app/src/main/java/de/jeanlucmakiola/calendula/ui/CalendarHost.kt

@@ -368,6 +368,14 @@ fun CalendarHost(
                         heldEditKey = key
                         editKey = key
                     },
+                    onDuplicate = { form ->
+                        // Reuse the prefilled-create overlay: a duplicate is a
+                        // fresh event, so it applies the default reminder like an
+                        // in-app new event (#52).
+                        importFormSource = ImportSource.Insert
+                        importForm = form
+                        detailKey = null
+                    },
                 )
             }
         }

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailScreen.kt

@@ -32,6 +32,7 @@ import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.filled.ArrowBack
 import androidx.compose.material.icons.automirrored.filled.Notes
 import androidx.compose.material.icons.filled.CalendarMonth
+import androidx.compose.material.icons.filled.ContentCopy
 import androidx.compose.material.icons.filled.Delete
 import androidx.compose.material.icons.filled.Edit
 import androidx.compose.material.icons.filled.Notifications
@@ -87,6 +88,7 @@ import de.jeanlucmakiola.calendula.domain.AttendeeRelationship
 import de.jeanlucmakiola.calendula.domain.AttendeeStatus
 import de.jeanlucmakiola.calendula.domain.AttendeeType
 import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.EventStatus
 import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
@@ -116,7 +118,10 @@ import kotlin.time.Instant
  * top-bar arrow both return to the calendar. Events in writable calendars can
  * be deleted (v1.1) and edited (v1.3) from here; [onEdit] opens the shared
  * event form for this occurrence — for recurring events the form asks how
- * far the change reaches when saving.
+ * far the change reaches when saving. [onDuplicate] opens the same form
+ * seeded with a copy of this event as a new, unsaved event (#52) — offered
+ * for any event, including read-only ones, since the copy lands in an
+ * editable calendar.
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -126,6 +131,7 @@ fun EventDetailScreen(
     endMillis: Long,
     onBack: () -> Unit,
     onEdit: () -> Unit,
+    onDuplicate: (EventForm) -> Unit,
     viewModel: EventDetailViewModel = hiltViewModel(),
 ) {
     LaunchedEffect(eventId, beginMillis, endMillis) {
@@ -160,15 +166,14 @@ fun EventDetailScreen(
     }
 
     // v1.0 installs only hold READ_CALENDAR; the first write asks for the
-    // upgrade in place. Granting continues straight into the tapped action.
-    var pendingEdit by remember { mutableStateOf(false) }
+    // upgrade in place. Granting continues straight into the tapped action —
+    // edit, delete, or duplicate — held here until the result comes back.
+    var pendingWrite by remember { mutableStateOf<(() -> Unit)?>(null) }
     val writePermissionLauncher = rememberLauncherForActivityResult(
         contract = ActivityResultContracts.RequestPermission(),
     ) { granted ->
-        if (granted) {
-            if (pendingEdit) onEdit() else showDeleteDialog = true
-        }
-        pendingEdit = false
+        if (granted) pendingWrite?.invoke()
+        pendingWrite = null
     }
     val hasWritePermission = {
         ContextCompat.checkSelfPermission(
@@ -176,21 +181,20 @@ fun EventDetailScreen(
             Manifest.permission.WRITE_CALENDAR,
         ) == PackageManager.PERMISSION_GRANTED
     }
-    val onDeleteClick = {
+    val requireWrite: (() -> Unit) -> Unit = { action ->
         if (hasWritePermission()) {
-            showDeleteDialog = true
+            action()
         } else {
-            pendingEdit = false
+            pendingWrite = action
             writePermissionLauncher.launch(Manifest.permission.WRITE_CALENDAR)
         }
     }
-    val onEditClick = {
-        if (hasWritePermission()) {
-            onEdit()
-        } else {
-            pendingEdit = true
-            writePermissionLauncher.launch(Manifest.permission.WRITE_CALENDAR)
-        }
+    val onDeleteClick = { requireWrite { showDeleteDialog = true } }
+    val onEditClick = { requireWrite(onEdit) }
+    // Duplicate reads the loaded detail into a create form and hands it up; the
+    // create still needs WRITE_CALENDAR even when the source is read-only.
+    val onDuplicateClick = {
+        requireWrite { viewModel.duplicateForm()?.let(onDuplicate) }
     }
 
     val deleteFailedMessage = stringResource(R.string.event_delete_failed)
@@ -229,7 +233,8 @@ fun EventDetailScreen(
                 },
                 actions = {
                     val s = state
-                    // Share works for any loaded event — it only reads the event.
+                    // Share and duplicate work for any loaded event — both only
+                    // read it; the duplicate is created into a writable calendar.
                     if (s is EventDetailUiState.Success) {
                         IconButton(onClick = onShareClick) {
                             Icon(
@@ -237,6 +242,15 @@ fun EventDetailScreen(
                                 contentDescription = stringResource(R.string.event_detail_share),
                             )
                         }
+                        IconButton(
+                            onClick = onDuplicateClick,
+                            enabled = deleteState != DeleteUiState.Deleting,
+                        ) {
+                            Icon(
+                                imageVector = Icons.Default.ContentCopy,
+                                contentDescription = stringResource(R.string.event_detail_duplicate),
+                            )
+                        }
                     }
                     // Edit/delete need a writable calendar — WebCal subscriptions,
                     // birthday calendars etc. are read-only at the provider level.

app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailViewModel.kt

@@ -8,10 +8,12 @@ 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.ics.IcsExporter
+import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.FailureReason
 import de.jeanlucmakiola.calendula.domain.RecurringWriteScope
 import de.jeanlucmakiola.calendula.domain.ics.IcsWriter
 import de.jeanlucmakiola.calendula.domain.ics.toShareIcsEvent
+import de.jeanlucmakiola.calendula.domain.toEditForm
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.withContext
 import kotlin.time.Clock
@@ -28,6 +30,7 @@ import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.flowOn
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
+import kotlinx.datetime.TimeZone
 import kotlin.coroutines.cancellation.CancellationException
 import kotlin.time.Instant
 import javax.inject.Inject
@@ -138,6 +141,31 @@ class EventDetailViewModel @Inject constructor(
         }.getOrNull()
     }
 
+    /**
+     * Build a create form seeded from the open event so the user can save a
+     * copy as a new, independent event (#52). Returns null when nothing is
+     * loaded.
+     *
+     * The recurrence is dropped — a duplicate is a single event; anyone who
+     * wants a series can re-add one in the edit form that opens. The source
+     * calendar is kept only when it's writable, otherwise the id is cleared so
+     * the create resolves to the last-used/first-writable calendar — which lets
+     * a read-only event (a WebCal subscription, a birthday) be copied into an
+     * editable calendar. The occurrence's own times carry over unchanged.
+     */
+    fun duplicateForm(): EventForm? {
+        val loaded = state.value as? EventDetailUiState.Success ?: return null
+        val detail = loaded.detail
+        return detail.toEditForm(
+            beginMillis = detail.instance.start.toEpochMilliseconds(),
+            endMillis = detail.instance.end.toEpochMilliseconds(),
+            zone = TimeZone.currentSystemDefault(),
+        ).copy(
+            rrule = null,
+            calendarId = detail.instance.calendarId.takeIf { loaded.canModify },
+        )
+    }
+
     private suspend fun loadDetail(target: Target): EventDetailUiState = try {
         val detail = repository.eventDetail(target.eventId)
         // The Events row holds the series start; replace it with this

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

@@ -49,6 +49,7 @@
     <string name="event_detail_edit">Edit</string>
     <string name="event_detail_delete">Delete</string>
     <string name="event_detail_share">Share</string>
+    <string name="event_detail_duplicate">Duplicate</string>
     <string name="event_share_chooser_title">Share event</string>
     <string name="event_share_failed">Couldn\'t share this event.</string>
     <string name="event_delete_title">Delete event?</string>