feat(calendars): "Add to phone calendar" intent + multi-day bars in month grid

- New IconButton in the detail screen opens the system event composer (Google Calendar / Samsung / iCloud) pre-filled with title, range, location, and description via Intent.ACTION_INSERT on CalendarContract. Falls back to the .ics share path if no calendar app is installed. - Replaced the per-cell event-dot row with horizontal bars that span the cells a multi-day event covers. Bars are laid out by a greedy lowest-lane assignment so overlapping events stack rather than collide; cells removed their horizontal padding so adjacent bars merge into one uninterrupted line. - Bars round their ends only at the event's actual start/end (or at week boundaries), so a 3-day conference reads as one continuous pill across the row. - Added MonthGridBarsTest (7 tests) covering single/multi-day, lane collision, longer-event tiebreak, and the empty/ghost edge cases.
2026-05-19 19:51:01 +00:00
parent 971e9e4846
commit ab5d884b34
7 changed files with 431 additions and 33 deletions
@@ -0,0 +1,103 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars
+
+import android.content.ActivityNotFoundException
+import android.content.Context
+import android.content.Intent
+import android.provider.CalendarContract
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.parseIsoDateToUnixSeconds
+import com.vitorpamplona.quartz.nip01Core.core.Event
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import com.vitorpamplona.quartz.nip52Calendar.appt.time.CalendarTimeSlotEvent
+
+/**
+ * Opens the system "New Event" composer (Google Calendar / Samsung / iCloud / etc.) pre-populated
+ * with this appointment's title, time, location, and description. The user sees their normal
+ * calendar UI with one tap to "Save" — strictly nicer than the .ics-via-share-sheet path because
+ * it doesn't go through a file and surfaces the user's preferred calendar app directly.
+ *
+ * Returns true if a calendar app handled the intent, false if no handler was found — the caller
+ * can decide whether to fall back to the .ics share path.
+ */
+fun addToPhoneCalendar(
+    context: Context,
+    event: Event,
+): Boolean {
+    val (title, location, summary) =
+        when (event) {
+            is CalendarTimeSlotEvent -> Triple(event.title(), event.location(), event.summary())
+            is CalendarDateSlotEvent -> Triple(event.title(), event.location(), event.summary())
+            else -> return false
+        }
+    val (beginMs, endMs, allDay) = computeRangeMs(event) ?: return false
+
+    val description =
+        buildString {
+            summary?.let { append(it) }
+            if (event.content.isNotBlank()) {
+                if (isNotEmpty()) append("\n\n")
+                append(event.content)
+            }
+        }
+
+    val intent =
+        Intent(Intent.ACTION_INSERT).apply {
+            data = CalendarContract.Events.CONTENT_URI
+            putExtra(CalendarContract.Events.TITLE, title.orEmpty())
+            location?.let { putExtra(CalendarContract.Events.EVENT_LOCATION, it) }
+            if (description.isNotEmpty()) {
+                putExtra(CalendarContract.Events.DESCRIPTION, description)
+            }
+            putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginMs)
+            putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endMs)
+            putExtra(CalendarContract.EXTRA_EVENT_ALL_DAY, allDay)
+            addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+        }
+
+    return try {
+        context.startActivity(intent)
+        true
+    } catch (_: ActivityNotFoundException) {
+        false
+    }
+}
+
+/**
+ * Computes the (beginMillis, endMillis, isAllDay) triple from a calendar event. NIP-52 date-slot
+ * uses ISO dates that we anchor at local midnight; time-slot uses unix seconds. End defaults to
+ * begin + 1 hour for time-slot events without an end and to begin + 1 day for all-day events
+ * without an end (calendar providers expect end > start for any visible event).
+ */
+private fun computeRangeMs(event: Event): Triple<Long, Long, Boolean>? =
+    when (event) {
+        is CalendarTimeSlotEvent -> {
+            val start = event.start() ?: return null
+            val end = event.end() ?: (start + 3600L)
+            Triple(start * 1000L, end * 1000L, false)
+        }
+        is CalendarDateSlotEvent -> {
+            val startSec = parseIsoDateToUnixSeconds(event.start()) ?: return null
+            val endSec = parseIsoDateToUnixSeconds(event.end()) ?: (startSec + 86400L)
+            Triple(startSec * 1000L, endSec * 1000L, true)
+        }
+        else -> null
+    }
@@ -32,10 +32,8 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
-import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
@@ -48,7 +46,6 @@ import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
@@ -56,9 +53,11 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.ui.feeds.FeedContentState
 import com.vitorpamplona.amethyst.commons.ui.feeds.FeedState
-import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.ui.navigation.navs.INav
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.MONTH_GRID_MAX_LANES
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.MonthGridBarSegment
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.computeMonthGridBars
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.groupByDayKeyExpanded
 import com.vitorpamplona.amethyst.ui.stringRes
 import java.time.LocalDate
@@ -94,6 +93,7 @@ fun CalendarMonthView(
    }

    val eventsByDay by remember(notes) { derivedStateOf { groupByDayKeyExpanded(notes) } }
+    val barsByDay by remember(notes) { derivedStateOf { computeMonthGridBars(notes) } }

    var selectedDayKey by rememberSaveable { mutableStateOf<Long?>(null) }

@@ -136,7 +136,7 @@ fun CalendarMonthView(
        MonthGrid(
            visibleMonth = visibleMonth,
            today = today,
-            eventsByDay = eventsByDay,
+            barsByDay = barsByDay,
            selectedDayKey = selectedDayKey,
            onDayClick = { dayKey ->
                selectedDayKey = if (selectedDayKey == dayKey) null else dayKey
@@ -176,7 +176,7 @@ private fun WeekdayHeader() {
 private fun MonthGrid(
    visibleMonth: YearMonth,
    today: LocalDate,
-    eventsByDay: Map<Long, List<Note>>,
+    barsByDay: Map<Long, List<MonthGridBarSegment>>,
    selectedDayKey: Long?,
    onDayClick: (Long) -> Unit,
 ) {
@@ -196,16 +196,22 @@ private fun MonthGrid(
                    if (dayNumber in 1..daysInMonth) {
                        val date = visibleMonth.atDay(dayNumber)
                        val dayKey = date.toEpochDay()
+                        val cellBars = barsByDay[dayKey].orEmpty()
                        DayCell(
                            modifier = Modifier.weight(1f),
                            dayNumber = dayNumber,
                            isToday = isCurrentMonth && date == today,
                            isSelected = selectedDayKey == dayKey,
-                            eventCount = eventsByDay[dayKey]?.size ?: 0,
+                            bars = cellBars,
+                            // Anything past the visible lane cap collapses into a "+N" tail —
+                            // keeps each cell readable when a day has more than three events.
+                            extraEventCount = cellBars.count { it.lane >= MONTH_GRID_MAX_LANES },
+                            isWeekStart = c == 0,
+                            isWeekEnd = c == 6,
                            onClick = { onDayClick(dayKey) },
                        )
                    } else {
-                        Box(modifier = Modifier.weight(1f).height(56.dp))
+                        Box(modifier = Modifier.weight(1f).height(MONTH_CELL_HEIGHT))
                    }
                }
            }
@@ -213,13 +219,18 @@ private fun MonthGrid(
    }
 }

+private val MONTH_CELL_HEIGHT = 72.dp
+
@Composable
 private fun DayCell(
    modifier: Modifier,
    dayNumber: Int,
    isToday: Boolean,
    isSelected: Boolean,
-    eventCount: Int,
+    bars: List<MonthGridBarSegment>,
+    extraEventCount: Int,
+    isWeekStart: Boolean,
+    isWeekEnd: Boolean,
    onClick: () -> Unit,
 ) {
    val bg =
@@ -232,8 +243,11 @@ private fun DayCell(
    Box(
        modifier =
            modifier
-                .height(56.dp)
-                .padding(2.dp)
+                .height(MONTH_CELL_HEIGHT)
+                // Vertical-only padding so adjacent cells in a row touch horizontally — a
+                // multi-day bar that extends from the right edge of one cell to the left edge of
+                // the next visually merges into a single uninterrupted line.
+                .padding(vertical = 2.dp)
                .background(bg, RoundedCornerShape(8.dp))
                .border(
                    width = if (isToday) 1.5.dp else 0.5.dp,
@@ -242,9 +256,8 @@ private fun DayCell(
                ).clickable(onClick = onClick),
    ) {
        Column(
-            modifier = Modifier.fillMaxSize().padding(4.dp),
+            modifier = Modifier.fillMaxSize().padding(horizontal = 2.dp, vertical = 4.dp),
            horizontalAlignment = Alignment.CenterHorizontally,
-            verticalArrangement = Arrangement.SpaceBetween,
        ) {
            Text(
                text = dayNumber.toString(),
@@ -257,35 +270,69 @@ private fun DayCell(
                        MaterialTheme.colorScheme.onSurface
                    },
            )
-            EventDotRow(eventCount)
+            Spacer(modifier = Modifier.height(2.dp))
+            EventBarLanes(
+                bars = bars,
+                extraEventCount = extraEventCount,
+                isWeekStart = isWeekStart,
+                isWeekEnd = isWeekEnd,
+            )
        }
    }
 }

+/**
+ * Renders up to [MONTH_GRID_MAX_LANES] horizontal bars stacked vertically. Each lane occupies a
+ * fixed height across every cell so a multi-day event sits on the same y-row in every column it
+ * covers — the visual continuity that makes "spans 3 days" readable at a glance.
+ *
+ * The bar is rounded only at the event's start (`isLeftEnd`) and end (`isRightEnd`). On week
+ * boundaries we also round so each row of the grid looks self-contained instead of bleeding into
+ * an unaligned next row.
+ */
@Composable
-private fun EventDotRow(eventCount: Int) {
-    if (eventCount <= 0) {
-        Spacer(modifier = Modifier.height(6.dp))
-        return
-    }
-    Row(
-        horizontalArrangement = Arrangement.spacedBy(2.dp),
-        modifier = Modifier.padding(bottom = 1.dp),
+private fun EventBarLanes(
+    bars: List<MonthGridBarSegment>,
+    extraEventCount: Int,
+    isWeekStart: Boolean,
+    isWeekEnd: Boolean,
 ) {
-        repeat(eventCount.coerceAtMost(3)) {
+    val barColor = MaterialTheme.colorScheme.primary
+    Column(
+        modifier = Modifier.fillMaxWidth(),
+        verticalArrangement = Arrangement.spacedBy(1.dp),
+    ) {
+        for (i in 0 until MONTH_GRID_MAX_LANES) {
+            val seg = bars.firstOrNull { it.lane == i }
+            if (seg != null) {
+                val roundLeft = seg.isLeftEnd || isWeekStart
+                val roundRight = seg.isRightEnd || isWeekEnd
                Box(
                    modifier =
                        Modifier
-                        .size(5.dp)
-                        .background(MaterialTheme.colorScheme.primary, CircleShape),
+                            .fillMaxWidth()
+                            .height(5.dp)
+                            .background(
+                                color = barColor,
+                                shape =
+                                    RoundedCornerShape(
+                                        topStart = if (roundLeft) 2.dp else 0.dp,
+                                        bottomStart = if (roundLeft) 2.dp else 0.dp,
+                                        topEnd = if (roundRight) 2.dp else 0.dp,
+                                        bottomEnd = if (roundRight) 2.dp else 0.dp,
+                                    ),
+                            ),
                )
+            } else {
+                Spacer(modifier = Modifier.fillMaxWidth().height(5.dp))
            }
-        if (eventCount > 3) {
+        }
+        if (extraEventCount > 0) {
            Text(
-                text = "+",
+                text = "+$extraEventCount",
                style = MaterialTheme.typography.labelSmall,
-                color = MaterialTheme.colorScheme.primary,
-                modifier = Modifier.graphicsLayer { translationY = -3f },
+                color = barColor,
+                fontWeight = FontWeight.SemiBold,
            )
        }
    }
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal
+
+import androidx.compose.runtime.Immutable
+import com.vitorpamplona.amethyst.model.Note
+
+/**
+ * One bar drawn into one day cell, with `lane` controlling its vertical position so two
+ * overlapping multi-day events stack rather than collide. `isLeftEnd` / `isRightEnd` control
+ * which corners of the bar are rounded — a continuation day in the middle of a 3-day event gets
+ * neither end rounded, so adjacent cells visually merge into one bar.
+ *
+ * Note: the underlying [Note] is exposed so the UI can colour or label bars per event. Equality
+ * is on idHex so a row of cells holding the same bar share segment identity for keys.
+ */
+@Immutable
+data class MonthGridBarSegment(
+    val note: Note,
+    val lane: Int,
+    val isLeftEnd: Boolean,
+    val isRightEnd: Boolean,
+)
+
+/**
+ * Maximum lanes we render before collapsing the remainder into a "+N" overflow label. Three
+ * matches the previous dot-row capacity and keeps each 56dp cell readable on mid-range phones.
+ */
+const val MONTH_GRID_MAX_LANES = 3
+
+/**
+ * Greedy lane-assignment for the month grid: sort events earliest-start-first (longer events
+ * wins ties so they take the top lane), then for each event pick the lowest lane index whose
+ * full day-range is unoccupied. Returns a per-day-key map so each cell can render its own
+ * segments without re-running the layout.
+ *
+ * Single-day events participate in the same layout — they get bars too, just short ones,
+ * which keeps the visual language consistent.
+ */
+fun computeMonthGridBars(notes: List<Note>): Map<Long, List<MonthGridBarSegment>> {
+    val ranges =
+        notes
+            .distinctBy { it.idHex }
+            .mapNotNull { n -> n.calendarLocalDayKeyRange()?.let { n to it } }
+            .sortedWith(
+                compareBy(
+                    { it.second.first },
+                    { -(it.second.last - it.second.first) },
+                    { it.first.idHex },
+                ),
+            )
+
+    // day-key → set of lanes already claimed for that day
+    val occupied = mutableMapOf<Long, MutableSet<Int>>()
+    val perDay = mutableMapOf<Long, MutableList<MonthGridBarSegment>>()
+
+    for ((note, range) in ranges) {
+        // Find the lowest lane index whose full range is free. Bounded at 32 so a pathological
+        // input can't loop forever; overflow events still render as "+N" via the cap downstream.
+        var lane = 0
+        while (lane < 32) {
+            val clash = (range).any { occupied[it]?.contains(lane) == true }
+            if (!clash) break
+            lane++
+        }
+        for (day in range) {
+            occupied.getOrPut(day) { mutableSetOf() }.add(lane)
+            perDay.getOrPut(day) { mutableListOf() }.add(
+                MonthGridBarSegment(
+                    note = note,
+                    lane = lane,
+                    isLeftEnd = day == range.first,
+                    isRightEnd = day == range.last,
+                ),
+            )
+        }
+    }
+    // Within each cell, sort by lane so the rendering doesn't have to.
+    return perDay.mapValues { (_, list) -> list.sortedBy { it.lane } }
+}
@@ -72,6 +72,7 @@ import com.vitorpamplona.amethyst.ui.note.ReactionsRow
 import com.vitorpamplona.amethyst.ui.note.UsernameDisplay
 import com.vitorpamplona.amethyst.ui.note.types.CalendarRsvpRow
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.addToPhoneCalendar
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.IcsExport
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.appointmentView
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.datasource.CalendarsFilterAssemblerSubscription
@@ -153,6 +154,24 @@ fun CalendarEventDetailScreen(
                    //    in posts, in other clients). A single button with a chooser would be
                    //    cleaner, but two icons keep both actions one tap away.
                    if (event != null) {
+                        // Direct "Add to phone calendar" — opens the system event composer with
+                        // every field pre-filled. Falls back to the .ics share path if the device
+                        // has no calendar app registered for ACTION_INSERT (rare; Wear OS, some
+                        // GrapheneOS profiles).
+                        IconButton(onClick = {
+                            if (!addToPhoneCalendar(context, event)) {
+                                val ics = IcsExport.appointmentToIcs(event, targetAddress, TimeUtils.now())
+                                val filename = IcsExport.appointmentFilename(event, targetAddress)
+                                shareIcs(context, filename, ics)
+                            }
+                        }) {
+                            Icon(
+                                symbol = MaterialSymbols.EventAvailable,
+                                contentDescription = stringRes(R.string.calendar_add_to_phone_calendar),
+                                modifier = Modifier.size(20.dp),
+                                tint = MaterialTheme.colorScheme.onSurface,
+                            )
+                        }
                        IconButton(onClick = {
                            val ics = IcsExport.appointmentToIcs(event, targetAddress, TimeUtils.now())
                            val filename = IcsExport.appointmentFilename(event, targetAddress)
@@ -1968,6 +1968,7 @@
    <string name="calendar_no_events">No events</string>
    <string name="calendar_continues">Continues</string>
    <string name="calendar_day_of_total">Day %1$d of %2$d</string>
+    <string name="calendar_add_to_phone_calendar">Add to phone calendar</string>
    <string name="calendar_untitled">(untitled)</string>
    <string name="calendar_all_day">All-day</string>
    <string name="calendar_rsvp_going_prefixed">✓ Going</string>
@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.calendar
+
+import com.vitorpamplona.amethyst.model.Note
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.calendars.dal.computeMonthGridBars
+import com.vitorpamplona.quartz.nip52Calendar.appt.day.CalendarDateSlotEvent
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.time.LocalDate
+
+class MonthGridBarsTest {
+    @Test
+    fun singleDayEvent_oneSegment_bothEndsRounded() {
+        val note = dateSlot("a", "2025-01-15")
+        val key = LocalDate.of(2025, 1, 15).toEpochDay()
+        val byDay = computeMonthGridBars(listOf(note))
+        val seg = byDay[key]?.single()
+        assertNotNull(seg)
+        assertTrue("single-day event should round both ends", seg!!.isLeftEnd && seg.isRightEnd)
+        assertEquals(0, seg.lane)
+    }
+
+    @Test
+    fun threeDayEvent_segmentPerDay_endsOnlyOnBoundaries() {
+        val note = dateSlot("a", "2025-01-15", end = "2025-01-17")
+        val byDay = computeMonthGridBars(listOf(note))
+        val k15 = LocalDate.of(2025, 1, 15).toEpochDay()
+        val k16 = LocalDate.of(2025, 1, 16).toEpochDay()
+        val k17 = LocalDate.of(2025, 1, 17).toEpochDay()
+        assertEquals(true to false, byDay[k15]!!.single().run { isLeftEnd to isRightEnd })
+        assertEquals(false to false, byDay[k16]!!.single().run { isLeftEnd to isRightEnd })
+        assertEquals(false to true, byDay[k17]!!.single().run { isLeftEnd to isRightEnd })
+    }
+
+    @Test
+    fun overlappingEvents_assignedToDistinctLanes() {
+        // A: Jan 15–17. B: Jan 16–18. They overlap on 16 and 17 so must land in different lanes.
+        val a = dateSlot("a", "2025-01-15", end = "2025-01-17")
+        val b = dateSlot("b", "2025-01-16", end = "2025-01-18")
+        val byDay = computeMonthGridBars(listOf(a, b))
+        val k16 = LocalDate.of(2025, 1, 16).toEpochDay()
+        val lanes = byDay[k16]!!.map { it.lane }.toSet()
+        assertEquals("expected two distinct lanes on the overlap day", 2, lanes.size)
+    }
+
+    @Test
+    fun longerEventTakesLowerLane_amongTies() {
+        // Earliest-start ties broken by length-descending: the longer event sits on lane 0 so it
+        // visually anchors the top, with the shorter one tucked under it.
+        val long3 = dateSlot("L", "2025-01-15", end = "2025-01-17")
+        val short1 = dateSlot("S", "2025-01-15")
+        val byDay = computeMonthGridBars(listOf(short1, long3))
+        val k15 = byDay[LocalDate.of(2025, 1, 15).toEpochDay()]!!
+        val longLane = k15.first { it.note === long3 }.lane
+        val shortLane = k15.first { it.note === short1 }.lane
+        assertTrue("longer event should be in a lower lane", longLane < shortLane)
+    }
+
+    @Test
+    fun nonOverlappingEvents_reuseLowestLane() {
+        // A: Jan 15. B: Jan 16. C: Jan 17. No overlaps → all on lane 0.
+        val a = dateSlot("a", "2025-01-15")
+        val b = dateSlot("b", "2025-01-16")
+        val c = dateSlot("c", "2025-01-17")
+        val byDay = computeMonthGridBars(listOf(a, b, c))
+        for (note in listOf(a, b, c)) {
+            val key =
+                note.event!!
+                    .tags
+                    .first { it[0] == "start" }[1]
+                    .let(LocalDate::parse)
+                    .toEpochDay()
+            assertEquals(0, byDay[key]!!.single().lane)
+        }
+    }
+
+    @Test
+    fun noEvents_emptyMap() {
+        val byDay = computeMonthGridBars(emptyList())
+        assertTrue(byDay.isEmpty())
+    }
+
+    @Test
+    fun noteWithoutStart_dropped() {
+        val ghost = Note("ghost") // no event
+        val real = dateSlot("a", "2025-01-15")
+        val byDay = computeMonthGridBars(listOf(ghost, real))
+        assertEquals(1, byDay.size)
+        assertNull(byDay[0L])
+    }
+
+    private fun dateSlot(
+        id: String,
+        start: String,
+        end: String? = null,
+    ): Note {
+        val tags =
+            buildList {
+                add(arrayOf("d", "$id-d"))
+                add(arrayOf("title", "T"))
+                add(arrayOf("start", start))
+                end?.let { add(arrayOf("end", it)) }
+            }.toTypedArray()
+        val e = CalendarDateSlotEvent(id, "pub", 0L, tags, "", "sig")
+        return Note(id).apply { event = e }
+    }
+}
@@ -97,6 +97,7 @@ object MaterialSymbols {
    val EmojiEmotions = MaterialSymbol("\uEA22")
    val Error = MaterialSymbol("\uF8B6")
    val ErrorOutline = MaterialSymbol("\uF8B6")
+    val EventAvailable = MaterialSymbol("\uE614")
    val ExpandLess = MaterialSymbol("\uE5CE")
    val ExpandMore = MaterialSymbol("\uE5CF")
    val Explore = MaterialSymbol("\uE87A")