Add week/month view toggle with collapse animation and bottom card

Add isCollapsed/collapseProgress state to CalendarViewModel for toggling
between month and week views. CalendarMonthPage animates non-selected
weeks out with offset and alpha. Introduce WeekPager for single-week
HorizontalPager and BottomCard with drag-to-collapse gesture.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

shared/src/commonMain/kotlin/plus/rua/project/CalendarViewModel.kt

@@ -25,6 +25,12 @@ class CalendarViewModel {
     var selectedDate by mutableStateOf(today)
         private set
 
+    var isCollapsed by mutableStateOf(false)
+        private set
+
+    var collapseProgress by mutableStateOf(0f)
+        private set
+
     val currentYear: Int get() = selectedDate.year
     @Suppress("DEPRECATION")
     val currentMonth: Int get() = selectedDate.monthNumber
@@ -33,6 +39,16 @@ class CalendarViewModel {
         selectedDate = date
     }
 
+    fun collapse() {
+        isCollapsed = true
+        collapseProgress = 1f
+    }
+
+    fun expand() {
+        isCollapsed = false
+        collapseProgress = 0f
+    }
+
     fun getIsoWeekNumber(date: LocalDate): Int {
         val jan4 = LocalDate(date.year, 1, 4)
         val jan4DayOfWeek = jan4.dayOfWeek.ordinal

shared/src/commonMain/kotlin/plus/rua/project/ui/BottomCard.kt

@@ -0,0 +1,58 @@
+package plus.rua.project.ui
+
+import androidx.compose.animation.core.animate
+import androidx.compose.foundation.background
+import androidx.compose.foundation.gestures.detectVerticalDragGestures
+import androidx.compose.foundation.layout.Box
+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.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Surface
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.input.pointer.pointerInput
+import androidx.compose.ui.unit.dp
+import kotlinx.coroutines.launch
+import plus.rua.project.CalendarViewModel
+
+@Composable
+fun BottomCard(
+    viewModel: CalendarViewModel,
+    modifier: Modifier = Modifier
+) {
+    val coroutineScope = rememberCoroutineScope()
+
+    Surface(
+        modifier = modifier
+            .fillMaxWidth()
+            .pointerInput(Unit) {
+                detectVerticalDragGestures { _, dragAmount ->
+                    if (dragAmount < 0 && !viewModel.isCollapsed) {
+                        viewModel.collapse()
+                    }
+                }
+            },
+        shape = RoundedCornerShape(topStart = 16.dp, topEnd = 16.dp),
+        color = MaterialTheme.colorScheme.surfaceVariant,
+        shadowElevation = 4.dp
+    ) {
+        Box(modifier = Modifier.fillMaxSize()) {
+            Box(
+                modifier = Modifier
+                    .align(Alignment.TopCenter)
+                    .padding(top = 8.dp, bottom = 8.dp)
+                    .clip(RoundedCornerShape(2.dp))
+                    .background(Color.Gray.copy(alpha = 0.4f))
+                    .fillMaxWidth(0.15f)
+                    .height(4.dp)
+            )
+        }
+    }
+}

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarMonthPage.kt

@@ -1,12 +1,15 @@
 package plus.rua.project.ui
 
+import androidx.compose.animation.core.animateFloatAsState
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.unit.dp
 import kotlinx.datetime.DatePeriod
 import kotlinx.datetime.LocalDate
@@ -20,18 +23,46 @@ fun CalendarMonthPage(
     selectedDate: LocalDate,
     today: LocalDate,
     onDateClick: (LocalDate) -> Unit,
+    collapseProgress: Float,
     modifier: Modifier = Modifier
 ) {
     val days = remember(year, month) {
         generateMonthDays(year, month)
     }
 
+    val weeks = days.chunked(7)
+    val selectedWeekIndex = remember(weeks, selectedDate) {
+        weeks.indexOfFirst { week -> week.any { it.date == selectedDate } }
+    }
+
     Column(modifier = modifier) {
-        days.chunked(7).forEach { week ->
+        weeks.forEachIndexed { weekIndex, week ->
+            val animatedProgress = animateFloatAsState(
+                targetValue = collapseProgress,
+                label = "collapse-$weekIndex"
+            ).value
+
+            val isAboveSelected = weekIndex < selectedWeekIndex
+            val isBelowSelected = weekIndex > selectedWeekIndex
+
+            val offsetY = when {
+                isAboveSelected -> -animatedProgress * 200f
+                isBelowSelected -> animatedProgress * 200f
+                else -> 0f
+            }
+
+            val alpha = when {
+                isAboveSelected || isBelowSelected -> 1f - animatedProgress
+                else -> 1f
+            }
+
+            if (alpha > 0.01f) {
                 Row(
                     modifier = Modifier
                         .fillMaxWidth()
                         .padding(vertical = 2.dp)
+                        .offset(y = offsetY.dp)
+                        .alpha(alpha)
                 ) {
                     week.forEach { dayData ->
                         DayCell(
@@ -47,6 +78,7 @@ fun CalendarMonthPage(
             }
         }
     }
+}
 
 private data class DayData(
     val date: LocalDate,

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarMonthView.kt

@@ -27,13 +27,26 @@ fun CalendarMonthView(
     var currentYear by remember { mutableIntStateOf(viewModel.currentYear) }
     var currentMonth by remember { mutableIntStateOf(viewModel.currentMonth) }
 
-    Column(modifier = modifier.fillMaxSize().statusBarsPadding().padding(horizontal = 16.dp)) {
+    Column(modifier = modifier.fillMaxSize().statusBarsPadding()) {
+        Column(modifier = Modifier.padding(horizontal = 16.dp)) {
             MonthHeader(
                 year = currentYear,
                 month = currentMonth,
                 weekNumber = viewModel.getIsoWeekNumber(viewModel.selectedDate)
             )
             WeekdayHeader(modifier = Modifier.fillMaxWidth())
+            if (viewModel.isCollapsed) {
+                WeekPager(
+                    selectedDate = viewModel.selectedDate,
+                    today = today,
+                    onDateClick = { date -> viewModel.selectDate(date) },
+                    onWeekChanged = { weekMonday ->
+                        currentYear = weekMonday.year
+                        @Suppress("DEPRECATION")
+                        currentMonth = weekMonday.monthNumber
+                    }
+                )
+            } else {
                 CalendarPager(
                     selectedDate = viewModel.selectedDate,
                     today = today,
@@ -42,6 +55,12 @@ fun CalendarMonthView(
                         currentYear = year
                         currentMonth = month
                     },
+                    collapseProgress = viewModel.collapseProgress
+                )
+            }
+        }
+        BottomCard(
+            viewModel = viewModel,
             modifier = Modifier.weight(1f)
         )
     }

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarPager.kt

@@ -20,6 +20,7 @@ fun CalendarPager(
     today: LocalDate,
     onDateClick: (LocalDate) -> Unit,
     onMonthChanged: (year: Int, month: Int) -> Unit,
+    collapseProgress: Float,
     modifier: Modifier = Modifier
 ) {
     val initialYearMonth = remember { today.toYearMonth() }
@@ -61,7 +62,8 @@ fun CalendarPager(
                         }
                     }
                 }
-            }
+            },
+            collapseProgress = collapseProgress
         )
     }
 }

shared/src/commonMain/kotlin/plus/rua/project/ui/WeekPager.kt

@@ -0,0 +1,80 @@
+package plus.rua.project.ui
+
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.pager.HorizontalPager
+import androidx.compose.foundation.pager.PagerDefaults
+import androidx.compose.foundation.pager.rememberPagerState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.snapshotFlow
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.unit.dp
+import kotlinx.coroutines.launch
+import kotlinx.datetime.DatePeriod
+import kotlinx.datetime.LocalDate
+import kotlinx.datetime.minus
+import kotlinx.datetime.plus
+
+private const val START_PAGE = Int.MAX_VALUE / 2
+
+@Composable
+fun WeekPager(
+    selectedDate: LocalDate,
+    today: LocalDate,
+    onDateClick: (LocalDate) -> Unit,
+    onWeekChanged: (LocalDate) -> Unit,
+    modifier: Modifier = Modifier
+) {
+    val initialWeekMonday = remember { selectedDate.toWeekMonday() }
+    val pagerState = rememberPagerState(
+        initialPage = START_PAGE,
+        pageCount = { Int.MAX_VALUE }
+    )
+
+    LaunchedEffect(pagerState) {
+        snapshotFlow { pagerState.settledPage }.collect { page ->
+            val weekMonday = pageToWeekMonday(page, initialWeekMonday)
+            onWeekChanged(weekMonday)
+        }
+    }
+
+    HorizontalPager(
+        state = pagerState,
+        beyondViewportPageCount = 1,
+        flingBehavior = PagerDefaults.flingBehavior(state = pagerState),
+        modifier = modifier
+    ) { page ->
+        val weekMonday = pageToWeekMonday(page, initialWeekMonday)
+        Row(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(vertical = 2.dp)
+        ) {
+            (0 until 7).forEach { dayOffset ->
+                val date = weekMonday.plus(DatePeriod(days = dayOffset))
+                DayCell(
+                    date = date,
+                    isCurrentMonth = true,
+                    isSelected = date == selectedDate,
+                    isToday = date == today,
+                    onClick = { onDateClick(date) },
+                    modifier = Modifier.weight(1f)
+                )
+            }
+        }
+    }
+}
+
+private fun LocalDate.toWeekMonday(): LocalDate {
+    val dayOfWeekOrdinal = dayOfWeek.ordinal // Monday=0 ... Sunday=6
+    return minus(DatePeriod(days = dayOfWeekOrdinal))
+}
+
+private fun pageToWeekMonday(page: Int, initial: LocalDate): LocalDate {
+    val offset = page - START_PAGE
+    return initial.plus(DatePeriod(days = offset * 7))
+}