Fix timer edge cases: thread safety, duplicate dialogs, concurrent timers

- Remove background thread mutation of logbook.logs during merge to
  prevent ConcurrentModificationException crashes
- Cancel ongoing timer when user enters manual duration to prevent
  orphaned ongoing events
- Prevent duplicate timer dialogs when tapping ongoing event in list
- Block starting a second timer while another is already running
- Track old fingerprint on event edit to prevent merge re-adding
  the old version

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/main/java/it/danieleverducci/lunatracker/MainActivity.kt

@@ -334,6 +334,10 @@ class MainActivity : AppCompatActivity() {
             Toast.makeText(this, R.string.breastfeeding_timer_already_running, Toast.LENGTH_SHORT).show()
             return
         }
+        if (sleepTimerStartTime > 0) {
+            Toast.makeText(this, R.string.another_timer_already_running, Toast.LENGTH_SHORT).show()
+            return
+        }
 
         // Check logbook for existing ongoing breastfeeding event (from another device)
         val existingOngoing = logbook?.logs?.let { LunaEvent.findOngoingBreastfeeding(it) }
@@ -431,6 +435,11 @@ class MainActivity : AppCompatActivity() {
     }
 
     fun askBreastfeedingDuration(eventType: String) {
+        // Cancel any running timer to avoid orphaned ongoing events
+        if (bfTimerType != null) {
+            cancelBreastfeedingTimer()
+        }
+
         val d = AlertDialog.Builder(this)
         val dialogView = layoutInflater.inflate(R.layout.breastfeeding_duration_dialog, null)
         d.setTitle(R.string.breastfeeding_duration_title)
@@ -479,6 +488,10 @@ class MainActivity : AppCompatActivity() {
             Toast.makeText(this, R.string.sleep_timer_already_running, Toast.LENGTH_SHORT).show()
             return
         }
+        if (bfTimerType != null) {
+            Toast.makeText(this, R.string.another_timer_already_running, Toast.LENGTH_SHORT).show()
+            return
+        }
 
         // Check logbook for existing ongoing sleep event (from another device)
         val existingOngoing = logbook?.logs?.let { LunaEvent.findOngoing(it, LunaEvent.TYPE_SLEEP) }
@@ -576,6 +589,11 @@ class MainActivity : AppCompatActivity() {
     }
 
     fun askSleepDuration() {
+        // Cancel any running timer to avoid orphaned ongoing events
+        if (sleepTimerStartTime > 0) {
+            cancelSleepTimer()
+        }
+
         val d = AlertDialog.Builder(this)
         val dialogView = layoutInflater.inflate(R.layout.sleep_duration_dialog, null)
         d.setTitle(R.string.sleep_duration_title)
@@ -895,6 +913,7 @@ class MainActivity : AppCompatActivity() {
         // If event is ongoing, show the appropriate timer dialog instead
         if (event.ongoing) {
             if (event.type in LunaEvent.BREASTFEEDING_TYPES) {
+                if (bfTimerDialog?.isShowing == true) return
                 if (bfTimerType == null) {
                     bfTimerStartTime = event.time * 1000
                     bfTimerType = event.type
@@ -902,6 +921,7 @@ class MainActivity : AppCompatActivity() {
                 }
                 showBreastfeedingTimerDialog(event.type)
             } else if (event.type == LunaEvent.TYPE_SLEEP) {
+                if (sleepTimerDialog?.isShowing == true) return
                 if (sleepTimerStartTime == 0L) {
                     sleepTimerStartTime = event.time * 1000
                     saveSleepTimerState()
@@ -939,6 +959,8 @@ class MainActivity : AppCompatActivity() {
                 TimePickerDialog(this, { _, hour, minute ->
                     val pickedDateTime = Calendar.getInstance()
                     pickedDateTime.set(year, month, day, hour, minute)
+                    // Track old fingerprint so merge doesn't re-add the old version
+                    logbook?.removedSinceLoad?.add(event.fingerprint())
                     // Save event and move it to the right position in the logbook
                     event.time = pickedDateTime.time.time / 1000 // Seconds since epoch
                     dateTextView.text = String.format(getString(R.string.dialog_event_detail_datetime_icon), DateUtils.formatDateTime(event.time))
@@ -980,6 +1002,8 @@ class MainActivity : AppCompatActivity() {
                 pickerDialog.setPositiveButton(android.R.string.ok) { _, _ ->
                     val newQuantity = picker.value
                     if (newQuantity != oldQuantity) {
+                        // Track old fingerprint so merge doesn't re-add the old version
+                        logbook?.removedSinceLoad?.add(event.fingerprint())
                         // Adjust end time based on duration change (duration reduced = end time earlier)
                         event.time = event.time - (oldQuantity - newQuantity) * 60L
                         event.quantity = newQuantity
@@ -1475,10 +1499,6 @@ class MainActivity : AppCompatActivity() {
                 runOnUiThread({
                     setLoading(false)
 
-                    // Refresh list - merge may have added events from other devices
-                    logbook?.sort()
-                    recyclerView.adapter?.notifyDataSetChanged()
-
                     Toast.makeText(
                         this@MainActivity,
                         if (lastEventAdded != null)

app/src/main/java/it/danieleverducci/lunatracker/repository/WebDAVLogbookRepository.kt

@@ -133,14 +133,9 @@ class WebDAVLogbookRepository(val webDavURL: String, val username: String, val p
     }
 
     private fun saveLogbook(context: Context, logbook: Logbook) {
-        // Take a snapshot of local events to avoid thread safety issues
+        // Take a snapshot of local events (UI thread may modify logbook.logs concurrently)
-        // (UI thread may modify logbook.logs concurrently)
+        val localSnapshot = ArrayList(logbook.logs)
-        val localSnapshot: List<LunaEvent>
+        val removedFingerprints = HashSet(logbook.removedSinceLoad)
-        val removedFingerprints: Set<String>
-        synchronized(logbook.logs) {
-            localSnapshot = ArrayList(logbook.logs)
-            removedFingerprints = HashSet(logbook.removedSinceLoad)
-        }
 
         // Load remote logbook and merge before saving to avoid overwriting
         // events added by other devices
@@ -149,17 +144,9 @@ class WebDAVLogbookRepository(val webDavURL: String, val username: String, val p
             val remoteLogbook = loadLogbook(logbook.name)
             val added = mergeRemoteEvents(mergedEvents, remoteLogbook, removedFingerprints)
             if (added > 0) {
-                // Add merged events back to the actual logbook for UI display
-                synchronized(logbook.logs) {
-                    val currentFingerprints = logbook.logs.map { it.fingerprint() }.toHashSet()
-                    for (event in mergedEvents) {
-                        if (!currentFingerprints.contains(event.fingerprint())) {
-                            logbook.logs.add(event)
-                        }
-                    }
-                }
                 Log.d(TAG, "Merged $added remote events, saving ${mergedEvents.size} total")
             }
+            // Merged events will appear in UI on next periodic load (max 60s)
         } catch (e: Exception) {
             // Remote not available (404, network error, etc.) - save local version as-is
             Log.w(TAG, "Could not load remote logbook for merge: $e")

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

@@ -104,6 +104,7 @@
     <string name="breastfeeding_timer_stop">Stopp</string>
     <string name="breastfeeding_timer_hint">Tippe Stopp wenn fertig</string>
     <string name="breastfeeding_timer_already_running">Es läuft bereits eine Stillsitzung</string>
+    <string name="another_timer_already_running">Es läuft bereits ein anderer Timer</string>
     <string name="breastfeeding_duration_title">Stilldauer</string>
     <string name="breastfeeding_duration_description">Dauer in Minuten eingeben</string>
 

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

@@ -104,6 +104,7 @@
     <string name="breastfeeding_timer_stop">Arrêter</string>
     <string name="breastfeeding_timer_hint">Appuyez sur Arrêter quand terminé</string>
     <string name="breastfeeding_timer_already_running">Une session d\'allaitement est déjà en cours</string>
+    <string name="another_timer_already_running">Un autre minuteur est déjà en cours</string>
     <string name="breastfeeding_duration_title">Durée d\'allaitement</string>
     <string name="breastfeeding_duration_description">Entrez la durée en minutes</string>
 

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

@@ -104,6 +104,7 @@
     <string name="breastfeeding_timer_stop">Stop</string>
     <string name="breastfeeding_timer_hint">Premi Stop quando hai finito</string>
     <string name="breastfeeding_timer_already_running">Una sessione di allattamento è già in corso</string>
+    <string name="another_timer_already_running">Un altro timer è già in corso</string>
     <string name="breastfeeding_duration_title">Durata allattamento</string>
     <string name="breastfeeding_duration_description">Inserisci la durata in minuti</string>
 

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

@@ -162,6 +162,7 @@
     <string name="breastfeeding_timer_stop">Stop</string>
     <string name="breastfeeding_timer_hint">Tap Stop when finished</string>
     <string name="breastfeeding_timer_already_running">A breastfeeding session is already in progress</string>
+    <string name="another_timer_already_running">Another timer is already running</string>
     <string name="breastfeeding_duration_title">Breastfeeding duration</string>
     <string name="breastfeeding_duration_description">Enter the duration in minutes</string>
     <string name="measurement_unit_time_minutes" translatable="false">min</string>