feat(android): back the calendars up as an iCalendar file

A Calendar section sends every calendar the person can edit, as a dated .ics,
into <folder>/<account>-calendar once a day when it changed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/IcsTest.kt b/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/IcsTest.kt
new file mode 100644
index 0000000..c8f8fa3
--- /dev/null
+++ b/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/IcsTest.kt
@@ -0,0 +1,117 @@
+package org.meshbay.client
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.meshbay.client.phonesync.Attendee
+import org.meshbay.client.phonesync.CalEvent
+import org.meshbay.client.phonesync.Ics
+
+class IcsTest {
+    // 2026-10-09 12:00:00 UTC
+    private val oct9 = 1791547200000L
+    private val hour = 3600_000L
+
+    private fun event(id: Long, title: String = "Lunch", start: Long = oct9, end: Long? = oct9 + hour,
+                      duration: String? = null, allDay: Boolean = false, zone: String? = "Europe/Paris",
+                      rrule: String? = null, exdate: String? = null, originalId: Long? = null,
+                      originalTime: Long? = null, uid: String? = null, status: Int? = 1,
+                      reminders: List<Int> = emptyList(), attendees: List<Attendee> = emptyList(),
+                      description: String? = null) =
+        CalEvent(id, "Personal", uid, title, description, null, start, end, duration, allDay, zone,
+                 rrule, null, exdate, originalId, originalTime, false, status, reminders, null, attendees)
+
+    private fun lines(vararg e: CalEvent): List<String> {
+        val out = ArrayList<String>()
+        Ics.write(e.toList(), oct9) { out += it }
+        return out
+    }
+
+    /** RFC 5545 unfolding: a line starting with a space continues the one before. */
+    private fun unfold(l: List<String>): List<String> {
+        val out = ArrayList<String>()
+        for (x in l) if (x.startsWith(" ")) out[out.size - 1] = out.last() + x.substring(1) else out += x
+        return out
+    }
+
+    private fun events(l: List<String>): List<List<String>> {
+        val out = ArrayList<List<String>>()
+        var cur: MutableList<String>? = null
+        for (x in unfold(l)) when (x) {
+            "BEGIN:VEVENT" -> cur = ArrayList()
+            "END:VEVENT" -> { out += cur!!; cur = null }
+            else -> cur?.add(x)
+        }
+        return out
+    }
+
+    private fun List<String>.prop(name: String) = firstOrNull { it.startsWith("$name:") || it.startsWith("$name;") }
+
+    @Test fun `a calendar wraps the events, with what an importer requires`() {
+        val l = lines(event(1))
+        assertEquals("BEGIN:VCALENDAR", l.first())
+        assertEquals("END:VCALENDAR", l.last())
+        assertTrue("VERSION:2.0" in l)
+        val e = events(l).single()
+        assertEquals("UID:android-1@meshbay", e.prop("UID"))
+        assertEquals("DTSTAMP:20261009T120000Z", e.prop("DTSTAMP"))
+    }
+
+    @Test fun `a timed event keeps its zone, so a recurrence follows summer time`() {
+        val e = events(lines(event(1)))[0]
+        assertEquals("DTSTART;TZID=Europe/Paris:20261009T140000", e.prop("DTSTART"))
+        assertEquals("DTEND;TZID=Europe/Paris:20261009T150000", e.prop("DTEND"))
+        val utc = events(lines(event(2, zone = null)))[0]
+        assertEquals("DTSTART:20261009T120000Z", utc.prop("DTSTART"))
+        val unknown = events(lines(event(3, zone = "Not/AZone")))[0]
+        assertEquals("DTSTART:20261009T120000Z", unknown.prop("DTSTART"))
+    }
+
+    @Test fun `an all-day event is a date`() {
+        val day = 1791504000000L // 2026-10-09 00:00 UTC
+        val e = events(lines(event(1, start = day, end = day + 24 * hour, allDay = true)))[0]
+        assertEquals("DTSTART;VALUE=DATE:20261009", e.prop("DTSTART"))
+        assertEquals("DTEND;VALUE=DATE:20261010", e.prop("DTEND"))
+    }
+
+    @Test fun `a recurring event keeps its rule, and Android's duration is made valid`() {
+        val e = events(lines(event(1, end = null, duration = "P3600S", rrule = "FREQ=WEEKLY;BYDAY=FR",
+                                   exdate = "Europe/Paris;20261016T140000")))[0]
+        assertEquals("RRULE:FREQ=WEEKLY;BYDAY=FR", e.prop("RRULE"))
+        assertEquals("DURATION:PT3600S", e.prop("DURATION"))
+        assertEquals("EXDATE;TZID=Europe/Paris:20261016T140000", e.prop("EXDATE"))
+        assertNull(e.prop("DTEND"))
+        assertEquals("P1D", Ics.duration("P1D"))
+        assertEquals("PT1H30M", Ics.duration("PT1H30M"))
+        assertNull(Ics.duration("nonsense"))
+    }
+
+    @Test fun `a changed instance carries the series' UID and says which instance`() {
+        val master = event(1, uid = "abc@example.org", end = null, duration = "P3600S", rrule = "FREQ=DAILY")
+        val moved = event(2, start = oct9 + 26 * hour, end = oct9 + 27 * hour, originalId = 1,
+                          originalTime = oct9 + 24 * hour)
+        val e = events(lines(master, moved))
+        assertEquals("UID:abc@example.org", e[0].prop("UID"))
+        assertEquals("UID:abc@example.org", e[1].prop("UID"))
+        assertEquals("RECURRENCE-ID;TZID=Europe/Paris:20261010T140000", e[1].prop("RECURRENCE-ID"))
+    }
+
+    @Test fun `text is escaped and long lines folded without splitting a character`() {
+        val desc = "a;b,c\\d\nsecond line " + "é".repeat(60) + " 🎉".repeat(20)
+        val l = lines(event(1, description = desc))
+        assertTrue(l.all { it.toByteArray(Charsets.UTF_8).size <= 75 })
+        val e = events(l)[0]
+        assertEquals("DESCRIPTION:" + "a\\;b\\,c\\\\d\\nsecond line " + "é".repeat(60) + " 🎉".repeat(20),
+                     e.prop("DESCRIPTION"))
+    }
+
+    @Test fun `reminders, attendees and a cancelled status come along`() {
+        val e = events(lines(event(1, status = 2, reminders = listOf(10, 10, 60),
+                                   attendees = listOf(Attendee("ada@example.org", "Ada, L.")))))[0]
+        assertEquals("STATUS:CANCELLED", e.prop("STATUS"))
+        assertEquals(listOf("TRIGGER:-PT10M", "TRIGGER:-PT60M"), e.filter { it.startsWith("TRIGGER") })
+        assertEquals("ATTENDEE;CN=\"Ada, L.\":mailto:ada@example.org", e.prop("ATTENDEE"))
+        assertEquals("X-MESHBAY-CALENDAR:Personal", e.prop("X-MESHBAY-CALENDAR"))
+    }
+}