1 files changed, 97 insertions, 0 deletions
diff --git a/app/src/main/java/com/wireguard/android/util/Topic.java b/app/src/main/java/com/wireguard/android/util/Topic.java
new file mode 100644
index 00000000..eed13c9e
--- /dev/null
+++ b/app/src/main/java/com/wireguard/android/util/Topic.java
@@ -0,0 +1,97 @@
+/*
+ * Copyright © 2017 John Wu <topjohnwu@gmail.com>
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+package com.wireguard.android.util;
+
+import java.lang.ref.WeakReference;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+
+public class Topic {
+
+    private static final int NON_INIT = 0;
+    private static final int PENDING = 1;
+    private static final int PUBLISHED = 2;
+
+    private int state = NON_INIT;
+    private List<WeakReference<Subscriber>> subscribers;
+    private Object[] results;
+
+    public void subscribe(Subscriber sub) {
+        if (subscribers == null) {
+            subscribers = new LinkedList<>();
+        }
+        subscribers.add(new WeakReference<>(sub));
+    }
+
+    public void unsubscribe() {
+        subscribers = null;
+    }
+
+    public void unsubscribe(Subscriber sub) {
+        for (Iterator<WeakReference<Subscriber>> i = subscribers.iterator(); i.hasNext();) {
+            WeakReference<Subscriber> subscriber = i.next();
+            if (subscriber.get() == null || subscriber.get() == sub) {
+                i.remove();
+            }
+        }
+    }
+
+    public void reset() {
+        state = NON_INIT;
+        results = null;
+    }
+
+    public boolean isPublished() {
+        return state == PUBLISHED;
+    }
+
+    public void publish() {
+        publish(true);
+    }
+
+    public void publish(boolean record, Object... results) {
+        if (record)
+            state = PUBLISHED;
+        this.results = results;
+        if (subscribers != null) {
+            for (WeakReference<Subscriber> subscriber : subscribers) {
+                if (subscriber.get() != null)
+                    subscriber.get().onTopicPublished(this);
+            }
+        }
+    }
+
+    public Object[] getResults() {
+        return results;
+    }
+
+    public boolean isPending() {
+        return state == PENDING;
+    }
+
+    public void setPending() {
+        state = PENDING;
+    }
+
+    public interface Subscriber {
+        default void subscribeTopics() {
+            for (Topic topic : getSubscription()) {
+                if (topic.isPublished()) {
+                    onTopicPublished(topic);
+                }
+                topic.subscribe(this);
+            }
+        }
+        default void unsubscribeTopics() {
+            for (Topic event : getSubscription()) {
+                event.unsubscribe(this);
+            }
+        }
+        void onTopicPublished(Topic topic);
+        Topic[] getSubscription();
+    }
+}