Less backups (#2995)

* Add delta to FieldChangedEvents

* Do batched backups

* Turn the delta final

* Revert "Turn the delta final"

This reverts commit 0ca07d2.

* Fix checkstyle warnings

* One more try for fixing checkstyle

src/main/java/org/jabref/logic/autosaveandbackup/BackupManager.java

@@ -22,6 +22,7 @@
 import org.jabref.logic.util.io.FileUtil;
 import org.jabref.model.database.BibDatabaseContext;
 import org.jabref.model.database.event.BibDatabaseContextChangedEvent;
+import org.jabref.model.entry.event.FieldChangedEvent;
 import org.jabref.preferences.JabRefPreferences;
 
 import com.google.common.eventbus.Subscribe;
@@ -40,14 +41,17 @@ public class BackupManager {
 
     private static final String BACKUP_EXTENSION = ".sav";
 
+    private static final int MINOR_CHANGES_LIMIT = 5;
+
     private static Set<BackupManager> runningInstances = new HashSet<>();
 
+    private int minorChangesCount = 0;
+
     private final BibDatabaseContext bibDatabaseContext;
     private final JabRefPreferences preferences;
     private final ExecutorService executor;
     private final Runnable backupTask = () -> determineBackupPath().ifPresent(this::performBackup);
 
-
     private BackupManager(BibDatabaseContext bibDatabaseContext) {
         this.bibDatabaseContext = bibDatabaseContext;
         this.preferences = JabRefPreferences.getInstance();
@@ -129,7 +133,18 @@ private void performBackup(Path backupPath) {
 
     @Subscribe
     public synchronized void listen(@SuppressWarnings("unused") BibDatabaseContextChangedEvent event) {
-        startBackupTask();
+        if (!(event instanceof FieldChangedEvent)) {
+            startBackupTask();
+        } else {
+            // only do a backup if the field changes are more than one character or if there are enough of them
+            FieldChangedEvent fieldChange = (FieldChangedEvent) event;
+            if (fieldChange.getDelta() > 1 || minorChangesCount >= MINOR_CHANGES_LIMIT) {
+                startBackupTask();
+                minorChangesCount = 0;
+            } else {
+                minorChangesCount++;
+            }
+        }
     }
 
     private void startBackupTask() {

src/main/java/org/jabref/model/entry/event/FieldChangedEvent.java

@@ -11,52 +11,68 @@ public class FieldChangedEvent extends EntryChangedEvent {
     private final String fieldName;
     private final String newValue;
     private final String oldValue;
+    private int delta = 0;
 
 
     /**
-     * @param bibEntry Affected BibEntry object
+     * @param bibEntry  Affected BibEntry object
      * @param fieldName Name of field which has been changed
-     * @param newValue new field value
-     * @param newValue old field value
-     * @param location location Location affected by this event
+     * @param newValue  new field value
+     * @param newValue  old field value
+     * @param location  location Location affected by this event
      */
     public FieldChangedEvent(BibEntry bibEntry, String fieldName, String newValue, String oldValue,
-            EntryEventSource location) {
+                             EntryEventSource location) {
         super(bibEntry, location);
         this.fieldName = fieldName;
         this.newValue = newValue;
         this.oldValue = oldValue;
+        delta = computeDelta(oldValue, newValue);
     }
 
     /**
-     * @param bibEntry Affected BibEntry object
+     * @param bibEntry  Affected BibEntry object
      * @param fieldName Name of field which has been changed
-     * @param newValue new field value
+     * @param newValue  new field value
      */
     public FieldChangedEvent(BibEntry bibEntry, String fieldName, String newValue, String oldValue) {
         super(bibEntry);
         this.fieldName = fieldName;
         this.newValue = newValue;
         this.oldValue = oldValue;
+        delta = computeDelta(oldValue, newValue);
     }
 
     /**
-     * @param bibEntry Affected BibEntry object
+     * @param bibEntry  Affected BibEntry object
      * @param fieldName Name of field which has been changed
-     * @param newValue new field value
-     * @param location location Location affected by this event
+     * @param newValue  new field value
+     * @param location  location Location affected by this event
      */
     public FieldChangedEvent(FieldChange fieldChange, EntryEventSource location) {
         super(fieldChange.getEntry(), location);
         this.fieldName = fieldChange.getField();
         this.newValue = fieldChange.getNewValue();
         this.oldValue = fieldChange.getOldValue();
+        delta = computeDelta(oldValue, newValue);
     }
 
     public FieldChangedEvent(FieldChange fieldChange) {
         this(fieldChange, EntryEventSource.LOCAL);
     }
 
+    private int computeDelta(String oldValue, String newValue) {
+        if (oldValue == newValue) {
+            return 0;
+        } else if (oldValue == null && newValue != null) {
+            return newValue.length();
+        } else if (newValue == null && oldValue != null) {
+            return oldValue.length();
+        } else {
+            return Math.abs(newValue.length() - oldValue.length());
+        }
+    }
+
     public String getFieldName() {
         return fieldName;
     }
@@ -69,4 +85,8 @@ public String getOldValue() {
         return oldValue;
     }
 
+    public int getDelta() {
+        return delta;
+    }
+
 }