LinkScannerService: don't repeatedly scan

- have the system only send 10 events a second, instead of 1000
- don't scan the same package+class name more than once a second
- put each event view scanner on its own thread keyed by package+class
- don't scan if there is already an existing thread for the package+class

this can still cause high cpu usage on views with lots of text
especially if the user continually interacts with it
but is overall much better

to recap:
- a given package+class can only be scanned at most once a second
- a given package+class can only have one scanner at a time
- text to scan will not be scanned if already scanned
- domains to scan will not be scanned if already scanned

Signed-off-by: Tavi <tavi@divested.dev>

.idea/deploymentTargetSelector.xml

@@ -5,6 +5,9 @@
       <SelectionState runConfigName="app">
         <option name="selectionMode" value="DROPDOWN" />
       </SelectionState>
+      <SelectionState runConfigName="MainActivity">
+        <option name="selectionMode" value="DROPDOWN" />
+      </SelectionState>
     </selectionStates>
   </component>
 </project>

app/build.gradle

@@ -6,8 +6,8 @@ android {
         applicationId "us.spotco.malwarescanner"
         minSdkVersion 16
         targetSdkVersion 32
-        versionCode 311
-        versionName "3.11"
+        versionCode 312
+        versionName "3.12"
         resConfigs 'en', 'af', 'cs', 'de', 'el', 'es', 'fi', 'fr', 'gl', 'it', 'pl', 'pt', 'pt-rBR', 'ru', 'tr', 'zh-rCN'
     }
     buildTypes {

app/src/main/java/us/spotco/malwarescanner/LinkScannerService.java

@@ -10,6 +10,7 @@ import android.view.accessibility.AccessibilityEvent;
 import android.view.accessibility.AccessibilityNodeInfo;
 
 import java.util.Random;
+import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.ConcurrentSkipListSet;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -18,6 +19,9 @@ public class LinkScannerService extends AccessibilityService {
 
     private static final String hostnameRegex = "^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$"; //Credit: http://www.mkyong.com/regular-expressions/domain-name-regular-expression-example/
     private static final Pattern hostnamePattern = Pattern.compile(hostnameRegex);
+    private static final ConcurrentSkipListMap<String, Long> scannedPackages = new ConcurrentSkipListMap<>();
+    private static final ConcurrentSkipListMap<String, Thread> scannerThreads = new ConcurrentSkipListMap<>();
+
     private static final ConcurrentSkipListSet<Integer> scannedText = new ConcurrentSkipListSet<>();
     private static final ConcurrentSkipListSet<String> scannedDomains = new ConcurrentSkipListSet<>();
     private NotificationManager notificationManager = null;
@@ -35,7 +39,34 @@ public class LinkScannerService extends AccessibilityService {
     @Override
     public void onAccessibilityEvent(AccessibilityEvent event) {
         if (Database.isDomainDatabaseLoaded()) {
-            scanViews(event.getSource());
+            boolean shouldScanView = true;
+            String packageName = (String) event.getPackageName();
+            if (event.getSource() != null) {
+                packageName += event.getSource().getClassName();
+            }
+            if (scannedPackages.containsKey(packageName)) {
+                if ((System.currentTimeMillis() - scannedPackages.get(packageName)) < 1000) {
+                    shouldScanView = false;
+                }
+            }
+            if (shouldScanView) {
+                if (scannerThreads.containsKey(packageName)) {
+                    Thread oldThread = scannerThreads.get(packageName);
+                    if (oldThread != null) {
+                        if (oldThread.isAlive()) {
+                            shouldScanView = false;
+                        } else {
+                            scannerThreads.remove(packageName);
+                        }
+                    }
+                }
+            }
+            if (shouldScanView) {
+                scannedPackages.put(packageName, System.currentTimeMillis());
+                Thread thread = new Thread(() -> scanViews(event.getSource()));
+                scannerThreads.put(packageName, thread);
+                thread.start();
+            }
         }
     }
 

app/src/main/res/xml/accessibility_service_config.xml

@@ -4,5 +4,5 @@
     android:accessibilityEventTypes="typeWindowContentChanged|typeViewTextChanged"
     android:accessibilityFlags="flagDefault"
     android:accessibilityFeedbackType="feedbackGeneric"
-    android:notificationTimeout="1"
+    android:notificationTimeout="100"
     android:canRetrieveWindowContent="true" />

fastlane/metadata/android/en-US/changelogs/312.txt

@@ -0,0 +1 @@
+* Many optimizations to the link scanner feature