feat: edit or delete one occurrence of a repeating event

2 files changed, 122 insertions, 3 deletions

diff --git a/src/calendarstore.cpp b/src/calendarstore.cpp
index c388cd6..ef67eba 100644
--- a/src/calendarstore.cpp
+++ b/src/calendarstore.cpp
@@ -385,9 +385,26 @@ QByteArray serialise(icalcomponent *root)
     return text ? QByteArray(text.get()) : QByteArray();
 }
 
-icalcomponent *overrideFor(icalcomponent *, icalcomponent *master, const QDateTime &)
+/// The override component for `recurrenceId`, created when absent: a copy of
+/// the master without RRULE, RDATE or EXDATE, carrying a RECURRENCE-ID in the
+/// master's own time form.
+icalcomponent *overrideFor(icalcomponent *root, icalcomponent *master,
+                           const QDateTime &recurrenceId)
 {
-    return master;  // replaced in Task 7
+    for (icalcomponent *c = icalcomponent_get_first_component(root, ICAL_VEVENT_COMPONENT);
+         c; c = icalcomponent_get_next_component(root, ICAL_VEVENT_COMPONENT)) {
+        icalproperty *rid = icalcomponent_get_first_property(c, ICAL_RECURRENCEID_PROPERTY);
+        if (c != master && rid
+            && toDateTime(icalcomponent_get_recurrenceid(c), tzidOf(rid), nullptr) == recurrenceId)
+            return c;
+    }
+    icalcomponent *copy = icalcomponent_new_clone(master);
+    removeAll(copy, ICAL_RRULE_PROPERTY);
+    removeAll(copy, ICAL_RDATE_PROPERTY);
+    removeAll(copy, ICAL_EXDATE_PROPERTY);
+    setTime(copy, ICAL_RECURRENCEID_PROPERTY, recurrenceId, formOf(root, master));
+    icalcomponent_add_component(root, copy);
+    return copy;
 }
 
 } // namespace
@@ -595,7 +612,35 @@ QByteArray newEvent(const EventEdit &edit, const QByteArray &zoneId)
     return serialise(root.get());
 }
 
-QByteArray deleteOccurrence(const QByteArray &, const QDateTime &) { return {}; }
+QByteArray deleteOccurrence(const QByteArray &text, const QDateTime &recurrenceId)
+{
+    IcalComponent root = parseRoot(text);
+    icalcomponent *master = root ? masterOf(root.get()) : nullptr;
+    if (!master)
+        return {};
+    // Collect first: removing a component mid-walk invalidates the iterator.
+    QList<icalcomponent *> doomed;
+    for (icalcomponent *c = icalcomponent_get_first_component(root.get(), ICAL_VEVENT_COMPONENT);
+         c; c = icalcomponent_get_next_component(root.get(), ICAL_VEVENT_COMPONENT)) {
+        icalproperty *rid = icalcomponent_get_first_property(c, ICAL_RECURRENCEID_PROPERTY);
+        if (c != master && rid
+            && toDateTime(icalcomponent_get_recurrenceid(c), tzidOf(rid), nullptr) == recurrenceId)
+            doomed.append(c);
+    }
+    for (icalcomponent *c : doomed) {
+        icalcomponent_remove_component(root.get(), c);
+        icalcomponent_free(c);
+    }
+    // setTime replaces every property of its kind, which for EXDATE would
+    // drop the existing ones: add this one alongside instead.
+    const TimeForm form = formOf(root.get(), master);
+    icalproperty *ex = icalproperty_new_exdate(wallTime(recurrenceId, form));
+    if (form.kind == TimeForm::Zoned)
+        icalproperty_add_parameter(ex, icalparameter_new_tzid(form.tzid.constData()));
+    icalcomponent_add_property(master, ex);
+    stamp(master, true);
+    return serialise(root.get());
+}
 
 bool sameMeaning(const QByteArray &a, const QByteArray &b)
 {
diff --git a/tests/test_calendarstore.cpp b/tests/test_calendarstore.cpp
index ba2d5c7..921a194 100644
--- a/tests/test_calendarstore.cpp
+++ b/tests/test_calendarstore.cpp
@@ -23,6 +23,8 @@
 #include <QTemporaryDir>
 #include <QTimeZone>
 
+#include <algorithm>
+
 #include "calendarstore.h"
 
 namespace {
@@ -98,6 +100,16 @@ CalEvent reparse(const QByteArray &text)
     return CalendarStore::parseEvent(text, QStringLiteral("/x/e.ics"), QStringLiteral("x"), &unknown);
 }
 
+const QString kDailySeries = QStringLiteral(
+    "UID:d@example.org\r\nDTSTAMP:20260901T000000Z\r\n"
+    "DTSTART;TZID=Europe/Rome:20260921T100000\r\nDTEND;TZID=Europe/Rome:20260921T110000\r\n"
+    "RRULE:FREQ=DAILY;COUNT=5\r\nSUMMARY:Daily\r\n");
+
+QDateTime rome(int d, int h)
+{
+    return QDateTime(QDate(2026, 9, d), QTime(h, 0), QTimeZone("Europe/Rome"));
+}
+
 const QString kRichEvent = QStringLiteral(
     "UID:rich@example.org\r\nDTSTAMP:20260901T000000Z\r\nSEQUENCE:2\r\n"
     "DTSTART;TZID=Europe/Rome:20260922T100000\r\nDTEND;TZID=Europe/Rome:20260922T110000\r\n"
@@ -141,6 +153,10 @@ private slots:
     void sameMeaningIgnoresFormatting();
     void sameMeaningMatchesOverridesRegardlessOfOrder();
     void sameMeaningRejectsDifferentUids();
+
+    void editingOneOccurrenceWritesAnOverride();
+    void editingTheSameOccurrenceAgainReplacesItsOverride();
+    void deletingOneOccurrenceAddsAnExdateAndDropsItsOverride();
 };
 
 void TestCalendarStore::parsesAUtcEvent()
@@ -587,5 +603,63 @@ void TestCalendarStore::sameMeaningRejectsDifferentUids()
     QVERIFY(CalendarStore::sameMeaning(a, a));
 }
 
+void TestCalendarStore::editingOneOccurrenceWritesAnOverride()
+{
+    const CalEvent series = parse(vevent(kDailySeries));
+    EventEdit edit = editOf(series);
+    edit.summary = QStringLiteral("Just this one");
+    edit.start = rome(22, 15);
+    edit.end = rome(22, 16);
+    const QByteArray after = CalendarStore::applyEdit(
+        series.rawText, edit, CalendarStore::Scope::ThisOccurrence, rome(22, 10));
+
+    const CalEvent e = reparse(after);
+    QCOMPARE(e.summary, QStringLiteral("Daily"));          // master untouched
+    QCOMPARE(e.repeat.count, 5);
+    QCOMPARE(e.overrides.size(), 1);
+    QCOMPARE(e.overrides[0].recurrenceId, rome(22, 10));
+    QCOMPARE(e.overrides[0].summary, QStringLiteral("Just this one"));
+    QCOMPARE(after.count("RRULE"), 1);                     // the override carries none
+
+    const QList<Occurrence> occ = CalendarStore::occurrences(
+        { e }, rome(21, 0), rome(26, 0));
+    QCOMPARE(occ.size(), 5);                               // still five, one moved
+    QVERIFY(std::any_of(occ.cbegin(), occ.cend(),
+                        [](const Occurrence &o) { return o.isOverride && o.start == rome(22, 15); }));
+}
+
+void TestCalendarStore::editingTheSameOccurrenceAgainReplacesItsOverride()
+{
+    const CalEvent series = parse(vevent(kDailySeries));
+    EventEdit edit = editOf(series);
+    edit.start = rome(22, 15);
+    edit.end = rome(22, 16);
+    QByteArray text = CalendarStore::applyEdit(
+        series.rawText, edit, CalendarStore::Scope::ThisOccurrence, rome(22, 10));
+    edit.start = rome(22, 17);
+    edit.end = rome(22, 18);
+    text = CalendarStore::applyEdit(text, edit, CalendarStore::Scope::ThisOccurrence, rome(22, 10));
+    const CalEvent e = reparse(text);
+    QCOMPARE(e.overrides.size(), 1);
+    QCOMPARE(e.overrides[0].start, rome(22, 17));
+}
+
+void TestCalendarStore::deletingOneOccurrenceAddsAnExdateAndDropsItsOverride()
+{
+    const CalEvent series = parse(vevent(kDailySeries));
+    EventEdit edit = editOf(series);
+    edit.start = rome(23, 15);
+    edit.end = rome(23, 16);
+    const QByteArray withOverride = CalendarStore::applyEdit(
+        series.rawText, edit, CalendarStore::Scope::ThisOccurrence, rome(23, 10));
+
+    const QByteArray after = CalendarStore::deleteOccurrence(withOverride, rome(23, 10));
+    const CalEvent e = reparse(after);
+    QCOMPARE(e.overrides.size(), 0);
+    QCOMPARE(e.exdates, QList<QDateTime>{ rome(23, 10) });
+    QVERIFY2(after.contains("EXDATE;TZID=Europe/Rome:20260923T100000"), after.constData());
+    QCOMPARE(CalendarStore::occurrences({ e }, rome(21, 0), rome(26, 0)).size(), 4);
+}
+
 QTEST_MAIN(TestCalendarStore)
 #include "test_calendarstore.moc"