Introduce AndroidCompatTimeZoneRegistry (#60)

* androidify populated start times
* introduce AndroidCompatTimeZoneRegistry (closes #57, #58, #59)

6 files changed, 173 insertions, 0 deletions

diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidCompatTimeZoneRegistryTest.kt b/src/androidTest/java/at/bitfire/ical4android/AndroidCompatTimeZoneRegistryTest.kt
new file mode 100644
index 0000000..5958e16
--- /dev/null
+++ b/src/androidTest/java/at/bitfire/ical4android/AndroidCompatTimeZoneRegistryTest.kt
@@ -0,0 +1,70 @@
+/***************************************************************************************************
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ **************************************************************************************************/
+
+package at.bitfire.ical4android
+
+import net.fortuna.ical4j.model.DefaultTimeZoneRegistryFactory
+import net.fortuna.ical4j.model.TimeZoneRegistry
+import org.junit.Assert.*
+import org.junit.Assume
+import org.junit.Before
+import org.junit.Test
+import java.time.ZoneId
+import java.time.zone.ZoneRulesException
+
+class AndroidCompatTimeZoneRegistryTest {
+
+    lateinit var ical4jRegistry: TimeZoneRegistry
+    lateinit var registry: TimeZoneRegistry
+
+    val systemKnowsKyiv =
+        try {
+            ZoneId.of("Europe/Kyiv")
+            true
+        } catch (e: ZoneRulesException) {
+            false
+        }
+
+    @Before
+    fun createRegistry() {
+        ical4jRegistry = DefaultTimeZoneRegistryFactory.getInstance().createRegistry()
+        registry = AndroidCompatTimeZoneRegistry.Factory().createRegistry()
+    }
+
+
+    @Test
+    fun getTimeZone_Existing() {
+        assertEquals(
+            ical4jRegistry.getTimeZone("Europe/Vienna"),
+            registry.getTimeZone("Europe/Vienna")
+        )
+    }
+
+    @Test
+    fun getTimeZone_Existing_Kiev() {
+        Assume.assumeFalse(systemKnowsKyiv)
+        val tz = registry.getTimeZone("Europe/Kiev")
+        assertFalse(tz === ical4jRegistry.getTimeZone("Europe/Kiev"))      // we have made a copy
+        assertEquals("Europe/Kiev", tz?.id)
+        assertEquals("Europe/Kiev", tz?.vTimeZone?.timeZoneId?.value)
+    }
+
+    @Test
+    fun getTimeZone_Existing_Kyiv() {
+        Assume.assumeFalse(systemKnowsKyiv)
+
+        /* Unfortunately, AndroidCompatTimeZoneRegistry can't rewrite to Europy/Kyiv to anything because
+           it doesn't know a valid Android name for it. */
+        assertEquals(
+            ical4jRegistry.getTimeZone("Europe/Kyiv"),
+            registry.getTimeZone("Europe/Kyiv")
+        )
+    }
+
+    @Test
+    fun getTimeZone_NotExisting() {
+        assertNull(registry.getTimeZone("Test/NotExisting"))
+    }
+
+}
\ No newline at end of file
diff --git a/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt b/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt
index 556fa0b..cb094ca 100644
--- a/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt
+++ b/src/androidTest/java/at/bitfire/ical4android/AndroidEventTest.kt
@@ -29,6 +29,7 @@ import org.junit.Assert.*
 import java.net.URI
 import java.time.Duration
 import java.time.Period
+import java.util.TimeZone
 
 class AndroidEventTest {
 
@@ -1460,6 +1461,21 @@ class AndroidEventTest {
     }
 
     @Test
+    fun testPopulateEvent_NonAllDay_Recurring_Duration_KievTimeZone() {
+        populateEvent(false) {
+            put(Events.DTSTART, 1592733600000L)  // 21/06/2020 18:00 +0800
+            put(Events.EVENT_TIMEZONE, "Europe/Kiev")
+            put(Events.DURATION, "PT1H")
+            put(Events.RRULE, "FREQ=DAILY;COUNT=2")
+        }.let { result ->
+            assertEquals(1592733600000L, result.dtStart?.date?.time)
+            assertEquals(1592733600000L + 3600000, result.dtEnd?.date?.time)
+            assertEquals("Europe/Kiev", result.dtStart?.timeZone?.id)
+            assertEquals("Europe/Kiev", result.dtEnd?.timeZone?.id)
+        }
+    }
+
+    @Test
     fun testPopulateEvent_NonAllDay_NonRecurring_NoTime() {
         populateEvent(false) {
             put(Events.DTSTART, 1592742600000L)  // 21/06/2020 14:30 +0200
diff --git a/src/main/java/at/bitfire/ical4android/AndroidCompatTimeZoneRegistry.kt b/src/main/java/at/bitfire/ical4android/AndroidCompatTimeZoneRegistry.kt
new file mode 100644
index 0000000..5f7246d
--- /dev/null
+++ b/src/main/java/at/bitfire/ical4android/AndroidCompatTimeZoneRegistry.kt
@@ -0,0 +1,83 @@
+package at.bitfire.ical4android
+
+import net.fortuna.ical4j.model.*
+import net.fortuna.ical4j.model.component.VTimeZone
+import net.fortuna.ical4j.model.property.TzId
+import java.time.ZoneId
+
+/**
+ * The purpose of this class is that if a time zone has a different name in ical4j and Android,
+ * it should use the Android name.
+ *
+ * For instance, if a time zone is known as "Europe/Kyiv" (with alias "Europe/Kiev") in ical4j
+ * and only "Europe/Kiev" in Android, this registry behaves like the default [TimeZoneRegistryImpl],
+ * but the returned time zone for `getTimeZone("Europe/Kiev")` has an ID of "Europe/Kiev" and not
+ * "Europe/Kyiv".
+ */
+class AndroidCompatTimeZoneRegistry(
+    private val base: TimeZoneRegistry
+): TimeZoneRegistry by base {
+
+    /**
+     * Gets the time zone for a given ID.
+     *
+     * If a time zone with the given ID exists in Android, the icalj timezone for this ID
+     * is returned, but the TZID is set to the Android name (and not the ical4j name, which
+     * may not be known to Android).
+     *
+     * If a time zone with the given ID doesn't exist in Android, this method returns the
+     * result of its [base] method.
+     *
+     * @param id
+     * @return time zone
+     */
+    override fun getTimeZone(id: String): TimeZone? {
+        // check whether time zone is available on Android
+        val androidTzId =
+            try {
+                ZoneId.of(id).id
+            } catch (e: Exception) {
+                /* Not available in Android, should return null in a later version.
+                   However, we return the ical4j timezone to keep the changes caused by AndroidCompatTimeZoneRegistry introduction
+                   as small as possible. */
+                return base.getTimeZone(id)
+            }
+
+        /* Time zone known by Android. Unfortunately, we can't use the Android timezone database directly
+           to generate ical4j timezone definitions (which are based on VTIMEZONE).
+           So we have to use the timezone definition from ical4j (based on its own VTIMEZONE database),
+           but we also need to use the Android TZ name (otherwise Android may not understand it later).
+
+           Example: getTimeZone("Europe/Kiev") returns a TimeZone with TZID:Europe/Kyiv since ical4j/3.2.5,
+           but most Android devices don't now Europe/Kyiv yet.
+           */
+        val tz = base.getTimeZone(id)
+        if (tz.id != androidTzId) {
+            Ical4Android.log.warning("Using Android TZID $androidTzId instead of ical4j ${tz.id}")
+
+            // create a copy of the VTIMEZONE so that we don't modify the original registry values (which are not immutable)
+            val vTimeZone = tz.vTimeZone
+            val newVTimeZoneProperties = PropertyList(vTimeZone.properties)
+            newVTimeZoneProperties.removeAll { property ->
+                property is TzId
+            }
+            newVTimeZoneProperties += TzId(androidTzId)
+            return TimeZone(VTimeZone(
+                newVTimeZoneProperties,
+                vTimeZone.observances
+            ))
+        } else
+            return tz
+    }
+
+
+    class Factory : TimeZoneRegistryFactory() {
+
+        override fun createRegistry(): TimeZoneRegistry {
+            val ical4jRegistry = DefaultTimeZoneRegistryFactory().createRegistry()
+            return AndroidCompatTimeZoneRegistry(ical4jRegistry)
+        }
+
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/at/bitfire/ical4android/AndroidEvent.kt b/src/main/java/at/bitfire/ical4android/AndroidEvent.kt
index 8648dd5..7c354a6 100644
--- a/src/main/java/at/bitfire/ical4android/AndroidEvent.kt
+++ b/src/main/java/at/bitfire/ical4android/AndroidEvent.kt
@@ -228,6 +228,7 @@ abstract class AndroidEvent(
                 }
             }
             event.dtStart = DtStart(dtStartDateTime)
+            AndroidTimeUtils.androidifyTimeZone(event.dtStart)      // because it may have an ical4j timezone ID that is not available in Android
 
             // Android events MUST have duration or dtend [https://developer.android.com/reference/android/provider/CalendarContract.Events#operations].
             // Assume 1 hour if missing (should never occur, but occurs).
diff --git a/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt b/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt
index 337ab41..ec4388a 100644
--- a/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt
+++ b/src/main/java/at/bitfire/ical4android/util/AndroidTimeUtils.kt
@@ -104,6 +104,8 @@ object AndroidTimeUtils {
      * Returns the time-zone ID for a given date or date-time that should be used to store it
      * in the Android calendar provider.
      *
+     * Does not check whether Android actually knows the time zone ID – use [androidifyTimeZone] for that.
+     *
      * @param date DateProperty (DATE or DATE-TIME) whose time-zone information is used
      *
      * @return - UTC for dates and UTC date-times
diff --git a/src/main/resources/ical4j.properties b/src/main/resources/ical4j.properties
index dfa5830..5a83b9f 100644
--- a/src/main/resources/ical4j.properties
+++ b/src/main/resources/ical4j.properties
@@ -1,4 +1,5 @@
 net.fortuna.ical4j.timezone.cache.impl=net.fortuna.ical4j.util.MapTimeZoneCache
+net.fortuna.ical4j.timezone.registry=at.bitfire.ical4android.AndroidCompatTimeZoneRegistry$Factory
 net.fortuna.ical4j.timezone.update.enabled=false
 ical4j.parsing.relaxed=true
 ical4j.unfolding.relaxed=true