feat: enhance subscription logic to support wildcard checks and improve unsubscribe handling

cloud-sdk/src/main/java/com/dji/sdk/mqtt/MqttTopicServiceImpl.java

@@ -28,8 +28,8 @@ public class MqttTopicServiceImpl implements IMqttTopicService {
     public void subscribe(String... topics) {
         Set<String> topicSet = new HashSet<>(Arrays.asList(getSubscribedTopic()));
         for (String topic : topics) {
-            if (topicSet.contains(topic)) {
-                return;
+            if (topicSet.contains(topic) || isCoveredByWildcard(topicSet, topic)) {
+                continue;
             }
             subscribe(topic, 1);
         }
@@ -38,7 +38,7 @@ public class MqttTopicServiceImpl implements IMqttTopicService {
     @Override
     public void subscribe(String topic, int qos) {
         Set<String> topicSet = new HashSet<>(Arrays.asList(getSubscribedTopic()));
-        if (topicSet.contains(topic)) {
+        if (topicSet.contains(topic) || isCoveredByWildcard(topicSet, topic)) {
             return;
         }
         log.debug("subscribe topic: {}", topic);
@@ -47,11 +47,41 @@ public class MqttTopicServiceImpl implements IMqttTopicService {
 
     @Override
     public void unsubscribe(String... topics) {
-        log.debug("unsubscribe topic: {}", Arrays.toString(topics));
-        adapter.removeTopic(topics);
+        Set<String> currentTopics = new HashSet<>(Arrays.asList(getSubscribedTopic()));
+        for (String topic : topics) {
+            if (!currentTopics.contains(topic)) {
+                continue;
+            }
+            if (isCoveredByWildcard(currentTopics, topic)) {
+                log.debug("skip unsubscribe, topic {} is covered by wildcard", topic);
+                continue;
+            }
+            log.debug("unsubscribe topic: {}", topic);
+            adapter.removeTopic(topic);
+        }
     }
 
     public String[] getSubscribedTopic() {
         return adapter.getTopic();
     }
+
+    /**
+     * Check if a specific topic is already covered by a single-level wildcard (+) subscription.
+     * e.g. "thing/product/DRONE-001/osd" is covered by "thing/product/+/osd"
+     */
+    private boolean isCoveredByWildcard(Set<String> existingTopics, String topic) {
+        String[] parts = topic.split("/");
+        if (parts.length < 3) {
+            return false;
+        }
+        for (int i = 0; i < parts.length; i++) {
+            String[] wildcardParts = parts.clone();
+            wildcardParts[i] = "+";
+            String wildcardTopic = String.join("/", wildcardParts);
+            if (existingTopics.contains(wildcardTopic)) {
+                return true;
+            }
+        }
+        return false;
+    }
 }