feat: schedule swiping

app/src/main/java/agzam/vyatsu/ui/schedule/ScheduleScreen.kt

@@ -25,9 +25,15 @@ import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.layout.widthIn
 import androidx.compose.foundation.layout.windowInsetsPadding
 import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.LazyListItemInfo
+import androidx.compose.foundation.lazy.LazyListLayoutInfo
 import androidx.compose.foundation.lazy.LazyRow
 import androidx.compose.foundation.lazy.items
 import androidx.compose.foundation.lazy.itemsIndexed
+import androidx.compose.foundation.lazy.rememberLazyListState
+import androidx.compose.foundation.pager.HorizontalPager
+import androidx.compose.foundation.pager.PagerState
+import androidx.compose.foundation.pager.rememberPagerState
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.foundation.text.selection.SelectionContainer
 import androidx.compose.material.icons.Icons
@@ -48,20 +54,27 @@ import androidx.compose.material3.Text
 import androidx.compose.material3.TextButton
 import androidx.compose.material3.TopAppBar
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
+import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.compositeOver
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.unit.dp
+import kotlinx.coroutines.flow.collectLatest
 import java.time.DayOfWeek
 import java.time.LocalDate
 import java.time.format.DateTimeFormatter
+import kotlin.math.absoluteValue
+import kotlin.math.max
+import kotlin.math.min
 
 
 val hPadding = 16.dp
@@ -128,6 +141,32 @@ fun ScheduleScreen(viewModel: ScheduleViewModel, onSwitchGroup: () -> Unit) {
                     if (day == null) {
                         Text("Занятий нет", style = MaterialTheme.typography.bodyLarge)
                     } else {
+
+                        val schedule = state.schedule!!
+                        val weekDays = state.weekStart
+                            ?.let { ws -> schedule.periods.firstOrNull { it.weekStart == ws } }
+                            ?.let { schedule.daysOf(it) }
+                            .orEmpty()
+
+                        val selectedDayIndex = weekDays.indexOfFirst { it.date == state.dayDate }.coerceAtLeast(0)
+                        val pagerState = rememberPagerState(
+                            initialPage = selectedDayIndex,
+                            pageCount = { weekDays.size }
+                        )
+                        LaunchedEffect(state.dayDate) {
+                            val targetPage = weekDays.indexOfFirst { it.date == state.dayDate }
+                            if (targetPage != -1 && targetPage != pagerState.currentPage) {
+                                pagerState.scrollToPage(targetPage) // Мгновенное переключение без анимации
+                            }
+                        }
+                        LaunchedEffect(pagerState) {
+                            snapshotFlow { pagerState.currentPage }.collect { page ->
+                                if (pagerState.isScrollInProgress && page in weekDays.indices) {
+                                    viewModel.selectDay(weekDays[page].date)
+                                }
+                            }
+                        }
+
                         val isTodayDay = day.date == state.todayDate
                         val dayLabel = if (isTodayDay) "Сегодня " else ""
 
@@ -153,20 +192,31 @@ fun ScheduleScreen(viewModel: ScheduleViewModel, onSwitchGroup: () -> Unit) {
                             days = weekDays,
                             selectedDate = state.dayDate,
                             todayDate = state.todayDate,
-                            onSelect = viewModel::selectDay
+                            onSelect = viewModel::selectDay,
+                            pagerState = pagerState
                         )
 
                         HorizontalDivider(Modifier.padding(top=0.dp, start = hPadding, end = hPadding))
-                        if (day.intervals.all { it.lessons.isEmpty() }) {
+
-                            Text("Занятий нет", style = MaterialTheme.typography.bodyLarge)
+                        HorizontalPager(state = pagerState, modifier = Modifier.weight(1f)) { page ->
-                        } else {
+                            val day = weekDays.getOrNull(page)
-                            LazyColumn(
+
-                                modifier = Modifier.weight(1f),
+                            if (day == null || day.intervals.all { it.lessons.isEmpty() }) {
-                                verticalArrangement = Arrangement.spacedBy(8.dp),
+                                Box(
-                                contentPadding = PaddingValues(vertical = 8.dp)
+                                    modifier = Modifier.fillMaxSize(),
-                            ) {
+                                    contentAlignment = Alignment.Center
-                                itemsIndexed(day.intervals) { slotIndex, slot ->
+                                ) {
-                                    LessonSlot(slotIndex = slotIndex, slot = slot)
+                                    Text("Занятий нет", style = MaterialTheme.typography.bodyLarge)
+                                }
+                            } else {
+                                LazyColumn(
+                                    modifier = Modifier.fillMaxSize(),
+                                    verticalArrangement = Arrangement.spacedBy(8.dp),
+                                    contentPadding = PaddingValues(vertical = 8.dp)
+                                ) {
+                                    itemsIndexed(day.intervals) { slotIndex, slot ->
+                                        LessonSlot(slotIndex = slotIndex, slot = slot)
+                                    }
                                 }
                             }
                         }
@@ -242,14 +292,66 @@ private fun WeekSelector(
     }
 }
 
+private fun getVisiblePercentage(item: LazyListItemInfo, layoutInfo: LazyListLayoutInfo): Float {
+    val viewportStart = layoutInfo.viewportStartOffset
+    val viewportEnd = layoutInfo.viewportEndOffset
+
+    val itemStart = item.offset
+    val itemEnd = item.offset + item.size
+
+    val visibleStart = max(itemStart, viewportStart)
+    val visibleEnd = min(itemEnd, viewportEnd)
+    val visibleSize = visibleEnd - visibleStart
+
+    return if (visibleSize <= 0) 0f else visibleSize.toFloat() / item.size
+}
+
 @Composable
 private fun DayChips(
     days: List<Day>,
     selectedDate: LocalDate?,
     todayDate: LocalDate?,
+    pagerState: PagerState,
     onSelect: (LocalDate) -> Unit
 ) {
-    LazyRow(horizontalArrangement = Arrangement.spacedBy(6.dp), contentPadding = PaddingValues(horizontal = hPadding, vertical = 2.dp),) {
+    val listState = rememberLazyListState()
+
+    val density = LocalDensity.current
+
+    val paddingPx = with(density) { hPadding.toPx() }
+
+
+    LaunchedEffect(pagerState, days) {
+        snapshotFlow {
+            pagerState.settledPage
+        }.collectLatest { targetPage ->
+
+            if (targetPage in days.indices) {
+                val layoutInfo = listState.layoutInfo
+                var visibleItems = layoutInfo.visibleItemsInfo
+                var targetItem = visibleItems.firstOrNull { it.index == targetPage }
+                if (targetItem == null) {
+                    listState.scrollToItem(index = targetPage)
+                    val updatedLayout = listState.layoutInfo
+                    visibleItems = updatedLayout.visibleItemsInfo
+                    targetItem = visibleItems.firstOrNull { it.index == targetPage }
+                }
+                if (targetItem != null) {
+                    val visiblePercentage = getVisiblePercentage(targetItem, layoutInfo)
+                    val minVisibleThreshold = 0.75f
+                    if (visiblePercentage < minVisibleThreshold) {
+                        val viewPortWidth = layoutInfo.viewportEndOffset - layoutInfo.viewportStartOffset
+                        val halfViewport = viewPortWidth / 2f
+                        val centerOffset = (halfViewport - (targetItem.size / 2f) - paddingPx).toInt()
+                        listState.animateScrollToItem(index = targetPage, scrollOffset = -centerOffset)
+                    }
+                }
+            }
+        }
+    }
+
+
+    LazyRow(state = listState, horizontalArrangement = Arrangement.spacedBy(6.dp), contentPadding = PaddingValues(horizontal = hPadding, vertical = 2.dp),) {
         items(days, key = { it.date.toEpochDay() }) { day ->
             val selected = selectedDate == day.date
             val isTodayChip = todayDate == day.date