Create `EventNotifier` helper class

1 files changed, 42 insertions, 0 deletions

diff --git a/android/src/main/kotlin/net/mullvad/mullvadvpn/util/EventNotifier.kt b/android/src/main/kotlin/net/mullvad/mullvadvpn/util/EventNotifier.kt
new file mode 100644
index 0000000000..ca45ca96e6
--- /dev/null
+++ b/android/src/main/kotlin/net/mullvad/mullvadvpn/util/EventNotifier.kt
@@ -0,0 +1,42 @@
+package net.mullvad.mullvadvpn.util
+
+class EventNotifier<T>(private val initialValue: T) {
+    private val listeners = HashMap<Int, (T) -> Unit>()
+
+    private var idCounter = 0
+    private var latestEvent = initialValue
+
+    fun notify(event: T) {
+        synchronized(this) {
+            for (listener in listeners.values) {
+                listener(event)
+            }
+
+            latestEvent = event
+        }
+    }
+
+    fun subscribe(listener: (T) -> Unit): Int {
+        synchronized(this) {
+            val id = idCounter
+
+            idCounter += 1
+            listeners.put(id, listener)
+            listener(latestEvent)
+
+            return id
+        }
+    }
+
+    fun unsubscribe(id: Int) {
+        synchronized(this) {
+            listeners.remove(id)
+        }
+    }
+
+    fun unsubscribeAll() {
+        synchronized(this) {
+            listeners.clear()
+        }
+    }
+}