package plus.rua.project.ui

import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.offset
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.statusBarsPadding
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableIntStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberCoroutineScope
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.layout.onSizeChanged
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.unit.dp
import kotlinx.datetime.LocalDate
import kotlinx.datetime.TimeZone
import kotlinx.datetime.todayIn
import kotlin.time.Clock
import plus.rua.project.CalendarViewModel

@Composable
fun CalendarMonthView(
    modifier: Modifier = Modifier
) {
    val coroutineScope = rememberCoroutineScope()
    val viewModel = remember { CalendarViewModel(coroutineScope) }
    val today = remember { Clock.System.todayIn(TimeZone.currentSystemDefault()) }
    var currentYear by remember { mutableIntStateOf(viewModel.currentYear) }
    var currentMonth by remember { mutableIntStateOf(viewModel.currentMonth) }
    val density = LocalDensity.current

    var calendarHeightPx by remember { mutableIntStateOf(0) }
    var screenHeightPx by remember { mutableIntStateOf(0) }
    var expandedCalendarHeightPx by remember { mutableIntStateOf(0) }

    val collapseOffsetPx = if (viewModel.isCollapsed) {
        0
    } else {
        -(viewModel.collapseProgress * expandedCalendarHeightPx * 5f / 6f).toInt()
    }
    val cardTopPx = if (viewModel.isCollapsed) {
        calendarHeightPx
    } else {
        expandedCalendarHeightPx + collapseOffsetPx
    }
    val cardHeightPx = screenHeightPx - cardTopPx

    Box(
        modifier = modifier
            .fillMaxSize()
            .statusBarsPadding()
            .onSizeChanged { size ->
                screenHeightPx = size.height
            }
    ) {
        Column(modifier = Modifier.padding(horizontal = 16.dp).onSizeChanged { size ->
            calendarHeightPx = size.height
            if (!viewModel.isCollapsed && viewModel.collapseProgress < 0.01f) {
                expandedCalendarHeightPx = size.height
            }
        }) {
            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,
                    onDateClick = { date -> viewModel.selectDate(date) },
                    onMonthChanged = { year, month ->
                        currentYear = year
                        currentMonth = month
                    },
                    collapseProgress = viewModel.collapseProgress
                )
            }
        }
        if (cardHeightPx > 0) {
            BottomCard(
                viewModel = viewModel,
                modifier = Modifier
                    .fillMaxWidth()
                    .height(with(density) { cardHeightPx.toDp() })
                    .align(Alignment.BottomCenter)
            )
        }
    }
}