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@@ -34,6 +34,7 @@ kotlin { | |
| dependencies { | ||
| api(coroutines()) | ||
| api(uuid()) | ||
| implementation(tuulbox("collections")) | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,100 @@ | ||
| package com.juul.kable | ||
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| import com.juul.kable.State.Connected | ||
| import com.juul.kable.logs.Logger | ||
| import com.juul.kable.logs.Logging | ||
| import kotlinx.atomicfu.atomic | ||
| import kotlinx.coroutines.flow.StateFlow | ||
| import kotlinx.coroutines.sync.Mutex | ||
| import kotlinx.coroutines.sync.withLock | ||
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| internal class Observation( | ||
| private val state: StateFlow<State>, | ||
| private val handler: Handler, | ||
| private val characteristic: Characteristic, | ||
| logging: Logging, | ||
| identifier: String, | ||
| ) { | ||
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| interface Handler { | ||
| suspend fun startObservation(characteristic: Characteristic) | ||
| suspend fun stopObservation(characteristic: Characteristic) | ||
| } | ||
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| private val logger = Logger(logging, tag = "Kable/Observation", identifier) | ||
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| private val mutex = Mutex() | ||
| private val subscribers = mutableListOf<OnSubscriptionAction>() | ||
| private val isObservationEnabled = atomic(false) | ||
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| private val isConnected: Boolean | ||
| get() = state.value is Connected | ||
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| private val hasSubscribers: Boolean | ||
| get() = subscribers.isNotEmpty() | ||
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| suspend fun onSubscription(action: OnSubscriptionAction) = mutex.withLock { | ||
| subscribers += action | ||
| enableObservationIfNeeded() | ||
| if (isObservationEnabled.value) { | ||
| // Ignore `NotConnectedException` to guard against potential race-condition where disconnect occurs | ||
| // immediately after checking `isObservationEnabled`. | ||
| suppressNotConnectedException { | ||
| action() | ||
| } | ||
| } | ||
| } | ||
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| suspend fun onCompletion(action: OnSubscriptionAction) = mutex.withLock { | ||
| subscribers -= action | ||
| disableObservationIfNeeded() | ||
| } | ||
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| suspend fun onConnected() = mutex.withLock { | ||
| enableObservationIfNeeded() | ||
| if (isObservationEnabled.value) { | ||
| // Ignore `NotConnectedException` to guard against potential race-condition where disconnect occurs | ||
| // immediately after checking `isObservationEnabled`. | ||
| suppressNotConnectedException { | ||
| subscribers.forEach { it() } | ||
| } | ||
| } | ||
| } | ||
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| fun onConnectionLost() { | ||
| // We assume that remote peripheral and local BLE system implicitly clears notifications/indications. | ||
| isObservationEnabled.value = false | ||
| } | ||
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| private suspend fun enableObservationIfNeeded() { | ||
| if (!isObservationEnabled.value && isConnected && hasSubscribers) { | ||
| suppressNotConnectedException { | ||
| handler.startObservation(characteristic) | ||
| isObservationEnabled.value = true | ||
| } | ||
| } | ||
| } | ||
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| private suspend fun disableObservationIfNeeded() { | ||
| if (isObservationEnabled.value && isConnected && !hasSubscribers) { | ||
| suppressNotConnectedException { | ||
| handler.stopObservation(characteristic) | ||
| } | ||
| isObservationEnabled.value = false | ||
| } | ||
| } | ||
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| /** | ||
| * It is assumed that observations are automatically cleared on disconnect, therefore in some situations | ||
| * [NotConnectedException]s can be ignored, as the corresponding [action] will be rendered unnecessary | ||
| * (e.g. clearing an observation is not needed if connection has been lost), or [action] will be re-attempted on | ||
| * [reconnect][onConnected]. | ||
| */ | ||
| private inline fun suppressNotConnectedException(action: () -> Unit) { | ||
| try { | ||
| action.invoke() | ||
| } catch (e: NotConnectedException) { | ||
| logger.verbose { message = "Suppressed failure: ${e.message}" } | ||
| } | ||
| } | ||
| } |