feat: introduce Desktop target and expand Kotlin Multiplatform (KMP) architecture (#4761)

Signed-off-by: James Rich <2199651+jamesarich@users.noreply.github.com>

core/database/src/androidMain/kotlin/org/meshtastic/core/database/DatabaseManager.kt

@@ -42,10 +42,11 @@ import java.io.File
 import org.meshtastic.core.common.database.DatabaseManager as SharedDatabaseManager
 
 /** Manages per-device Room database instances for node data, with LRU eviction. */
-@Single
+@Single(binds = [DatabaseProvider::class, SharedDatabaseManager::class])
 @Suppress("TooManyFunctions")
 @OptIn(ExperimentalCoroutinesApi::class)
 open class DatabaseManager(private val app: Application, private val dispatchers: CoroutineDispatchers) :
+    DatabaseProvider,
     SharedDatabaseManager {
     val prefs: SharedPreferences = app.getSharedPreferences("db-manager-prefs", Context.MODE_PRIVATE)
     private val managerScope = CoroutineScope(SupervisorJob() + dispatchers.default)
@@ -69,7 +70,7 @@ open class DatabaseManager(private val app: Application, private val dispatchers
     }
 
     private val _currentDb = MutableStateFlow<MeshtasticDatabase?>(null)
-    val currentDb: StateFlow<MeshtasticDatabase> =
+    override val currentDb: StateFlow<MeshtasticDatabase> =
         _currentDb.filterNotNull().stateIn(managerScope, SharingStarted.Eagerly, buildRoomDb(app, defaultDbName()))
 
     private val _currentAddress = MutableStateFlow<String?>(null)
@@ -119,7 +120,7 @@ open class DatabaseManager(private val app: Application, private val dispatchers
     private val limitedIo = dispatchers.io.limitedParallelism(4)
 
     /** Execute [block] with the current DB instance. */
-    suspend fun <T> withDb(block: suspend (MeshtasticDatabase) -> T): T? = withContext(limitedIo) {
+    override suspend fun <T> withDb(block: suspend (MeshtasticDatabase) -> T): T? = withContext(limitedIo) {
         val db = _currentDb.value ?: return@withContext null
         val active = buildDbName(_currentAddress.value)
         markLastUsed(active)
@@ -127,7 +128,7 @@ open class DatabaseManager(private val app: Application, private val dispatchers
     }
 
     /** Returns true if a database exists for the given device address. */
-    fun hasDatabaseFor(address: String?): Boolean {
+    override fun hasDatabaseFor(address: String?): Boolean {
         if (address.isNullOrBlank() || address == "n") return false
         val dbName = buildDbName(address)
         return getDbFile(app, dbName) != null

core/database/src/commonMain/kotlin/org/meshtastic/core/database/DatabaseProvider.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2025-2026 Meshtastic LLC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.meshtastic.core.database
+
+import kotlinx.coroutines.flow.StateFlow
+
+/**
+ * Provides multiplatform access to the current [MeshtasticDatabase] and a safe transactional helper. Platform
+ * implementations manage the concrete lifecycle (Room on Android, etc.).
+ */
+interface DatabaseProvider {
+    /** Reactive stream of the currently active database instance. */
+    val currentDb: StateFlow<MeshtasticDatabase>
+
+    /** Execute [block] against the current database, returning `null` if no database is available. */
+    suspend fun <T> withDb(block: suspend (MeshtasticDatabase) -> T): T?
+}

core/database/src/commonMain/kotlin/org/meshtastic/core/database/dao/NodeInfoDao.kt

@@ -109,7 +109,7 @@ interface NodeInfoDao {
         val incomingKey = incomingNode.publicKey
 
         val incomingHasKey = (incomingKey?.size ?: 0) == KEY_SIZE
-        val existingHasKey = (existingKey?.size ?: 0) == KEY_SIZE && existingKey != NodeEntity.ERROR_BYTE_STRING
+        val existingHasKey = existingKey.size == KEY_SIZE && existingKey != NodeEntity.ERROR_BYTE_STRING
 
         return when {
             incomingHasKey -> {
@@ -143,7 +143,7 @@ interface NodeInfoDao {
 
         val isPlaceholder = incomingNode.user.hw_model == HardwareModel.UNSET
         val hasExistingUser = existingNode.user.hw_model != HardwareModel.UNSET
-        val isDefaultName = incomingNode.user.long_name?.matches(Regex("^Meshtastic [0-9a-fA-F]{4}$")) == true
+        val isDefaultName = incomingNode.user.long_name.matches(Regex("^Meshtastic [0-9a-fA-F]{4}$"))
 
         if (hasExistingUser && isPlaceholder && isDefaultName) {
             return incomingNode.copy(

core/database/src/commonMain/kotlin/org/meshtastic/core/database/entity/MeshLog.kt

@@ -27,6 +27,7 @@ import org.meshtastic.proto.MeshPacket
 import org.meshtastic.proto.MyNodeInfo
 import org.meshtastic.proto.NodeInfo
 import org.meshtastic.proto.Position
+import org.meshtastic.core.model.MeshLog as ExternalMeshLog
 
 /**
  * Represents a log entry in the database.
@@ -83,3 +84,23 @@ data class MeshLog(
         const val NODE_NUM_LOCAL = 0
     }
 }
+
+fun MeshLog.asExternalModel() = ExternalMeshLog(
+    uuid = uuid,
+    message_type = message_type,
+    received_date = received_date,
+    raw_message = raw_message,
+    fromNum = fromNum,
+    portNum = portNum,
+    fromRadio = fromRadio,
+)
+
+fun ExternalMeshLog.asEntity() = MeshLog(
+    uuid = uuid,
+    message_type = message_type,
+    received_date = received_date,
+    raw_message = raw_message,
+    fromNum = fromNum,
+    portNum = portNum,
+    fromRadio = fromRadio,
+)

core/database/src/commonMain/kotlin/org/meshtastic/core/database/entity/NodeEntity.kt

@@ -163,7 +163,7 @@ data class NodeEntity(
         get() = user.hw_model == HardwareModel.UNSET
 
     val hasPKC
-        get() = (publicKey ?: user.public_key)?.size?.let { it > 0 } == true
+        get() = (publicKey ?: user.public_key).size > 0
 
     fun setPosition(p: WirePosition, defaultTime: Int = currentTime()) {
         position = p.copy(time = if (p.time != 0) p.time else defaultTime)
@@ -216,8 +216,8 @@ data class NodeEntity(
         user =
         MeshUser(
             id = user.id,
-            longName = user.long_name ?: "",
-            shortName = user.short_name ?: "",
+            longName = user.long_name,
+            shortName = user.short_name,
             hwModel = user.hw_model,
             role = user.role.value,
         )
@@ -228,10 +228,10 @@ data class NodeEntity(
             longitude = longitude,
             altitude = position.altitude ?: 0,
             time = position.time,
-            satellitesInView = position.sats_in_view ?: 0,
+            satellitesInView = position.sats_in_view,
             groundSpeed = position.ground_speed ?: 0,
             groundTrack = position.ground_track ?: 0,
-            precisionBits = position.precision_bits ?: 0,
+            precisionBits = position.precision_bits,
         )
             .takeIf { it.isValid() },
         snr = snr,