+    }
+    
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        Log.d(TAG, "onViewCreated")
+        
+        Log.d(TAG, "Getting WifiAwareManager singleton")
+        wifiAwareManager = WifiAwareManagerSingleton.getInstance(requireContext())
+        
+        setupUI()
+    }
+    
+    private fun setupUI() {
+        binding.modeRadioGroup.setOnCheckedChangeListener { _, checkedId ->
+            when (checkedId) {
+                R.id.hostRadio -> {
+                    binding.roomLayout.visibility = View.VISIBLE
+                    binding.actionButton.text = getString(R.string.start_hosting)
+                    binding.roomsRecyclerView.visibility = View.GONE
+                    binding.noRoomsText.visibility = View.GONE
+                }
+                R.id.clientRadio -> {
+                    binding.roomLayout.visibility = View.GONE
+                    binding.actionButton.text = getString(R.string.search_rooms)
+                    binding.roomsRecyclerView.visibility = View.VISIBLE
+                }
+            }
+        }
+        
+        binding.actionButton.setOnClickListener {
+            val userName = binding.nameInput.text?.toString()?.trim()
+            
+            if (userName.isNullOrEmpty()) {
+                Toast.makeText(context, "Please enter your name", Toast.LENGTH_SHORT).show()
+                return@setOnClickListener
+            }
+            
+            when (binding.modeRadioGroup.checkedRadioButtonId) {
+                R.id.hostRadio -> {
+                    val roomName = binding.roomInput.text?.toString()?.trim()
+                    if (roomName.isNullOrEmpty()) {
+                        Toast.makeText(context, "Please enter a room name", Toast.LENGTH_SHORT).show()
+                        return@setOnClickListener
+                    }
+                    startHostMode(roomName, userName)
+                }
+                R.id.clientRadio -> {
+                    startClientMode(userName)
+                }
+            }
+        }
+        
+        wifiAwareManager.setConnectionCallback { roomName, isConnected ->
+            Log.d(TAG, "Connection callback - room: $roomName, connected: $isConnected")
+            activity?.runOnUiThread {
+                if (isConnected && binding.modeRadioGroup.checkedRadioButtonId == R.id.clientRadio) {
+                    val userName = binding.nameInput.text?.toString()?.trim() ?: ""
+                    navigateToChat(roomName, userName, false)
+                } else if (!isConnected && binding.modeRadioGroup.checkedRadioButtonId == R.id.clientRadio) {
+                    binding.noRoomsText.text = "Failed to connect to $roomName. Ensure Wi-Fi is enabled on both devices."
+                    Toast.makeText(context, "Connection failed. Check Wi-Fi is enabled.", Toast.LENGTH_LONG).show()
+                }
+            }
+        }
+    }
+    
+    private fun startHostMode(roomName: String, userName: String) {
+        Log.d(TAG, "Starting host mode - room: $roomName, user: $userName")
+        wifiAwareManager.startHostMode(roomName)
+        navigateToChat(roomName, userName, true)
+    }
+    
+    private fun startClientMode(userName: String) {
+        Log.d(TAG, "Starting client mode - user: $userName")
+        binding.noRoomsText.visibility = View.VISIBLE
+        binding.noRoomsText.text = getString(R.string.connecting)
+        wifiAwareManager.startClientMode()
+    }
+    
+    private fun navigateToChat(roomName: String, userName: String, isHost: Boolean) {
+        Log.d(TAG, "Navigating to chat - room: $roomName, user: $userName, isHost: $isHost")
+        val action = LobbyFragmentDirections.actionLobbyToChat(
+            roomName = roomName,
+            userName = userName,
+            isHost = isHost
+        )
+        findNavController().navigate(action)
+    }
+    
+    override fun onDestroyView() {
+        super.onDestroyView()
+        _binding = null
+    }
+}

app/src/main/java/com/mattintech/lchat/ui/adapters/MessageAdapter.kt

@@ -0,0 +1,69 @@
+package com.mattintech.lchat.ui.adapters
+
+import android.view.LayoutInflater
+import android.view.ViewGroup
+import androidx.constraintlayout.widget.ConstraintLayout
+import androidx.core.content.ContextCompat
+import androidx.recyclerview.widget.DiffUtil
+import androidx.recyclerview.widget.ListAdapter
+import androidx.recyclerview.widget.RecyclerView
+import com.mattintech.lchat.R
+import com.mattintech.lchat.data.Message
+import com.mattintech.lchat.databinding.ItemMessageBinding
+import java.text.SimpleDateFormat
+import java.util.*
+
+class MessageAdapter : ListAdapter<Message, MessageAdapter.MessageViewHolder>(MessageDiffCallback()) {
+    
+    private val timeFormat = SimpleDateFormat("HH:mm", Locale.getDefault())
+    
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MessageViewHolder {
+        val binding = ItemMessageBinding.inflate(
+            LayoutInflater.from(parent.context),
+            parent,
+            false
+        )
+        return MessageViewHolder(binding)
+    }
+    
+    override fun onBindViewHolder(holder: MessageViewHolder, position: Int) {
+        holder.bind(getItem(position))
+    }
+    
+    inner class MessageViewHolder(
+        private val binding: ItemMessageBinding
+    ) : RecyclerView.ViewHolder(binding.root) {
+        
+        fun bind(message: Message) {
+            binding.senderName.text = message.senderName
+            binding.messageContent.text = message.content
+            binding.timestamp.text = timeFormat.format(Date(message.timestamp))
+            
+            val layoutParams = binding.messageCard.layoutParams as ConstraintLayout.LayoutParams
+            if (message.isLocal) {
+                layoutParams.startToStart = ConstraintLayout.LayoutParams.UNSET
+                layoutParams.endToEnd = ConstraintLayout.LayoutParams.PARENT_ID
+                binding.messageCard.setCardBackgroundColor(
+                    ContextCompat.getColor(binding.root.context, R.color.purple_200)
+                )
+            } else {
+                layoutParams.startToStart = ConstraintLayout.LayoutParams.PARENT_ID
+                layoutParams.endToEnd = ConstraintLayout.LayoutParams.UNSET
+                binding.messageCard.setCardBackgroundColor(
+                    ContextCompat.getColor(binding.root.context, R.color.teal_200)
+                )
+            }
+            binding.messageCard.layoutParams = layoutParams
+        }
+    }
+    
+    class MessageDiffCallback : DiffUtil.ItemCallback<Message>() {
+        override fun areItemsTheSame(oldItem: Message, newItem: Message): Boolean {
+            return oldItem.id == newItem.id
+        }
+        
+        override fun areContentsTheSame(oldItem: Message, newItem: Message): Boolean {
+            return oldItem == newItem
+        }
+    }
+}

app/src/main/java/com/mattintech/lchat/utils/Constants.kt

@@ -0,0 +1,3 @@
+package com.mattintech.lchat.utils
+
+const val LOG_PREFIX = "LChat::"