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Make isSupported always true on Apple #752

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Oct 2, 2024
Merged

Make isSupported always true on Apple #752

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52 changes: 1 addition & 51 deletions kable-core/src/appleMain/kotlin/bluetooth/IsSupported.kt
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Original file line number Diff line number Diff line change
@@ -1,53 +1,3 @@
package com.juul.kable.bluetooth

import kotlinx.coroutines.channels.awaitClose
import kotlinx.coroutines.channels.onFailure
import kotlinx.coroutines.flow.callbackFlow
import kotlinx.coroutines.flow.first
import kotlinx.coroutines.sync.Mutex
import kotlinx.coroutines.sync.withLock
import platform.CoreBluetooth.CBCentralManager
import platform.CoreBluetooth.CBCentralManagerDelegateProtocol
import platform.CoreBluetooth.CBCentralManagerOptionShowPowerAlertKey
import platform.CoreBluetooth.CBManagerState
import platform.CoreBluetooth.CBManagerStateResetting
import platform.CoreBluetooth.CBManagerStateUnknown
import platform.CoreBluetooth.CBManagerStateUnsupported
import platform.darwin.NSObject

// Prevent triggering bluetooth dialog (note that permission dialog will still appear).
// https://chrismaddern.com/determine-whether-bluetooth-is-enabled-on-ios-passively/
// https://stackoverflow.com/a/58600900
private val options = mapOf<Any?, Any>(CBCentralManagerOptionShowPowerAlertKey to false)

private var cachedState: CBManagerState? = null
private val mutex = Mutex()

internal actual suspend fun isSupported() = mutex.withLock {
cachedState ?: awaitState().also { cachedState = it }
} != CBManagerStateUnsupported

// Need to hold strong-reference to CBCentralManager and its delegate while in use.
private var managerRef: NSObject? = null
private var delegateRef: NSObject? = null

private suspend fun awaitState() = callbackFlow {
val delegate = object : NSObject(), CBCentralManagerDelegateProtocol {
override fun centralManagerDidUpdateState(central: CBCentralManager) {
trySend(central.state).onFailure {
// Silently ignore.
}
}
}

delegateRef = delegate
managerRef = CBCentralManager(delegate, null, options)

awaitClose {
managerRef = null
delegateRef = null
}
}.first { it.isDetermined }

private val CBManagerState.isDetermined: Boolean
get() = this != CBManagerStateUnknown && this != CBManagerStateResetting
internal actual suspend fun isSupported() = true
8 changes: 6 additions & 2 deletions kable-core/src/commonMain/kotlin/Bluetooth.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -35,16 +35,20 @@ public object Bluetooth {
public data class Unavailable(val reason: Reason?) : Availability()
}

public val availability: Flow<Availability> = bluetoothAvailability

/**
* Checks if Bluetooth Low Energy is supported on the system. Being supported (a return of
* `true`) does not necessarily mean that bluetooth operations will work. The radio could be off
* or permissions may be denied.
*
* Due to Core Bluetooth limitations (unavoidable dialog upon checking if supported), this
* function **always** returns `true` on Apple (even if Bluetooth is not supported).
*
* This function is idempotent.
*/
@ExperimentalApi // Due to the inability to query Bluetooth support w/o showing a dialog on Apple, this function may be removed.
public suspend fun isSupported(): Boolean = isBluetoothSupported()

public val availability: Flow<Availability> = bluetoothAvailability
}

internal expect val bluetoothAvailability: Flow<Bluetooth.Availability>