From bbee80dbd0a43809221f2de0f0070f8c6df7aee6 Mon Sep 17 00:00:00 2001
From: ravi-signal <99042880+ravi-signal@users.noreply.github.com>
Date: Thu, 29 May 2025 18:14:23 -0500
Subject: [PATCH] Fix class cast exceptions with SchedulingUtil

---
 .../scheduler/SchedulingUtil.java             | 25 ++++++++++--
 .../scheduler/SchedulingUtilTest.java         | 39 +++++++++++++++++++
 2 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtil.java b/service/src/main/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtil.java
index 579dc0391..e1c688d6b 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtil.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtil.java
@@ -5,16 +5,21 @@ import com.google.i18n.phonenumbers.NumberParseException;
 import com.google.i18n.phonenumbers.PhoneNumberToTimeZonesMapper;
 import com.google.i18n.phonenumbers.PhoneNumberUtil;
 import com.google.i18n.phonenumbers.Phonenumber;
-import org.whispersystems.textsecuregcm.storage.Account;
 import java.time.Clock;
 import java.time.Instant;
 import java.time.LocalTime;
 import java.time.ZoneId;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
+import java.time.zone.ZoneRules;
+import java.util.Comparator;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import org.whispersystems.textsecuregcm.storage.Account;
 
 public class SchedulingUtil {
 
@@ -70,7 +75,10 @@ public class SchedulingUtil {
         return Optional.empty();
       }
 
-      final List<ZoneId> sortedZoneOffsets = timeZonesForNumber
+      final Instant now = clock.instant();
+
+      // Consider each unique ZoneRules and pick an arbitrary representative ZoneId for it
+      final Map<ZoneRules, ZoneId> byOffset = timeZonesForNumber
           .stream()
           .map(id -> {
             try {
@@ -80,10 +88,19 @@ public class SchedulingUtil {
             }
           })
           .filter(Objects::nonNull)
-          .sorted()
+          .collect(Collectors.toMap(
+              ZoneId::getRules,
+              Function.identity(),
+              (v1, v2) -> v2));
+
+      // Sort the ZoneRules by the offsets they produce
+      final List<ZoneRules> zoneRulesSortedByOffset = byOffset.keySet()
+          .stream()
+          .sorted(Comparator.comparing(z -> z.getOffset(now)))
           .toList();
 
-      return Optional.of(sortedZoneOffsets.get(sortedZoneOffsets.size() / 2));
+      // Select the "middle" ZoneRule and return one of the ZoneIds that have that ZoneRule
+      return Optional.of(byOffset.get(zoneRulesSortedByOffset.get(zoneRulesSortedByOffset.size() / 2)));
     } catch (final NumberParseException e) {
       return Optional.empty();
     }
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtilTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtilTest.java
index ee7631d62..ee95cc976 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtilTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/scheduler/SchedulingUtilTest.java
@@ -4,16 +4,23 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
+import com.google.i18n.phonenumbers.PhoneNumberToTimeZonesMapper;
 import com.google.i18n.phonenumbers.PhoneNumberUtil;
 import java.time.Clock;
+import java.time.Instant;
 import java.time.LocalDateTime;
 import java.time.LocalTime;
 import java.time.ZoneId;
 import java.time.ZoneOffset;
 import java.time.ZonedDateTime;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import com.google.i18n.phonenumbers.Phonenumber;
 import org.junit.jupiter.api.Test;
 import org.whispersystems.textsecuregcm.storage.Account;
 import org.whispersystems.textsecuregcm.storage.Device;
+import org.whispersystems.textsecuregcm.util.TestClock;
 
 class SchedulingUtilTest {
 
@@ -89,4 +96,36 @@ class SchedulingUtilTest {
         SchedulingUtil.getNextRecommendedNotificationTime(account, LocalTime.of(14, 0),
             Clock.fixed(afterNotificationTime.toInstant(berlineZoneOffset), berlinZoneId)));
   }
+
+  @Test
+  void zoneIdSelectionSingleOffset() {
+    final Account account = mock(Account.class);
+    final Phonenumber.PhoneNumber phoneNumber = PhoneNumberUtil.getInstance().getExampleNumber("DE");
+
+    when(account.getNumber())
+        .thenReturn(PhoneNumberUtil.getInstance().format(phoneNumber , PhoneNumberUtil.PhoneNumberFormat.E164));
+
+    final Instant now = Instant.now();
+
+    assertEquals(
+        ZoneId.of("Europe/Berlin").getRules().getOffset(now),
+        SchedulingUtil.getZoneId(account, TestClock.pinned(now)).orElseThrow().getRules().getOffset(now));
+  }
+
+  @Test
+  void zoneIdSelectionMultipleOffsets() {
+    final Account account = mock(Account.class);
+
+    // A US VOIP number spans multiple time zones, we should pick a 'middle' one
+    final Phonenumber.PhoneNumber phoneNumber =
+        PhoneNumberUtil.getInstance().getExampleNumberForType("US", PhoneNumberUtil.PhoneNumberType.VOIP);
+    when(account.getNumber())
+        .thenReturn(PhoneNumberUtil.getInstance().format(phoneNumber, PhoneNumberUtil.PhoneNumberFormat.E164));
+
+    final Instant now = Instant.now();
+
+    assertEquals(
+        ZoneId.of("America/Chicago").getRules().getOffset(now),
+        SchedulingUtil.getZoneId(account, TestClock.pinned(now)).orElseThrow().getRules().getOffset(now));
+  }
 }