package plus.rua.project.ui

import androidx.compose.animation.AnimatedContent
import androidx.compose.animation.core.tween
import androidx.compose.animation.slideInVertically
import androidx.compose.animation.slideOutVertically
import androidx.compose.animation.togetherWith
import androidx.compose.foundation.Canvas
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
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.CircleShape
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.drawText
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.rememberTextMeasurer
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.platform.LocalDensity
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import kotlinx.datetime.DatePeriod
import kotlinx.datetime.LocalDate
import kotlinx.datetime.minus
import kotlinx.datetime.number
import kotlinx.datetime.plus
import plus.rua.project.composeTraceBeginSection
import plus.rua.project.composeTraceEndSection

private val WEEKDAY_LABELS = listOf("一", "二", "三", "四", "五", "六", "日")

/**
 * 年视图 4×3 月历网格。
 *
 * @param year 显示的年份
 * @param selectedMonth 当前选中月份（1-12）
 * @param today 今天的日期
 * @param onMonthClick 月份点击回调
 * @param modifier 外部布局修饰符
 */
@Composable
fun YearGridView(
    year: Int,
    selectedMonth: Int,
    today: LocalDate,
    onMonthClick: (Int) -> Unit,
    modifier: Modifier = Modifier
) {
    composeTraceBeginSection("YearGridView:$year")
    Column(
        modifier = modifier.fillMaxSize(),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        // 4×3 月历网格
        Column(
            modifier = Modifier
                .fillMaxWidth()
                .weight(1f)
                .padding(horizontal = 4.dp),
            verticalArrangement = Arrangement.spacedBy(12.dp)
        ) {
            (0 until 4).forEach { row ->
                Row(
                    modifier = Modifier.fillMaxWidth(),
                    horizontalArrangement = Arrangement.spacedBy(8.dp)
                ) {
                    (0 until 3).forEach { col ->
                        val month = row * 3 + col + 1
                        MiniMonth(
                            year = year,
                            month = month,
                            isSelected = month == selectedMonth,
                            today = today,
                            onClick = { onMonthClick(month) },
                            modifier = Modifier.weight(1f)
                        )
                    }
                }
            }
        }
    }
    composeTraceEndSection()
}

/**
 * 精简版月历：月份标题 + 星期行 + 日期数字网格。
 */
@Composable
private fun MiniMonth(
    year: Int,
    month: Int,
    isSelected: Boolean,
    today: LocalDate,
    onClick: () -> Unit,
    modifier: Modifier = Modifier
) {
    val days = remember(year, month) { generateMiniMonthDays(year, month) }
    val titleColor = if (isSelected) {
        MaterialTheme.colorScheme.primary
    } else {
        MaterialTheme.colorScheme.onSurface
    }
    val weekdayColor = MaterialTheme.colorScheme.onSurface.copy(alpha = 0.4f)
    val dayColor = MaterialTheme.colorScheme.onSurface.copy(alpha = 0.6f)
    val otherMonthColor = MaterialTheme.colorScheme.onSurface.copy(alpha = 0.2f)
    val todayBgColor = MaterialTheme.colorScheme.primaryContainer
    val todayTextColor = MaterialTheme.colorScheme.onPrimaryContainer

    val textMeasurer = rememberTextMeasurer()
    val dayTextStyle = remember {
        TextStyle(fontSize = 8.sp, lineHeight = 12.sp)
    }

    Column(
        modifier = modifier
            .padding(2.dp)
            .clickable(onClick = onClick)
            .padding(vertical = 2.dp),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        // 月份标题
        Text(
            text = "${month}月",
            color = titleColor,
            fontSize = 10.sp,
            fontWeight = if (isSelected) FontWeight.Bold else FontWeight.Normal,
            textAlign = TextAlign.Center
        )
        // 星期行
        Row(
            modifier = Modifier.fillMaxWidth(),
            horizontalArrangement = Arrangement.SpaceEvenly
        ) {
            WEEKDAY_LABELS.forEach { label ->
                Text(
                    text = label,
                    color = weekdayColor,
                    fontSize = 8.sp,
                    textAlign = TextAlign.Center,
                    modifier = Modifier.weight(1f)
                )
            }
        }
        // 日期网格 — Canvas 绘制
        val density = LocalDensity.current
        val dayRowCount = days.size / 7
        val canvasHeight = with(density) { (dayRowCount * (12.sp.toPx() + 4.dp.toPx())).toDp() }
        Canvas(modifier = Modifier.fillMaxWidth().height(canvasHeight)) {
            val cellWidth = size.width / 7f
            val rowHeightPx = size.height / dayRowCount

            days.forEachIndexed { index, dayData ->
                val row = index / 7
                val col = index % 7
                val centerX = col * cellWidth + cellWidth / 2f
                val centerY = row * rowHeightPx + rowHeightPx / 2f

                val isToday = dayData.date == today && dayData.isCurrentMonth
                val text = if (dayData.isCurrentMonth) dayData.date.day.toString() else ""
                val textColor: Color = when {
                    !dayData.isCurrentMonth -> otherMonthColor
                    isToday -> todayTextColor
                    else -> dayColor
                }

                if (isToday) {
                    val radius = cellWidth.coerceAtMost(rowHeightPx) / 2f * 0.8f
                    drawCircle(
                        color = todayBgColor,
                        radius = radius,
                        center = Offset(centerX, centerY)
                    )
                }

                if (text.isNotEmpty()) {
                    val measured = textMeasurer.measure(
                        text = text,
                        style = dayTextStyle.copy(color = textColor)
                    )
                    drawText(
                        textLayoutResult = measured,
                        topLeft = Offset(
                            x = centerX - measured.size.width / 2f,
                            y = centerY - measured.size.height / 2f
                        )
                    )
                }
            }
        }
    }
}

private data class MiniDayData(
    val date: LocalDate,
    val isCurrentMonth: Boolean
)

@Suppress("DEPRECATION") // monthNumber 无替代 API
private fun generateMiniMonthDays(year: Int, month: Int): List<MiniDayData> {
    composeTraceBeginSection("generateMiniMonthDays:$year-$month")
    val firstOfMonth = LocalDate(year, month, 1)
    val offset = firstOfMonth.dayOfWeek.ordinal
    val startDate = firstOfMonth.minus(DatePeriod(days = offset))
    val nextMonth = if (month == 12) LocalDate(year + 1, 1, 1) else LocalDate(year, month + 1, 1)
    val daysInMonth = nextMonth.minus(DatePeriod(days = 1)).day
    val rows = ((offset + daysInMonth - 1) / 7) + 1
    val totalDays = rows * 7

    val result = (0 until totalDays).map { i ->
        val date = startDate.plus(DatePeriod(days = i))
        MiniDayData(
            date = date,
            isCurrentMonth = date.month.number == month && date.year == year
        )
    }
    composeTraceEndSection()
    return result
}

/**
 * 年视图标题栏，显示年份文字和左右导航箭头。
 *
 * 年份切换时文字有垂直滑动过渡动画，方向由新旧年份大小决定。
 *
 * @param year 当前年份
 * @param onYearChange 年份切换回调
 * @param modifier 外部布局修饰符
 */
@Composable
fun YearHeader(
    year: Int,
    onYearChange: (Int) -> Unit,
    modifier: Modifier = Modifier
) {
    Row(
        modifier = modifier
            .fillMaxWidth()
            .padding(vertical = 8.dp),
        verticalAlignment = Alignment.CenterVertically
    ) {
        Text(
            text = "‹",
            fontSize = 24.sp,
            fontWeight = FontWeight.Bold,
            color = MaterialTheme.colorScheme.primary,
            modifier = Modifier
                .clip(CircleShape)
                .clickable { onYearChange(year - 1) }
                .padding(horizontal = 16.dp, vertical = 8.dp)
        )
        Box(modifier = Modifier.weight(1f), contentAlignment = Alignment.Center) {
            AnimatedContent(
                targetState = year,
                transitionSpec = {
                    if (targetState > initialState) {
                        slideInVertically(tween(250)) { -it } togetherWith
                                slideOutVertically(tween(250)) { it }
                    } else {
                        slideInVertically(tween(250)) { it } togetherWith
                                slideOutVertically(tween(250)) { -it }
                    }
                }
            ) { y ->
                Text(
                    text = "${y}年",
                    style = MaterialTheme.typography.titleLarge,
                    fontWeight = FontWeight.Bold
                )
            }
        }
        Text(
            text = "›",
            fontSize = 24.sp,
            fontWeight = FontWeight.Bold,
            color = MaterialTheme.colorScheme.primary,
            modifier = Modifier
                .clip(CircleShape)
                .clickable { onYearChange(year + 1) }
                .padding(horizontal = 16.dp, vertical = 8.dp)
        )
    }
}