Check bluetooth state prior to connecting

core/src/appleMain/kotlin/CentralManagerDelegate.kt

@@ -7,10 +7,13 @@ import com.juul.kable.CentralManagerDelegate.Response.DidDiscoverPeripheral
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asSharedFlow
+import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.filterNotNull
 import platform.CoreBluetooth.CBCentralManager
 import platform.CoreBluetooth.CBCentralManagerDelegateProtocol
+import platform.CoreBluetooth.CBCentralManagerStateUnknown
 import platform.CoreBluetooth.CBManagerState
 import platform.CoreBluetooth.CBPeripheral
 import platform.Foundation.NSError
@@ -24,8 +27,8 @@ internal class CentralManagerDelegate : NSObject(), CBCentralManagerDelegateProt
     private val _onDisconnected = MutableSharedFlow<NSUUID>()
     internal val onDisconnected = _onDisconnected.asSharedFlow()
 
-    private val _state = MutableStateFlow<CBManagerState?>(null)
-    val state: Flow<CBManagerState> = _state.filterNotNull()
+    private val _state = MutableStateFlow(CBCentralManagerStateUnknown)
+    val state: StateFlow<CBManagerState> = _state.asStateFlow()
 
     sealed class Response {
 

core/src/appleMain/kotlin/Peripheral.kt

@@ -53,7 +53,13 @@ import kotlinx.coroutines.flow.takeWhile
 import kotlinx.coroutines.job
 import kotlinx.coroutines.sync.withPermit
 import kotlinx.coroutines.withContext
+import platform.CoreBluetooth.CBCentralManagerState
 import platform.CoreBluetooth.CBCentralManagerStatePoweredOff
+import platform.CoreBluetooth.CBCentralManagerStatePoweredOn
+import platform.CoreBluetooth.CBCentralManagerStateResetting
+import platform.CoreBluetooth.CBCentralManagerStateUnauthorized
+import platform.CoreBluetooth.CBCentralManagerStateUnknown
+import platform.CoreBluetooth.CBCentralManagerStateUnsupported
 import platform.CoreBluetooth.CBCharacteristicWriteType
 import platform.CoreBluetooth.CBCharacteristicWriteWithResponse
 import platform.CoreBluetooth.CBCharacteristicWriteWithoutResponse
@@ -224,6 +230,8 @@ public class ApplePeripheral internal constructor(
     }
 
     public override suspend fun connect() {
+        // Check CBCentral State since connecting can result in an api misuse message
+        centralManager.checkBluetoothState(CBCentralManagerStatePoweredOn)
         connectJob.updateAndGet { it ?: connectAsync() }!!.await()
     }
 
@@ -430,3 +438,21 @@ private fun NSError.toStatus(): State.Disconnected.Status = when (code) {
     CBErrorEncryptionTimedOut -> EncryptionTimedOut
     else -> Unknown(code.toInt())
 }
+
+private fun CentralManager.checkBluetoothState(expected: CBCentralManagerState) {
+    val actual = delegate.state.value
+    if (expected != actual) {
+        fun nameFor(value: Number) = when (value) {
+            CBCentralManagerStatePoweredOff -> "PoweredOff"
+            CBCentralManagerStatePoweredOn -> "PoweredOn"
+            CBCentralManagerStateResetting -> "Resetting"
+            CBCentralManagerStateUnauthorized -> "Unauthorized"
+            CBCentralManagerStateUnknown -> "Unknown"
+            CBCentralManagerStateUnsupported -> "Unsupported"
+            else -> "Unknown"
+        }
+        val actualName = nameFor(actual)
+        val expectedName = nameFor(expected)
+        throw BluetoothDisabledException("Bluetooth state is $actualName ($actual), but $expectedName ($expected) was required.")
+    }
+}