feat(edit): conflict dialog on save + store metadata refresh (v2.0)

No locking (plan 03, decision 5): openForEdit keeps an EditSnapshot — the
prefilled form plus the raw Events-row times, which the form itself can't
see (it derives its times from the tapped occurrence, so an externally
moved event would otherwise stay invisible). Right before writing,
performSave re-reads the event and compares snapshots: a mismatch parks
the save in SaveUiState.AwaitingConflict carrying the already-chosen
recurring scope, and the dialog offers overwrite / discard / cancel
(OptionCard style). Overwrite still writes only dirty fields, so external
changes to untouched fields survive either way. A deleted event lands in
SaveUiState.Gone — an informational dialog that closes form and detail.
Fields the form can't write (attendees, status, self response, reminder
methods) are excluded from the comparison so sync noise can't fake a
conflict. The load-time zone is pinned in the EditTarget so a device
timezone change mid-edit can't either.

Store metadata: F-Droid descriptions (DE+EN) and the README stop claiming
read-only and now describe write support and reminder delivery. New
fastlane phoneScreenshots (6 per locale: week/month/day/detail/form/
reminder onboarding), captured on-device against demo-only calendars.

Tests: EditSnapshot equality (unchanged event, field change, row-time move
the form can't see, non-writable changes stay quiet).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/main/java/de/jeanlucmakiola/calendula/domain/EventForm.kt

@@ -94,6 +94,30 @@ fun EventDetail.toEditForm(beginMillis: Long, endMillis: Long, zone: TimeZone):
     )
 }
 
+/**
+ * What the edit form saw when it loaded — compared against a fresh read at
+ * save time to detect external changes (sync, another device) that landed
+ * while the form was open. The raw row times ride along because
+ * [toEditForm] derives the form's times from the *tapped occurrence*, so
+ * re-deriving with the same occurrence would mask an externally moved
+ * event. Not covered (the form can't write them, and the dirty-checked
+ * write can't clobber them): attendees, status, the user's own response,
+ * reminder methods, and a recurring event's duration.
+ */
+data class EditSnapshot(
+    val form: EventForm,
+    /** The raw Events-row times (for recurring events: the series anchor). */
+    val rowStart: Instant,
+    val rowEnd: Instant,
+)
+
+fun EventDetail.toEditSnapshot(beginMillis: Long, endMillis: Long, zone: TimeZone): EditSnapshot =
+    EditSnapshot(
+        form = toEditForm(beginMillis, endMillis, zone),
+        rowStart = instance.start,
+        rowEnd = instance.end,
+    )
+
 /**
  * The optional sections that hold a value in [form] — when editing, these
  * must be visible regardless of the user's default-fields setting, or the

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditScreen.kt

@@ -217,7 +217,8 @@ fun EventEditScreen(
                 viewModel.consumeSaveResult()
                 snackbarHostState.showSnackbar(writeDeniedMessage)
             }
-            SaveUiState.Idle, SaveUiState.AwaitingScope, SaveUiState.Saving, null -> Unit
+            // AwaitingScope/AwaitingConflict/Gone render as dialogs below.
+            else -> Unit
         }
     }
 
@@ -269,6 +270,68 @@ fun EventEditScreen(
             onDismiss = viewModel::consumeSaveResult,
         )
     }
+
+    // The event changed externally (sync) while the form was open (v2.0).
+    if (state?.saveState is SaveUiState.AwaitingConflict) {
+        SaveConflictDialog(
+            onOverwrite = viewModel::saveOverwriting,
+            onDiscard = close,
+            onDismiss = viewModel::consumeSaveResult,
+        )
+    }
+
+    // ...or was deleted underneath us — nothing left to save onto. Closing
+    // through [onSaved] also pops the detail screen, whose occurrence is gone.
+    if (state?.saveState == SaveUiState.Gone) {
+        AlertDialog(
+            onDismissRequest = {},
+            title = { Text(stringResource(R.string.event_edit_gone_title)) },
+            text = { Text(stringResource(R.string.event_edit_gone_body)) },
+            confirmButton = {
+                TextButton(onClick = {
+                    viewModel.reset()
+                    onSaved()
+                }) { Text(stringResource(R.string.dialog_ok)) }
+            },
+        )
+    }
+}
+
+/**
+ * Overwrite-or-discard choice when the event changed underneath an open
+ * form (no locking; detected by re-reading at save time). "Overwrite" still
+ * only writes the fields the user edited — external changes to untouched
+ * fields survive either way. Cancelling returns to the form.
+ */
+@Composable
+private fun SaveConflictDialog(
+    onOverwrite: () -> Unit,
+    onDiscard: () -> Unit,
+    onDismiss: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.event_edit_conflict_title)) },
+        text = {
+            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
+                Text(stringResource(R.string.event_edit_conflict_body))
+                Spacer(Modifier.height(4.dp))
+                OptionCard(
+                    label = stringResource(R.string.event_edit_conflict_overwrite),
+                    supportingText = stringResource(R.string.event_edit_conflict_overwrite_hint),
+                    onClick = onOverwrite,
+                )
+                OptionCard(
+                    label = stringResource(R.string.event_edit_conflict_discard),
+                    supportingText = stringResource(R.string.event_edit_conflict_discard_hint),
+                    onClick = onDiscard,
+                )
+            }
+        },
+        confirmButton = {
+            TextButton(onClick = onDismiss) { Text(stringResource(R.string.dialog_cancel)) }
+        },
+    )
 }
 
 /**

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditUiState.kt

@@ -4,6 +4,7 @@ import de.jeanlucmakiola.calendula.domain.CalendarSource
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventFormField
 import de.jeanlucmakiola.calendula.domain.EventFormProblem
+import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
 
 /**
  * UI state for the event form (v1.2: create; v1.3 reuses it for edit). Null
@@ -39,6 +40,14 @@ sealed interface SaveUiState {
     data object Idle : SaveUiState
     /** A dirty recurring event waits for the user to pick the write scope. */
     data object AwaitingScope : SaveUiState
+    /**
+     * The event changed externally (sync) while the form was open; the save
+     * is parked with its chosen [scope] until the user picks overwrite,
+     * discard, or cancel.
+     */
+    data class AwaitingConflict(val scope: RecurringWriteScope) : SaveUiState
+    /** The event was deleted externally while the form was open. */
+    data object Gone : SaveUiState
     data object Saving : SaveUiState
     data object Saved : SaveUiState
     /** WRITE_CALENDAR was revoked between the tap and the provider call. */

app/src/main/java/de/jeanlucmakiola/calendula/ui/edit/EventEditViewModel.kt

@@ -4,18 +4,20 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
 import de.jeanlucmakiola.calendula.data.calendar.CalendarRepository
+import de.jeanlucmakiola.calendula.data.calendar.NoSuchEventException
 import de.jeanlucmakiola.calendula.data.di.IoDispatcher
 import de.jeanlucmakiola.calendula.data.prefs.CalendarPrefs
 import de.jeanlucmakiola.calendula.data.prefs.SettingsPrefs
 import de.jeanlucmakiola.calendula.domain.AccessLevel
 import de.jeanlucmakiola.calendula.domain.Availability
 import de.jeanlucmakiola.calendula.domain.CalendarSource
+import de.jeanlucmakiola.calendula.domain.EditSnapshot
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventFormField
 import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
 import de.jeanlucmakiola.calendula.domain.populatedFields
 import de.jeanlucmakiola.calendula.domain.problems
-import de.jeanlucmakiola.calendula.domain.toEditForm
+import de.jeanlucmakiola.calendula.domain.toEditSnapshot
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
@@ -68,15 +70,21 @@ class EventEditViewModel @Inject constructor(
     val loadFailed: StateFlow<Boolean> = _loadFailed.asStateFlow()
 
     /**
-     * The event being edited plus the form exactly as it was prefilled.
+     * The event being edited plus everything the form saw at load time.
      * For recurring events the write scope is chosen at save time; the
-     * tapped occurrence's [beginMillis] anchors occurrence-level writes.
+     * tapped occurrence's [beginMillis]/[endMillis] anchor occurrence-level
+     * writes and the conflict re-read. [zone] is pinned at load so a device
+     * timezone change mid-edit can't fake a conflict.
      */
     private data class EditTarget(
         val eventId: Long,
-        val original: EventForm,
+        val snapshot: EditSnapshot,
         val beginMillis: Long,
-    )
+        val endMillis: Long,
+        val zone: TimeZone,
+    ) {
+        val original: EventForm get() = snapshot.form
+    }
 
     private data class LocalInputs(
         val form: EventForm?,
@@ -167,11 +175,12 @@ class EventEditViewModel @Inject constructor(
                 _loadFailed.value = true
                 return@launch
             }
-            val original = detail.toEditForm(beginMillis, endMillis, TimeZone.currentSystemDefault())
-            _editTarget.value = EditTarget(eventId, original, beginMillis)
+            val zone = TimeZone.currentSystemDefault()
+            val snapshot = detail.toEditSnapshot(beginMillis, endMillis, zone)
+            _editTarget.value = EditTarget(eventId, snapshot, beginMillis, endMillis, zone)
             // Sections holding data must show even when not in the defaults.
-            _revealed.value = original.populatedFields()
-            _form.value = original
+            _revealed.value = snapshot.form.populatedFields()
+            _form.value = snapshot.form
         }
     }
 
@@ -249,10 +258,43 @@ class EventEditViewModel @Inject constructor(
         performSave(current.form, scope)
     }
 
-    private fun performSave(form: EventForm, scope: RecurringWriteScope) {
+    /** Finish a save parked in [SaveUiState.AwaitingConflict], overwriting. */
+    fun saveOverwriting() {
+        val current = state.value ?: return
+        val parked = current.saveState as? SaveUiState.AwaitingConflict ?: return
+        performSave(current.form, parked.scope, ignoreConflict = true)
+    }
+
+    private fun performSave(
+        form: EventForm,
+        scope: RecurringWriteScope,
+        ignoreConflict: Boolean = false,
+    ) {
         val target = _editTarget.value
         viewModelScope.launch {
             _saveState.value = SaveUiState.Saving
+            // No locking (plan 03, decision 5): right before writing, re-read
+            // the event and compare against what the form loaded. An external
+            // change parks the save in a conflict dialog instead of silently
+            // clobbering the edited fields.
+            if (target != null && !ignoreConflict) {
+                val fresh = try {
+                    repository.eventDetail(target.eventId)
+                        .toEditSnapshot(target.beginMillis, target.endMillis, target.zone)
+                } catch (e: CancellationException) {
+                    throw e
+                } catch (e: NoSuchEventException) {
+                    _saveState.value = SaveUiState.Gone
+                    return@launch
+                } catch (e: Exception) {
+                    // Can't verify — proceed; a real problem fails the write itself.
+                    null
+                }
+                if (fresh != null && fresh != target.snapshot) {
+                    _saveState.value = SaveUiState.AwaitingConflict(scope)
+                    return@launch
+                }
+            }
             _saveState.value = try {
                 if (target == null) {
                     repository.createEvent(form)

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

@@ -82,6 +82,16 @@
     <string name="event_edit_availability">Verfügbarkeit</string>
     <string name="event_edit_visibility">Sichtbarkeit</string>
 
+    <!-- Termin-Formular — Speicher-Konflikt (v2.0) -->
+    <string name="event_edit_conflict_title">Termin wurde extern geändert</string>
+    <string name="event_edit_conflict_body">Während du bearbeitet hast, wurde dieser Termin anderswo geändert — durch Synchronisierung oder eine andere App. Was soll mit deinen Änderungen passieren?</string>
+    <string name="event_edit_conflict_overwrite">Meine Änderungen speichern</string>
+    <string name="event_edit_conflict_overwrite_hint">Nur von dir bearbeitete Felder überschreiben die externe Änderung</string>
+    <string name="event_edit_conflict_discard">Meine Änderungen verwerfen</string>
+    <string name="event_edit_conflict_discard_hint">Der Termin bleibt, wie er jetzt ist</string>
+    <string name="event_edit_gone_title">Termin wurde gelöscht</string>
+    <string name="event_edit_gone_body">Dieser Termin wurde zwischenzeitlich gelöscht, etwa auf einem anderen Gerät. Deine Änderungen können nicht mehr gespeichert werden.</string>
+
     <!-- Termin-Formular — Wiederholungs-Picker (v1.3) -->
     <string name="event_edit_recurrence_none">Wiederholt sich nicht</string>
     <string name="event_edit_recurrence_custom">Benutzerdefiniert</string>

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

@@ -83,6 +83,16 @@
     <string name="event_edit_availability">Availability</string>
     <string name="event_edit_visibility">Visibility</string>
 
+    <!-- Event form — save conflict (v2.0) -->
+    <string name="event_edit_conflict_title">Event changed elsewhere</string>
+    <string name="event_edit_conflict_body">While you were editing, this event was changed — by sync or another app. What should happen to your changes?</string>
+    <string name="event_edit_conflict_overwrite">Save my changes</string>
+    <string name="event_edit_conflict_overwrite_hint">Only fields you edited overwrite the outside change</string>
+    <string name="event_edit_conflict_discard">Discard my changes</string>
+    <string name="event_edit_conflict_discard_hint">The event stays as it is now</string>
+    <string name="event_edit_gone_title">Event deleted</string>
+    <string name="event_edit_gone_body">This event was deleted in the meantime, for example on another device. Your changes can no longer be saved.</string>
+
     <!-- Event form — recurrence picker (v1.3) -->
     <string name="event_edit_recurrence_none">Does not repeat</string>
     <string name="event_edit_recurrence_custom">Custom</string>