Create `HandlerFlow` helper type

A handler message loop that can be used as a `Flow`.

1 files changed, 45 insertions, 0 deletions

diff --git a/android/src/main/kotlin/net/mullvad/mullvadvpn/ipc/HandlerFlow.kt b/android/src/main/kotlin/net/mullvad/mullvadvpn/ipc/HandlerFlow.kt
new file mode 100644
index 0000000000..943c55eeff
--- /dev/null
+++ b/android/src/main/kotlin/net/mullvad/mullvadvpn/ipc/HandlerFlow.kt
@@ -0,0 +1,45 @@
+package net.mullvad.mullvadvpn.ipc
+
+import android.os.Handler
+import android.os.Looper
+import android.os.Message
+import android.util.Log
+import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.InternalCoroutinesApi
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.ClosedSendChannelException
+import kotlinx.coroutines.channels.sendBlocking
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.FlowCollector
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.flow.consumeAsFlow
+import kotlinx.coroutines.flow.onCompletion
+
+class HandlerFlow<T>(
+    looper: Looper,
+    private val extractor: (Message) -> T
+) : Handler(looper), Flow<T> {
+    private val channel = Channel<T>(Channel.UNLIMITED)
+    private val flow = channel.consumeAsFlow().onCompletion {
+        removeCallbacksAndMessages(null)
+    }
+
+    @InternalCoroutinesApi
+    override suspend fun collect(collector: FlowCollector<T>) = flow.collect(collector)
+
+    override fun handleMessage(message: Message) {
+        val extractedData = extractor(message)
+
+        try {
+            channel.sendBlocking(extractedData)
+        } catch (exception: Exception) {
+            when (exception) {
+                is ClosedSendChannelException, is CancellationException -> {
+                    Log.w("mullvad", "Received a message after HandlerFlow was closed", exception)
+                    removeCallbacksAndMessages(null)
+                }
+                else -> throw exception
+            }
+        }
+    }
+}