feat(ics): import core — parser, dedup-aware bulk import, form prefill

v2.7 Branch 2 (core, no UI yet). The read side of the .ics engine: - domain/ics: IcsParser (inverse of IcsWriter) — unfold/unescape/param parsing, VALUE=DATE / UTC-Z / TZID date handling resolved against the OS tz db, VEVENT walk → ParsedIcsEvent + typed warnings. Liberal-in/ strict-out: a malformed VEVENT is skipped, RECURRENCE-ID overrides / attendees / unresolved TZIDs are reported, not silently dropped. - Promoted parseRfc2445DurationMillis into domain/ics (shared by writer- side mapper and parser); IcsDuration + test. - Datasource existingUids()/insertImportedEvent(); repository importEvents() with UID dedup (skip known UIDs → idempotent restore) → IcsImportSummary. IcsImporter reads a Uri's text. - ParsedIcsEvent.toEventForm() for the single-event "open into the create form" path. Parser round-trips against IcsWriter; dedup + form-adapter unit-tested. Intent filter, routing and import UI land in the next commit. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-18 14:59:32 +02:00
parent 90b219bdad
commit e1c2e9f2e5
17 changed files with 1000 additions and 55 deletions
--- a/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarDataSource.kt
@@ -18,8 +18,10 @@ import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.EventStatus
 import de.jeanlucmakiola.calendula.domain.Reminder
 import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import de.jeanlucmakiola.calendula.domain.rruleTruncatedAt
 import kotlinx.datetime.toJavaLocalDate
 import java.time.ZoneId
@@ -57,6 +59,19 @@ interface CalendarDataSource {
     */
    fun exportableEvents(): List<IcsEvent>

+    /**
+     * The non-empty `Events.UID_2445` values present in [calendarId] — used to
+     * dedup an `.ics` import so re-importing a backup doesn't double events.
+     */
+    fun existingUids(calendarId: Long): Set<String>
+
+    /**
+     * Insert a parsed `.ics` event into [calendarId], preserving its UID (or
+     * minting one when absent); returns the new `Events._ID`. Reminders are
+     * written as the file's raw lead minutes (METHOD_ALERT).
+     */
+    fun insertImportedEvent(event: ParsedIcsEvent, calendarId: Long): Long
+
    /**
     * Create a new device-only (`ACCOUNT_TYPE_LOCAL`) calendar the app owns;
     * returns its `Calendars._ID`. Inserted through the sync-adapter URI so the
@@ -307,6 +322,79 @@ class AndroidCalendarDataSource @Inject constructor(
        } ?: emptyList()
    }

+    override fun existingUids(calendarId: Long): Set<String> = resolver.query(
+        CalendarContract.Events.CONTENT_URI,
+        arrayOf(CalendarContract.Events.UID_2445),
+        "${CalendarContract.Events.CALENDAR_ID} = ? AND " +
+            "${CalendarContract.Events.UID_2445} IS NOT NULL",
+        arrayOf(calendarId.toString()),
+        null,
+    )?.use { c ->
+        buildSet { while (c.moveToNext()) c.getString(0)?.takeIf { it.isNotEmpty() }?.let(::add) }
+    } ?: emptySet()
+
+    override fun insertImportedEvent(event: ParsedIcsEvent, calendarId: Long): Long {
+        val startMillis = event.start.toEpochMillis()
+        val endMillis = event.end.toEpochMillis()
+        val values = ContentValues().apply {
+            put(CalendarContract.Events.CALENDAR_ID, calendarId)
+            // Preserve the file's UID so a re-import dedups against it; mint one
+            // only when the source event carried none.
+            put(
+                CalendarContract.Events.UID_2445,
+                event.uid?.takeIf { it.isNotBlank() } ?: "${UUID.randomUUID()}@calendula",
+            )
+            put(CalendarContract.Events.TITLE, event.summary.trim())
+            put(CalendarContract.Events.ALL_DAY, if (event.isAllDay) 1 else 0)
+            put(CalendarContract.Events.DTSTART, startMillis)
+            if (event.recurrenceRule == null) {
+                put(CalendarContract.Events.DTEND, endMillis)
+            } else {
+                put(CalendarContract.Events.RRULE, event.recurrenceRule)
+                put(
+                    CalendarContract.Events.DURATION,
+                    importDuration(startMillis, endMillis, event.isAllDay),
+                )
+            }
+            // All-day rows live at UTC midnights (the file already encodes them so);
+            // timed rows keep the event's own zone.
+            put(CalendarContract.Events.EVENT_TIMEZONE, if (event.isAllDay) "UTC" else event.zoneId)
+            put(CalendarContract.Events.AVAILABILITY, event.availability.toProviderValue())
+            put(CalendarContract.Events.STATUS, event.status.toProviderStatus())
+            event.location?.trim()?.takeIf { it.isNotEmpty() }
+                ?.let { put(CalendarContract.Events.EVENT_LOCATION, it) }
+            event.description?.trim()?.takeIf { it.isNotEmpty() }
+                ?.let { put(CalendarContract.Events.DESCRIPTION, it) }
+        }
+        val uri = resolver.insert(CalendarContract.Events.CONTENT_URI, values)
+            ?: throw WriteFailedException("import event into calendar id=$calendarId")
+        val eventId = ContentUris.parseId(uri)
+        // Raw lead minutes straight from the file's VALARMs (best-effort, like insertEvent).
+        event.reminderMinutes.distinct().filter { it >= 0 }.forEach { minutes ->
+            val reminder = ContentValues().apply {
+                put(CalendarContract.Reminders.EVENT_ID, eventId)
+                put(CalendarContract.Reminders.MINUTES, minutes)
+                put(CalendarContract.Reminders.METHOD, CalendarContract.Reminders.METHOD_ALERT)
+            }
+            if (resolver.insert(CalendarContract.Reminders.CONTENT_URI, reminder) == null) {
+                Log.w(TAG, "Failed to attach reminder ($minutes min) to imported event $eventId")
+            }
+        }
+        return eventId
+    }
+
+    /** Provider DURATION for an imported recurring row: whole days / seconds. */
+    private fun importDuration(startMillis: Long, endMillis: Long, isAllDay: Boolean): String {
+        val span = (endMillis - startMillis).coerceAtLeast(0)
+        return if (isAllDay) "P${span / 86_400_000L}D" else "P${span / 1_000L}S"
+    }
+
+    private fun EventStatus.toProviderStatus(): Int = when (this) {
+        EventStatus.Confirmed -> CalendarContract.Events.STATUS_CONFIRMED
+        EventStatus.Tentative -> CalendarContract.Events.STATUS_TENTATIVE
+        EventStatus.Cancelled -> CalendarContract.Events.STATUS_CANCELED
+    }
+
    /** The account a calendar belongs to, for scoping a `Colors` lookup. */
    private fun calendarAccount(calendarId: Long): CalendarAccount? = resolver.query(
        ContentUris.withAppendedId(CalendarContract.Calendars.CONTENT_URI, calendarId),
--- a/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepository.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepository.kt
@@ -6,6 +6,8 @@ import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
 import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
+import de.jeanlucmakiola.calendula.domain.ics.IcsImportSummary
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import kotlinx.coroutines.flow.Flow
 import kotlin.time.Instant

@@ -35,6 +37,13 @@ interface CalendarRepository {
     */
    suspend fun exportEvents(): List<IcsEvent>

+    /**
+     * Bulk-import parsed `.ics` [events] into [targetCalendarId]. Events whose
+     * UID already exists in the target are skipped (idempotent restore); the
+     * rest are inserted. See [CalendarDataSource.insertImportedEvent].
+     */
+    suspend fun importEvents(targetCalendarId: Long, events: List<ParsedIcsEvent>): IcsImportSummary
+
    /** Create a new event from a validated form; returns the new `Events._ID`. */
    suspend fun createEvent(form: EventForm): Long

--- a/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/CalendarRepositoryImpl.kt
@@ -8,6 +8,8 @@ import de.jeanlucmakiola.calendula.domain.EventColorOption
 import de.jeanlucmakiola.calendula.domain.EventDetail
 import de.jeanlucmakiola.calendula.domain.EventForm
 import de.jeanlucmakiola.calendula.domain.EventInstance
+import de.jeanlucmakiola.calendula.domain.ics.IcsImportSummary
+import de.jeanlucmakiola.calendula.domain.ics.ParsedIcsEvent
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
@@ -101,6 +103,26 @@ class CalendarRepositoryImpl @Inject constructor(

    override suspend fun exportEvents() = withContext(io) { dataSource.exportableEvents() }

+    override suspend fun importEvents(
+        targetCalendarId: Long,
+        events: List<ParsedIcsEvent>,
+    ): IcsImportSummary = withContext(io) {
+        val existing = dataSource.existingUids(targetCalendarId)
+        var imported = 0
+        var skipped = 0
+        for (event in events) {
+            // A known UID means the event is already in this calendar — skip,
+            // keeping a restore idempotent (no overwrite this pass).
+            if (event.uid != null && event.uid in existing) {
+                skipped++
+            } else {
+                dataSource.insertImportedEvent(event, targetCalendarId)
+                imported++
+            }
+        }
+        IcsImportSummary(imported = imported, skippedDuplicate = skipped)
+    }
+
    override suspend fun createEvent(form: EventForm): Long = withContext(io) {
        dataSource.insertEvent(form, allDayReminderTimeMinutes())
    }
--- a/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapper.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/data/calendar/IcsExportMapper.kt
@@ -3,6 +3,7 @@ package de.jeanlucmakiola.calendula.data.calendar
 import de.jeanlucmakiola.calendula.domain.EventStatus
 import de.jeanlucmakiola.calendula.domain.ics.IcsEvent
 import de.jeanlucmakiola.calendula.domain.ics.deriveIcsUid
+import de.jeanlucmakiola.calendula.domain.ics.parseRfc2445DurationMillis

 /**
 * Map one Events row (read through [EventExportProjection]) into an [IcsEvent]
@@ -51,41 +52,3 @@ internal fun ColumnReader.toIcsEvent(
    )
 }

-// Android's calendar provider (and Calendula's own writes) use the non-standard
-// single-unit forms P<n>S / P<n>D / P<n>W — seconds without the RFC-required
-// leading T. Matched first; anything else falls through to the general grammar.
-private val DURATION_SINGLE_UNIT = Regex("""([+-]?)P(\d+)([WDS])""")
-private val DURATION_GENERAL =
-    Regex("""([+-]?)P(?:(\d+)W)?(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?""")
-
-/**
- * Milliseconds of a DURATION (`P1D`, `P3600S`, `PT1H30M`, `P1W`, …). Calendula
- * only ever writes `P<days>D` / `P<seconds>S`, but the parser also handles the
- * general RFC 5545 grammar so a foreign row on a local calendar still
- * round-trips. Unparseable input is treated as zero.
- */
-internal fun parseRfc2445DurationMillis(duration: String?): Long {
-    if (duration.isNullOrBlank()) return 0L
-    val s = duration.trim()
-
-    DURATION_SINGLE_UNIT.matchEntire(s)?.let { m ->
-        val unitSeconds = when (m.groupValues[3]) {
-            "W" -> 7L * 24 * 60 * 60
-            "D" -> 24L * 60 * 60
-            else -> 1L // S
-        }
-        return m.signum() * m.groupValues[2].toLong() * unitSeconds * 1_000L
-    }
-
-    val m = DURATION_GENERAL.matchEntire(s) ?: return 0L
-    val weeks = m.groupValues[2].toLongOrNull() ?: 0L
-    val days = m.groupValues[3].toLongOrNull() ?: 0L
-    val hours = m.groupValues[4].toLongOrNull() ?: 0L
-    val minutes = m.groupValues[5].toLongOrNull() ?: 0L
-    val seconds = m.groupValues[6].toLongOrNull() ?: 0L
-    val totalSeconds = ((((weeks * 7 + days) * 24 + hours) * 60 + minutes) * 60 + seconds)
-    return m.signum() * totalSeconds * 1_000L
-}
-
-/** Sign carried by group 1 (`-` → -1, otherwise +1) of a duration match. */
-private fun MatchResult.signum(): Long = if (groupValues[1] == "-") -1L else 1L
--- a/app/src/main/java/de/jeanlucmakiola/calendula/data/ics/IcsImporter.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/data/ics/IcsImporter.kt
@@ -0,0 +1,21 @@
+package de.jeanlucmakiola.calendula.data.ics
+
+import android.content.Context
+import android.net.Uri
+import dagger.hilt.android.qualifiers.ApplicationContext
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Android IO edge of `.ics` import: reads the text of a received/opened
+ * document [Uri]. Parsing is the pure `domain.ics.IcsParser`; this class only
+ * pulls bytes off the ContentResolver. Returns null on any read failure.
+ */
+@Singleton
+class IcsImporter @Inject constructor(
+    @ApplicationContext private val context: Context,
+) {
+    fun readText(uri: Uri): String? = runCatching {
+        context.contentResolver.openInputStream(uri)?.use { it.readBytes().toString(Charsets.UTF_8) }
+    }.getOrNull()
+}
--- a/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsDuration.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsDuration.kt
@@ -0,0 +1,40 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+// Android's calendar provider (and Calendula's own writes) use the non-standard
+// single-unit forms P<n>S / P<n>D / P<n>W — seconds without the RFC-required
+// leading T. Matched first; anything else falls through to the general grammar.
+private val DURATION_SINGLE_UNIT = Regex("""([+-]?)P(\d+)([WDS])""")
+private val DURATION_GENERAL =
+    Regex("""([+-]?)P(?:(\d+)W)?(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?""")
+
+/**
+ * Milliseconds of a DURATION (`P1D`, `P3600S`, `PT1H30M`, `-PT15M`, `P1W`, …),
+ * sign-aware. Calendula writes `P<days>D` / `P<seconds>S`, but the parser also
+ * accepts the general RFC 5545 grammar so backup `DURATION` rows and foreign
+ * `VALARM` triggers round-trip. Unparseable input is treated as zero.
+ */
+fun parseRfc2445DurationMillis(duration: String?): Long {
+    if (duration.isNullOrBlank()) return 0L
+    val s = duration.trim()
+
+    DURATION_SINGLE_UNIT.matchEntire(s)?.let { m ->
+        val unitSeconds = when (m.groupValues[3]) {
+            "W" -> 7L * 24 * 60 * 60
+            "D" -> 24L * 60 * 60
+            else -> 1L // S
+        }
+        return m.signum() * m.groupValues[2].toLong() * unitSeconds * 1_000L
+    }
+
+    val m = DURATION_GENERAL.matchEntire(s) ?: return 0L
+    val weeks = m.groupValues[2].toLongOrNull() ?: 0L
+    val days = m.groupValues[3].toLongOrNull() ?: 0L
+    val hours = m.groupValues[4].toLongOrNull() ?: 0L
+    val minutes = m.groupValues[5].toLongOrNull() ?: 0L
+    val seconds = m.groupValues[6].toLongOrNull() ?: 0L
+    val totalSeconds = ((((weeks * 7 + days) * 24 + hours) * 60 + minutes) * 60 + seconds)
+    return m.signum() * totalSeconds * 1_000L
+}
+
+/** Sign carried by group 1 (`-` → -1, otherwise +1) of a duration match. */
+private fun MatchResult.signum(): Long = if (groupValues[1] == "-") -1L else 1L
--- a/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsParser.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsParser.kt
@@ -0,0 +1,259 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.Availability
+import de.jeanlucmakiola.calendula.domain.EventStatus
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.atStartOfDayIn
+import kotlinx.datetime.toInstant
+import kotlin.time.Instant
+
+/**
+ * A `VEVENT` parsed from an `.ics` file — the read-side mirror of [IcsEvent],
+ * but [uid] is nullable (an incoming event may carry none; the insert layer
+ * then assigns one). Times are absolute instants; [isAllDay]/[zoneId] mirror
+ * how the writer encoded them.
+ */
+data class ParsedIcsEvent(
+    val uid: String?,
+    val summary: String,
+    val start: Instant,
+    val end: Instant,
+    val isAllDay: Boolean,
+    val zoneId: String,
+    val recurrenceRule: String? = null,
+    val location: String? = null,
+    val description: String? = null,
+    val reminderMinutes: List<Int> = emptyList(),
+    val status: EventStatus = EventStatus.Confirmed,
+    val availability: Availability = Availability.Busy,
+    val calendarName: String? = null,
+)
+
+/** Things the parser dropped rather than failing — surfaced in the import report. */
+enum class IcsParseWarning {
+    /** A `RECURRENCE-ID` override occurrence (not modelled; only masters import). */
+    ModifiedOccurrenceSkipped,
+
+    /** A `VEVENT` with no parseable `DTSTART`. */
+    EventWithoutStartSkipped,
+
+    /** `ATTENDEE` rows were present; Calendula doesn't import attendees. */
+    AttendeesIgnored,
+
+    /** A `TZID` couldn't be resolved against the device tz database (used local zone). */
+    UnknownTimezone,
+}
+
+data class IcsParseResult(
+    val events: List<ParsedIcsEvent>,
+    val warnings: Set<IcsParseWarning>,
+)
+
+/** Outcome of a bulk `.ics` import into one calendar. */
+data class IcsImportSummary(val imported: Int, val skippedDuplicate: Int)
+
+/**
+ * Hand-rolled RFC 5545 reader, the inverse of [IcsWriter]. Pure and
+ * JVM-testable. Liberal-in/strict-out: unknown properties are ignored, a single
+ * malformed `VEVENT` is skipped (not fatal), and unsupported constructs
+ * (`RECURRENCE-ID`, attendees, unresolved `TZID`) are reported as [warnings]
+ * rather than silently dropped. `VTIMEZONE` blocks are skipped — a `TZID` is
+ * resolved against the OS tz database instead ([deviceZone] is the fallback).
+ */
+class IcsParser(private val deviceZone: TimeZone = TimeZone.currentSystemDefault()) {
+
+    fun parse(text: String): IcsParseResult {
+        val lines = unfoldLines(text)
+        val events = mutableListOf<ParsedIcsEvent>()
+        val warnings = mutableSetOf<IcsParseWarning>()
+        var calendarName: String? = null
+
+        var i = 0
+        while (i < lines.size) {
+            val line = parseContentLine(lines[i])
+            if (line == null) { i++; continue }
+            when {
+                line.isBegin("VEVENT") -> {
+                    val end = indexOfEnd(lines, i + 1, "VEVENT")
+                    parseVevent(lines.subList(i + 1, end), calendarName, warnings)
+                        ?.let(events::add)
+                    i = end + 1
+                }
+                line.isBegin("VTIMEZONE") -> {
+                    // Skipped wholesale; TZIDs resolve against the OS tz database.
+                    i = indexOfEnd(lines, i + 1, "VTIMEZONE") + 1
+                }
+                line.name == "X-WR-CALNAME" -> {
+                    calendarName = unescapeText(line.value).trim().ifEmpty { null }
+                    i++
+                }
+                else -> i++
+            }
+        }
+        return IcsParseResult(events, warnings)
+    }
+
+    private fun parseVevent(
+        body: List<String>,
+        fileCalendarName: String?,
+        warnings: MutableSet<IcsParseWarning>,
+    ): ParsedIcsEvent? {
+        var uid: String? = null
+        var summary = ""
+        var dtStart: IcsDateTime? = null
+        var dtEnd: IcsDateTime? = null
+        var duration: String? = null
+        var rrule: String? = null
+        var location: String? = null
+        var description: String? = null
+        var status = EventStatus.Confirmed
+        var availability = Availability.Busy
+        var calendarName = fileCalendarName
+        val reminders = mutableListOf<Int>()
+        var skipAsOverride = false
+
+        var i = 0
+        while (i < body.size) {
+            val line = parseContentLine(body[i])
+            if (line == null) { i++; continue }
+            when (line.name) {
+                "BEGIN" -> if (line.value.trim().equals("VALARM", true)) {
+                    val end = indexOfEnd(body, i + 1, "VALARM")
+                    parseAlarmMinutes(body.subList(i + 1, end))?.let(reminders::add)
+                    i = end + 1
+                    continue
+                }
+                "UID" -> uid = line.value.trim().ifEmpty { null }
+                "SUMMARY" -> summary = unescapeText(line.value)
+                "DTSTART" -> dtStart = parseIcsDateTime(line, warnings)
+                "DTEND" -> dtEnd = parseIcsDateTime(line, warnings)
+                "DURATION" -> duration = line.value.trim()
+                "RRULE" -> rrule = line.value.trim().ifEmpty { null }
+                "LOCATION" -> location = unescapeText(line.value).ifEmpty { null }
+                "DESCRIPTION" -> description = unescapeText(line.value).ifEmpty { null }
+                "STATUS" -> status = mapIcsStatus(line.value)
+                "TRANSP" -> availability =
+                    if (line.value.trim().equals("TRANSPARENT", true)) Availability.Free
+                    else Availability.Busy
+                "RECURRENCE-ID" -> skipAsOverride = true
+                "ATTENDEE" -> warnings.add(IcsParseWarning.AttendeesIgnored)
+                "X-CALENDULA-CALENDAR" ->
+                    calendarName = unescapeText(line.value).trim().ifEmpty { calendarName }
+            }
+            i++
+        }
+
+        if (skipAsOverride) {
+            warnings.add(IcsParseWarning.ModifiedOccurrenceSkipped)
+            return null
+        }
+        val start = dtStart ?: run {
+            warnings.add(IcsParseWarning.EventWithoutStartSkipped)
+            return null
+        }
+        val end = dtEnd
+            ?: duration?.let {
+                start.copy(
+                    instant = Instant.fromEpochMilliseconds(
+                        start.instant.toEpochMilliseconds() + parseRfc2445DurationMillis(it),
+                    ),
+                )
+            }
+            ?: start
+        return ParsedIcsEvent(
+            uid = uid,
+            summary = summary,
+            start = start.instant,
+            end = end.instant,
+            isAllDay = start.isAllDay,
+            zoneId = start.zoneId,
+            recurrenceRule = rrule,
+            location = location,
+            description = description,
+            reminderMinutes = reminders.distinct(),
+            status = status,
+            availability = availability,
+            calendarName = calendarName,
+        )
+    }
+
+    /** A VALARM's lead time in minutes before start, or null if not a usable relative trigger. */
+    private fun parseAlarmMinutes(body: List<String>): Int? {
+        val trigger = body.asSequence()
+            .mapNotNull { parseContentLine(it) }
+            .firstOrNull { it.name == "TRIGGER" }
+            ?: return null
+        // Absolute (DATE-TIME) triggers can't be expressed as a lead time.
+        if (trigger.params["VALUE"].equals("DATE-TIME", true)) return null
+        val millis = parseRfc2445DurationMillis(trigger.value)
+        // Negative = before start (the normal case) → positive lead minutes.
+        return (-millis / 60_000L).toInt().coerceAtLeast(0)
+    }
+
+    private fun parseIcsDateTime(line: IcsContentLine, warnings: MutableSet<IcsParseWarning>): IcsDateTime? {
+        val raw = line.value.trim()
+        val isDate = line.params["VALUE"].equals("DATE", true) ||
+            (raw.length == 8 && !raw.contains('T'))
+        if (isDate) {
+            val date = parseBasicDate(raw) ?: return null
+            return IcsDateTime(date.atStartOfDayIn(TimeZone.UTC), isAllDay = true, zoneId = "UTC")
+        }
+        val isUtc = raw.endsWith("Z")
+        val ldt = parseBasicDateTime(raw.removeSuffix("Z")) ?: return null
+        if (isUtc) return IcsDateTime(ldt.toInstant(TimeZone.UTC), isAllDay = false, zoneId = "UTC")
+
+        val tzid = line.params["TZID"]
+        val resolved = tzid?.let { id -> runCatching { TimeZone.of(id) }.getOrNull()?.let { id to it } }
+        if (tzid != null && resolved == null) warnings.add(IcsParseWarning.UnknownTimezone)
+        val (zoneId, zone) = resolved ?: (deviceZone.id to deviceZone)
+        return IcsDateTime(ldt.toInstant(zone), isAllDay = false, zoneId = zoneId)
+    }
+
+    private data class IcsDateTime(val instant: Instant, val isAllDay: Boolean, val zoneId: String)
+
+    private companion object {
+        fun IcsContentLine.isBegin(component: String) =
+            name == "BEGIN" && value.trim().equals(component, true)
+
+        /** Index of the matching `END:<component>` at/after [from], or list end. */
+        fun indexOfEnd(lines: List<String>, from: Int, component: String): Int {
+            var i = from
+            while (i < lines.size) {
+                val line = parseContentLine(lines[i])
+                if (line != null && line.name == "END" &&
+                    line.value.trim().equals(component, true)
+                ) {
+                    return i
+                }
+                i++
+            }
+            return lines.size
+        }
+
+        fun mapIcsStatus(value: String): EventStatus = when (value.trim().uppercase()) {
+            "TENTATIVE" -> EventStatus.Tentative
+            "CANCELLED" -> EventStatus.Cancelled
+            else -> EventStatus.Confirmed
+        }
+
+        fun parseBasicDate(s: String): LocalDate? = runCatching {
+            LocalDate(s.substring(0, 4).toInt(), s.substring(4, 6).toInt(), s.substring(6, 8).toInt())
+        }.getOrNull()
+
+        fun parseBasicDateTime(s: String): LocalDateTime? = runCatching {
+            val date = LocalDate(
+                s.substring(0, 4).toInt(), s.substring(4, 6).toInt(), s.substring(6, 8).toInt(),
+            )
+            // Format is YYYYMMDD 'T' HHMMSS; seconds optional.
+            val time = LocalTime(
+                s.substring(9, 11).toInt(),
+                s.substring(11, 13).toInt(),
+                if (s.length >= 15) s.substring(13, 15).toInt() else 0,
+            )
+            LocalDateTime(date, time)
+        }.getOrNull()
+    }
+}
--- a/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsText.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/IcsText.kt
@@ -60,3 +60,96 @@ fun foldLine(line: String): String {
    }
    return out.toString()
 }
+
+/**
+ * Reverse of [escapeText]: turn `\n`/`\N` into newlines and unescape `\\`, `\;`,
+ * `\,`. A backslash before any other character is dropped, keeping the
+ * character (lenient — foreign files escape liberally).
+ */
+fun unescapeText(value: String): String = buildString(value.length) {
+    var i = 0
+    while (i < value.length) {
+        val c = value[i]
+        if (c == '\\' && i + 1 < value.length) {
+            when (val next = value[i + 1]) {
+                'n', 'N' -> append('\n')
+                else -> append(next) // \\, \;, \, and any other escaped char
+            }
+            i += 2
+        } else {
+            append(c)
+            i++
+        }
+    }
+}
+
+/**
+ * Reverse of [foldLine] across a whole document: split into physical lines on
+ * CRLF/LF/CR, then re-join any line that begins with a single space or tab onto
+ * the previous one (RFC 5545 unfolding). Returns the logical content lines.
+ */
+fun unfoldLines(text: String): List<String> {
+    val out = mutableListOf<String>()
+    for (physical in text.split("\r\n", "\n", "\r")) {
+        if (physical.isEmpty()) continue
+        val isContinuation = physical[0] == ' ' || physical[0] == '\t'
+        if (isContinuation && out.isNotEmpty()) {
+            out[out.lastIndex] = out.last() + physical.substring(1)
+        } else {
+            out.add(physical)
+        }
+    }
+    return out
+}
+
+/**
+ * One unfolded content line split into its property name, parameters and value:
+ * `SUMMARY;LANGUAGE=en:Lunch` → name `SUMMARY`, params `{LANGUAGE=en}`, value
+ * `Lunch`. The value is everything after the first colon that isn't inside a
+ * quoted parameter; param keys are upper-cased, quoted param values unquoted.
+ * Returns null for a line with no colon.
+ */
+data class IcsContentLine(val name: String, val params: Map<String, String>, val value: String)
+
+fun parseContentLine(line: String): IcsContentLine? {
+    var inQuote = false
+    var colon = -1
+    for (i in line.indices) {
+        when (line[i]) {
+            '"' -> inQuote = !inQuote
+            ':' -> if (!inQuote) { colon = i; break }
+        }
+    }
+    if (colon < 0) return null
+    val head = splitUnquoted(line.substring(0, colon), ';')
+    val name = head.firstOrNull()?.trim()?.uppercase().orEmpty()
+    if (name.isEmpty()) return null
+    val params = buildMap {
+        for (part in head.drop(1)) {
+            val eq = part.indexOf('=')
+            if (eq > 0) {
+                put(
+                    part.substring(0, eq).trim().uppercase(),
+                    part.substring(eq + 1).trim().removeSurrounding("\""),
+                )
+            }
+        }
+    }
+    return IcsContentLine(name, params, line.substring(colon + 1))
+}
+
+/** Split on [delimiter] except where it falls inside a double-quoted run. */
+private fun splitUnquoted(text: String, delimiter: Char): List<String> {
+    val parts = mutableListOf<String>()
+    val current = StringBuilder()
+    var inQuote = false
+    for (c in text) {
+        when {
+            c == '"' -> { inQuote = !inQuote; current.append(c) }
+            c == delimiter && !inQuote -> { parts.add(current.toString()); current.clear() }
+            else -> current.append(c)
+        }
+    }
+    parts.add(current.toString())
+    return parts
+}
--- a/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/ParsedIcsForm.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/domain/ics/ParsedIcsForm.kt
@@ -0,0 +1,38 @@
+package de.jeanlucmakiola.calendula.domain.ics
+
+import de.jeanlucmakiola.calendula.domain.EventForm
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.LocalTime
+import kotlinx.datetime.TimeZone
+import kotlinx.datetime.toLocalDateTime
+
+/**
+ * Prefill the create form from a single parsed `.ics` event (the "open one
+ * event" path). [calendarId] is left null so the form preselects the last-used
+ * calendar, exactly like a fresh create — the user confirms the target and
+ * reviews everything before saving. Mirrors `EventDetail.toEditForm`'s all-day
+ * handling (provider all-day times are UTC midnights with an exclusive end).
+ */
+fun ParsedIcsEvent.toEventForm(zone: TimeZone): EventForm {
+    val (start, end) = if (isAllDay) {
+        val startDate = this.start.toLocalDateTime(TimeZone.UTC).date
+        val endExclusive = this.end.toLocalDateTime(TimeZone.UTC).date
+        val endDate = maxOf(startDate, LocalDate.fromEpochDays(endExclusive.toEpochDays() - 1))
+        LocalDateTime(startDate, LocalTime(9, 0)) to LocalDateTime(endDate, LocalTime(10, 0))
+    } else {
+        this.start.toLocalDateTime(zone) to this.end.toLocalDateTime(zone)
+    }
+    return EventForm(
+        calendarId = null,
+        title = summary,
+        isAllDay = isAllDay,
+        start = start,
+        end = end,
+        location = location.orEmpty(),
+        description = description.orEmpty(),
+        reminders = reminderMinutes.distinct().sorted(),
+        availability = availability,
+        rrule = recurrenceRule?.removePrefix("RRULE:")?.takeIf { it.isNotBlank() },
+    )
+}
--- a/app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailScreen.kt
+++ b/app/src/main/java/de/jeanlucmakiola/calendula/ui/detail/EventDetailScreen.kt
@@ -776,14 +776,19 @@ private fun formatWhen(
    val allDayLabel = stringResource(R.string.event_detail_all_day)

    if (instance.isAllDay) {
-        // All-day end is the exclusive next midnight; step back to the last
-        // covered day so a one-day event reads as a single date.
-        val lastLdt = (instance.end - 1.seconds).toJavaLocalDateTime(zid)
-        return if (startLdt.toLocalDate() == lastLdt.toLocalDate()) {
-            allDayLabel to dateFull.format(startLdt.toLocalDate())
+        // All-day events live at UTC midnights with an exclusive end. Resolve
+        // the covered dates in UTC — not the device zone, which would shift the
+        // midnight boundaries off the intended date (east of UTC pushes the
+        // end past the last day; west of UTC pulls the start back) — and step
+        // the end back to the last covered day so a one-day event reads as a
+        // single date.
+        val utc = ZoneId.of("UTC")
+        val startDate = instance.start.toJavaLocalDateTime(utc).toLocalDate()
+        val lastDate = (instance.end - 1.seconds).toJavaLocalDateTime(utc).toLocalDate()
+        return if (startDate == lastDate) {
+            allDayLabel to dateFull.format(startDate)
        } else {
-            allDayLabel to
-                "${dateMedium.format(startLdt.toLocalDate())} – ${dateMedium.format(lastLdt.toLocalDate())}"
+            allDayLabel to "${dateMedium.format(startDate)} – ${dateMedium.format(lastDate)}"
        }
    }