fix(reminders): show the day for reminders on another day (#46)

A reminder fired ahead of an event on a different day showed only the
event's time (e.g. "09:30 – 10:00"), making it look like it was
happening today. reminderTimeText now prefixes timed events with a
relative day: "Tomorrow"/"Yesterday", the short weekday for another day
this week, or the exact date for anything further out.

The this-week boundary honours the user's "week starts on" setting: the
resolved first day of week is threaded through from ReminderNotifier, so
e.g. a Sunday reads as next week under a Sunday-start locale. All-day
events keep their explicit date (never ambiguous), and cross-midnight
timed events keep both explicit dates.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/test/java/de/jeanlucmakiola/calendula/data/reminders/ReminderTimeTextTest.kt

@@ -2,6 +2,7 @@ package de.jeanlucmakiola.calendula.data.reminders
 
 import com.google.common.truth.Truth.assertThat
 import org.junit.jupiter.api.Test
+import java.time.DayOfWeek
 import java.time.LocalDate
 import java.time.LocalDateTime
 import java.time.ZoneId
@@ -18,41 +19,110 @@ class ReminderTimeTextTest {
     private fun utcMidnight(date: LocalDate): Long =
         date.atStartOfDay(ZoneOffset.UTC).toInstant().toEpochMilli()
 
+    /** Wrapper defaulting `today` to the event's own begin day, so unrelated tests read "today". */
+    private fun text(
+        beginMillis: Long,
+        endMillis: Long,
+        isAllDay: Boolean = false,
+        zone: ZoneId = berlin,
+        locale: Locale = Locale.GERMANY,
+        is24Hour: Boolean = true,
+        today: LocalDate? = null,
+        firstDayOfWeek: DayOfWeek = DayOfWeek.MONDAY,
+    ): String = reminderTimeText(
+        beginMillis = beginMillis,
+        endMillis = endMillis,
+        isAllDay = isAllDay,
+        zone = zone,
+        locale = locale,
+        is24Hour = is24Hour,
+        today = today ?: java.time.Instant.ofEpochMilli(beginMillis).atZone(zone).toLocalDate(),
+        firstDayOfWeek = firstDayOfWeek,
+        tomorrowLabel = "Tomorrow",
+        yesterdayLabel = "Yesterday",
+    )
+
     @Test
-    fun `timed event on one day shows just the time range`() {
-        val text = reminderTimeText(
+    fun `timed event today shows just the time range`() {
+        val text = text(
             beginMillis = millisAt(LocalDateTime.of(2026, 6, 11, 9, 30), berlin),
             endMillis = millisAt(LocalDateTime.of(2026, 6, 11, 10, 0), berlin),
-            isAllDay = false,
-            zone = berlin,
-            locale = Locale.GERMANY,
-            is24Hour = true,
         )
         assertThat(text).isEqualTo("09:30 – 10:00")
     }
 
     @Test
     fun `12-hour preference renders an am-pm time range`() {
-        val text = reminderTimeText(
+        val text = text(
             beginMillis = millisAt(LocalDateTime.of(2026, 6, 11, 14, 0), berlin),
             endMillis = millisAt(LocalDateTime.of(2026, 6, 11, 15, 0), berlin),
-            isAllDay = false,
-            zone = berlin,
             locale = Locale.US,
             is24Hour = false,
         )
         assertThat(text).isEqualTo("2:00 PM – 3:00 PM")
     }
 
+    @Test
+    fun `tomorrow's event is prefixed with the tomorrow label`() {
+        val text = text(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 12, 9, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 12, 10, 0), berlin),
+            today = LocalDate.of(2026, 6, 11),
+        )
+        assertThat(text).isEqualTo("Tomorrow, 09:30 – 10:00")
+    }
+
+    @Test
+    fun `yesterday's event is prefixed with the yesterday label`() {
+        val text = text(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 10, 9, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 10, 10, 0), berlin),
+            today = LocalDate.of(2026, 6, 11),
+        )
+        assertThat(text).isEqualTo("Yesterday, 09:30 – 10:00")
+    }
+
+    @Test
+    fun `an event later this week is prefixed with the short weekday`() {
+        // 2026-06-11 is a Thursday; +3 days lands on Sunday, still this (Mon-based) week.
+        val text = text(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 14, 9, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 14, 10, 0), berlin),
+            today = LocalDate.of(2026, 6, 11),
+        )
+        assertThat(text).isEqualTo("So., 09:30 – 10:00")
+    }
+
+    @Test
+    fun `the week boundary honours the week-start setting`() {
+        // Today Thu 2026-06-11, event Sun 2026-06-14. With a Sunday-start week the
+        // Thursday's week runs Sun 06-07..Sat 06-13, so 06-14 is already next week
+        // and must render as a date — the opposite of the Monday-start case above.
+        val text = text(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 14, 9, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 14, 10, 0), berlin),
+            today = LocalDate.of(2026, 6, 11),
+            firstDayOfWeek = DayOfWeek.SUNDAY,
+        )
+        assertThat(text).isEqualTo("14.06.2026, 09:30 – 10:00")
+    }
+
+    @Test
+    fun `an event next week falls back to the exact date, not a weekday`() {
+        // 2026-06-15 is the following Monday — a weekday alone would be ambiguous.
+        val text = text(
+            beginMillis = millisAt(LocalDateTime.of(2026, 6, 15, 9, 30), berlin),
+            endMillis = millisAt(LocalDateTime.of(2026, 6, 15, 10, 0), berlin),
+            today = LocalDate.of(2026, 6, 11),
+        )
+        assertThat(text).isEqualTo("15.06.2026, 09:30 – 10:00")
+    }
+
     @Test
     fun `timed event crossing midnight includes both dates`() {
-        val text = reminderTimeText(
+        val text = text(
             beginMillis = millisAt(LocalDateTime.of(2026, 6, 11, 23, 30), berlin),
             endMillis = millisAt(LocalDateTime.of(2026, 6, 12, 0, 30), berlin),
-            isAllDay = false,
-            zone = berlin,
-            locale = Locale.GERMANY,
-            is24Hour = true,
         )
         assertThat(text).contains("11.06.2026")
         assertThat(text).contains("12.06.2026")
@@ -61,28 +131,35 @@ class ReminderTimeTextTest {
 
     @Test
     fun `all-day single day shows one date, read in UTC`() {
-        val text = reminderTimeText(
+        val text = text(
             beginMillis = utcMidnight(LocalDate.of(2026, 6, 11)),
             endMillis = utcMidnight(LocalDate.of(2026, 6, 12)),
             isAllDay = true,
             // Zone must not matter for all-day events: UTC midnight is
             // 02:00 in Berlin — naive local reading would shift the day.
-            zone = berlin,
-            locale = Locale.GERMANY,
-            is24Hour = true,
+            today = LocalDate.of(2026, 6, 11),
         )
         assertThat(text).isEqualTo("11.06.2026")
     }
 
+    @Test
+    fun `all-day event tomorrow still shows the exact date, no relative prefix`() {
+        val text = text(
+            beginMillis = utcMidnight(LocalDate.of(2026, 6, 12)),
+            endMillis = utcMidnight(LocalDate.of(2026, 6, 13)),
+            isAllDay = true,
+            today = LocalDate.of(2026, 6, 11),
+        )
+        assertThat(text).isEqualTo("12.06.2026")
+    }
+
     @Test
     fun `all-day multi-day shows the last covered day, not the exclusive end`() {
-        val text = reminderTimeText(
+        val text = text(
             beginMillis = utcMidnight(LocalDate.of(2026, 6, 11)),
             endMillis = utcMidnight(LocalDate.of(2026, 6, 13)),
             isAllDay = true,
-            zone = berlin,
-            locale = Locale.GERMANY,
-            is24Hour = true,
+            today = LocalDate.of(2026, 6, 11),
         )
         assertThat(text).isEqualTo("11.06.2026 – 12.06.2026")
     }
@@ -90,13 +167,11 @@ class ReminderTimeTextTest {
     @Test
     fun `degenerate all-day range never renders an inverted span`() {
         val day = utcMidnight(LocalDate.of(2026, 6, 11))
-        val text = reminderTimeText(
+        val text = text(
             beginMillis = day,
             endMillis = day,
             isAllDay = true,
-            zone = berlin,
-            locale = Locale.GERMANY,
-            is24Hour = true,
+            today = LocalDate.of(2026, 6, 11),
         )
         assertThat(text).isEqualTo("11.06.2026")
     }