Add sort by most recent tracker detection (#537)

* Add option in menu page to sort in order of app last detected with tracking

* Resolve naming issue for sorting apps with recent trackers detected, fix tiebreaking so that it is done in alphabetical order if both apps have the same last tracker detected time

* Improve readability, add comments

Author: nmarteybotchway

app/src/main/java/eu/faircode/netguard/ActivityMain.java

@@ -933,6 +933,8 @@ else if ("name".equals(sort))
             menu.findItem(R.id.menu_sort_name).setChecked(true);
         else if ("trackers_all".equals(sort))
             menu.findItem(R.id.menu_sort_trackers_all).setChecked(true);
+        else if ("trackers_recent".equals(sort))
+            menu.findItem(R.id.menu_sort_by_latest_detected_tracker).setChecked(true);
         else
             menu.findItem(R.id.menu_sort_trackers_week).setChecked(true);
 
@@ -974,6 +976,10 @@ public boolean onOptionsItemSelected(MenuItem item) {
             item.setChecked(true);
             prefs.edit().putString("sort", "trackers_all").apply();
             return true;
+        } else if (itemId == R.id.menu_sort_by_latest_detected_tracker) {
+            item.setChecked(true);
+            prefs.edit().putString("sort", "trackers_recent").apply();
+            return true;
         } else if (itemId == R.id.menu_sort_uid) {
             item.setChecked(true);
             prefs.edit().putString("sort", "uid").apply();

app/src/main/java/eu/faircode/netguard/Rule.java

@@ -99,7 +99,12 @@ public class Rule {
     private static Map<String, Boolean> cacheSystem = new HashMap<>();
     private static Map<String, Boolean> cacheInternet = new HashMap<>();
     private static Map<PackageInfo, Boolean> cacheEnabled = new HashMap<>();
+    private static Map<Integer, Long> trackerRecent = new HashMap<>();
 
+    public long getLastTrackerTime() {
+        Long time = trackerRecent.get(uid);
+        return time == null ? 0L : time;
+    }
     static List<PackageInfo> getPackages(Context context) {
         if (cachePackageInfo == null) {
             PackageManager pm = context.getPackageManager();
@@ -455,6 +460,7 @@ public static List<Rule> getRules(final boolean all, boolean self, Context conte
 
             trackerCounts = trackerCountsAndTotalAll.first();
             trackerCountsPastWeek = trackerCountsAndTotalPastWeek.first();
+            trackerRecent = trackerList.getLastTrackerTimes();
             int trackerTotal = trackerCountsAndTotalAll.second();
 
             if (trackerTotal == 0
@@ -500,6 +506,17 @@ public int compare(Rule rule, Rule other) {
                         return (rule.changed ? -1 : 1);
                     }
                 });
+            else if ("trackers_recent".equals(sort)) {
+                Collections.sort(listRules, (a, b) -> {
+                    // Most recent tracker contact first
+                    int timeCmp = Long.compare(b.getLastTrackerTime(), a.getLastTrackerTime());
+                    if (timeCmp != 0) return timeCmp;
+
+                    // Tiebreak: alphabetical by app name, then package name
+                    int nameCmp = collator.compare(a.name, b.name);
+                    return nameCmp != 0 ? nameCmp : a.packageName.compareTo(b.packageName);
+                });
+            }
             else
                 Collections.sort(listRules, new Comparator<Rule>() {
                     @Override

app/src/main/java/net/kollnig/missioncontrol/data/TrackerList.java

@@ -258,6 +258,38 @@ private Pair<Map<Integer, Integer>, Integer> countTrackers(Map<Integer, Set<Stri
         return new Pair<>(trackerCounts, totalTracker);
     }
 
+    /**
+     * Iterate through all recorded host contacts and identify those that belong to known trackers,
+     * For each app, only the most recent tracker contact time is stored in the hashmap. Used to
+     * sort by most recent tracker detection in the main app list.
+     *
+     * @return A map of app UIDs to their most recent tracker contact timestamp in milliseconds
+     * since epoch. Apps with no tracker contacts are not included in the map.
+     */
+    public synchronized Map<Integer, Long> getLastTrackerTimes() {
+        Map<Integer, Long> result = new HashMap<>();
+
+        try (Cursor cursor = databaseHelper.getHosts()) {
+            if (cursor.moveToFirst()) {
+                do {
+                    int uid = cursor.getInt(cursor.getColumnIndexOrThrow("uid"));
+                    String hostname = cursor.getString(cursor.getColumnIndexOrThrow("daddr"));
+                    long time = cursor.getLong(cursor.getColumnIndexOrThrow("time"));
+
+                    Tracker tracker = findTracker(hostname);
+                    if (tracker == null)
+                        continue;
+
+                    Long existing = result.get(uid);
+                    if (existing == null || time > existing)
+                        result.put(uid, time);
+
+                } while (cursor.moveToNext());
+            }
+        }
+
+        return result;
+    }
     /**
      * Retrieve info for CSV export
      *

app/src/main/res/menu/main.xml

@@ -43,6 +43,9 @@
                 <item
                     android:id="@+id/menu_sort_name"
                     android:title="@string/menu_sort_name"/>
+                <item
+                    android:id="@+id/menu_sort_by_latest_detected_tracker"
+                    android:title="@string/menu_sort_by_latest_detected_tracker"/>
                 <item
                     android:visible="false"
                     android:id="@+id/menu_sort_uid"

app/src/main/res/values/strings.xml

@@ -21,6 +21,7 @@
     <string name="menu_sort_uid">Sort by uid</string>
     <string name="menu_sort_companies_week">Sort by companies (week)</string>
     <string name="menu_sort_companies">Sort by companies</string>
+    <string name="menu_sort_by_latest_detected_tracker">Sort by latest detected tracker</string>
     <string name="menu_log">Traffic log</string>
     <string name="menu_settings">Settings</string>
     <string name="menu_invite">Invite</string>