fix: open existing events from external VIEW intents (#48)

Follow-up to #30. v2.14.0 handles ACTION_INSERT (the widget "+"), but
tapping an existing event in a third-party widget (e.g. Todo Agenda) never
offered Calendula, because nothing handled ACTION_VIEW on
content://com.android.calendar/events/<id>.

- Manifest: add a VIEW intent-filter matched by the provider's item MIME
  type (vnd.android.cursor.item/event), mirroring AOSP Calendar and the
  sibling INSERT dir/event filter. A content: VIEW intent carries the
  resolved type, so a path-only filter wouldn't match it.
- MainActivity.viewEventKeyOrNull: parse the events URI into the existing
  occurrence detail-key channel (the one reminder taps use). Occurrence
  times ride as EXTRA_EVENT_BEGIN_TIME/END_TIME when the launcher supplies
  them; a bare URI omits them.
- EventDetailViewModel: a NO_OCCURRENCE_TIME sentinel makes loadDetail keep
  the event row's own DTSTART/DTEND for a bare URI instead of overriding to
  the epoch (would otherwise render at 1970).

Needs on-device verification (intent-filter matching + the widget's actual
extras).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -123,6 +123,22 @@
                 <data android:mimeType="vnd.android.cursor.dir/event" />
             </intent-filter>
 
+            <!-- Open an existing event another app/widget points at (e.g. tapping
+                 an event in the Todo Agenda widget): ACTION_VIEW on
+                 content://com.android.calendar/events/<id>, the way AOSP fires it.
+                 Matched by the provider's item MIME type, not the path — a
+                 content: VIEW intent carries the resolved type
+                 (vnd.android.cursor.item/event) and a path-only filter wouldn't
+                 match it. The occurrence's times ride as EXTRA_EVENT_BEGIN_TIME /
+                 EXTRA_EVENT_END_TIME when the launcher supplies them
+                 (MainActivity.viewEventKeyOrNull, issue #48). -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:mimeType="vnd.android.cursor.item/event" />
+            </intent-filter>
+
             <!-- Launcher long-press shortcuts (e.g. "New event"). -->
             <meta-data
                 android:name="android.app.shortcuts"

app/src/main/java/de/jeanlucmakiola/calendula/MainActivity.kt

@@ -32,6 +32,7 @@ import de.jeanlucmakiola.calendula.ui.common.LocalShowHourLines
 import de.jeanlucmakiola.calendula.ui.common.LocalUse24HourFormat
 import de.jeanlucmakiola.calendula.ui.WidgetNavRequest
 import de.jeanlucmakiola.calendula.ui.common.CalendarView
+import de.jeanlucmakiola.calendula.ui.detail.EventDetailViewModel.Companion.NO_OCCURRENCE_TIME
 import de.jeanlucmakiola.floret.components.DebugRibbon
 import de.jeanlucmakiola.calendula.ui.crash.CrashReportActivity
 import de.jeanlucmakiola.calendula.domain.FontRole
@@ -90,7 +91,7 @@ class MainActivity : AppCompatActivity() {
         }
 
         enableEdgeToEdge()
-        requestedDetailKey = intent.detailKeyOrNull()
+        requestedDetailKey = intent.detailKeyOrNull() ?: intent.viewEventKeyOrNull()
         requestedNav = intent.navRequestOrNull()
         requestedImportUri = intent.importUriOrNull()
         requestedInsertForm = intent.insertFormOrNull()
@@ -178,7 +179,7 @@ class MainActivity : AppCompatActivity() {
 
     override fun onNewIntent(intent: Intent) {
         super.onNewIntent(intent)
-        intent.detailKeyOrNull()?.let { requestedDetailKey = it }
+        (intent.detailKeyOrNull() ?: intent.viewEventKeyOrNull())?.let { requestedDetailKey = it }
         intent.navRequestOrNull()?.let { requestedNav = it }
         intent.importUriOrNull()?.let { requestedImportUri = it }
         intent.insertFormOrNull()?.let { requestedInsertForm = it }
@@ -293,6 +294,30 @@ class MainActivity : AppCompatActivity() {
         )
     }
 
+    /**
+     * The detail key for an external "open this event" — ACTION_VIEW on
+     * `content://com.android.calendar/events/<id>`, the way AOSP fires it (e.g.
+     * tapping an existing event in the Todo Agenda widget, issue #48). Reuses the
+     * same occurrence-key channel as reminder taps. The launcher passes the
+     * occurrence's times as `EXTRA_EVENT_BEGIN_TIME` / `EXTRA_EVENT_END_TIME` when
+     * it has them; a bare URI omits them, so we carry [NO_OCCURRENCE_TIME] and
+     * [EventDetailViewModel] falls back to the event row's own DTSTART/DTEND
+     * rather than rendering at the epoch.
+     */
+    private fun Intent.viewEventKeyOrNull(): LongArray? {
+        if (action != Intent.ACTION_VIEW) return null
+        val uri = data ?: return null
+        if (uri.host != CALENDAR_PROVIDER_HOST) return null
+        val segments = uri.pathSegments
+        if (segments.firstOrNull() != "events") return null
+        val eventId = segments.getOrNull(1)?.toLongOrNull() ?: return null
+        return longArrayOf(
+            eventId,
+            longExtraOrNull(CalendarContract.EXTRA_EVENT_BEGIN_TIME) ?: NO_OCCURRENCE_TIME,
+            longExtraOrNull(CalendarContract.EXTRA_EVENT_END_TIME) ?: NO_OCCURRENCE_TIME,
+        )
+    }
+
     companion object {
         // The calendar provider's authority/host. A date tap arrives as
         // ACTION_VIEW on content://com.android.calendar/time/<epochMillis>.

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

@@ -141,13 +141,20 @@ class EventDetailViewModel @Inject constructor(
     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
-        // occurrence's time so recurring events render correctly.
-        val corrected = detail.copy(
+        // occurrence's time so recurring events render correctly. An external
+        // "open event" that names no occurrence ([NO_OCCURRENCE_TIME] — e.g. a
+        // bare content://.../events/<id> VIEW intent, issue #48) keeps the row's
+        // own DTSTART/DTEND instead of overriding it to the epoch.
+        val corrected = if (target.beginMillis == NO_OCCURRENCE_TIME) {
+            detail
+        } else {
+            detail.copy(
                 instance = detail.instance.copy(
                     start = Instant.fromEpochMilliseconds(target.beginMillis),
                     end = Instant.fromEpochMilliseconds(target.endMillis),
                 ),
             )
+        }
         val calendar = repository.calendars().first()
             .firstOrNull { it.id == corrected.instance.calendarId }
         EventDetailUiState.Success(
@@ -168,6 +175,16 @@ class EventDetailViewModel @Inject constructor(
 
     /** A tapped occurrence: the series [eventId] plus this occurrence's own times. */
     private data class Target(val eventId: Long, val beginMillis: Long, val endMillis: Long)
+
+    companion object {
+        /**
+         * Sentinel begin/end for an "open this event" that names no occurrence —
+         * a bare `content://com.android.calendar/events/<id>` VIEW intent with no
+         * `EXTRA_EVENT_BEGIN_TIME` (issue #48). [loadDetail] then keeps the event
+         * row's own DTSTART/DTEND instead of overriding it to the epoch.
+         */
+        const val NO_OCCURRENCE_TIME: Long = Long.MIN_VALUE
+    }
 }
 
 /** A filesystem-safe `.ics` file name from an event title (or a fallback). */