import 'package:decimal/decimal.dart';
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../../core/utils/compact_number.dart';
import '../../core/utils/ru_date.dart';
import '../../core/widgets/async_value_view.dart';
import '../../core/widgets/money_text.dart';
import '../../core/widgets/section_card.dart';
import 'data/income_api.dart';
import 'entry_row.dart';
import 'labels.dart';
import 'providers.dart';

const _weekdays = ['Пн', 'Вт', 'Ср', 'Чт', 'Пт', 'Сб', 'Вс'];

/// Kinds in the order their glyphs are laid out inside a day cell.
const _kindOrder = ['dividend', 'coupon', 'amortization', 'repayment'];

/// When several payments of one kind share a day, the cell shows the least certain basis:
/// a guess must not be hidden behind a fact that happens to fall on the same day.
const _basisOrder = ['history', 'schedule', 'announced', 'paid'];

/// The month grid: every dividend, coupon, amortisation and redemption on the day it falls,
/// paid ones beside the expected ones. A day opens its payments beside or below the grid.
///
/// The screen itself does not scroll: the grid takes the height it is given, and only the
/// list of payments — the one part that can be any length — scrolls inside its own panel.
class IncomeMonthView extends ConsumerStatefulWidget {
  const IncomeMonthView({super.key});

  @override
  ConsumerState<IncomeMonthView> createState() => _IncomeMonthViewState();
}

class _IncomeMonthViewState extends ConsumerState<IncomeMonthView> {
  int? _selectedDay;

  void _setMonth(DateTime month) {
    ref.read(calendarMonthProvider.notifier).state = month;
    setState(() => _selectedDay = null);
  }

  @override
  Widget build(BuildContext context) {
    final month = ref.watch(calendarMonthProvider);
    final data = ref.watch(incomeMonthProvider(month));
    final now = DateTime.now();
    final isCurrent = month.year == now.year && month.month == now.month;
    const dense = VisualDensity.compact;

    return Padding(
      padding: const EdgeInsets.fromLTRB(16, 0, 16, 8),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Row(
            children: [
              IconButton(
                visualDensity: dense,
                tooltip: 'Предыдущий месяц',
                icon: const Icon(Icons.chevron_left),
                onPressed: () =>
                    _setMonth(DateTime(month.year, month.month - 1)),
              ),
              Expanded(
                child: Text(
                  ruMonthYear(month),
                  textAlign: TextAlign.center,
                  style: Theme.of(context).textTheme.titleMedium,
                ),
              ),
              IconButton(
                visualDensity: dense,
                tooltip: 'Следующий месяц',
                icon: const Icon(Icons.chevron_right),
                onPressed: () =>
                    _setMonth(DateTime(month.year, month.month + 1)),
              ),
              TextButton(
                style: TextButton.styleFrom(visualDensity: dense),
                onPressed: isCurrent
                    ? null
                    : () => _setMonth(DateTime(now.year, now.month)),
                child: const Text('Сегодня'),
              ),
            ],
          ),
          Expanded(
            child: AsyncValueView(
              value: data,
              onRetry: () => ref.invalidate(incomeMonthProvider(month)),
              data: (cached) => _MonthBody(
                month: month,
                entries: cached.data.entries,
                selectedDay: _selectedDay,
                onSelect: (day) => setState(
                  () => _selectedDay = day == _selectedDay ? null : day,
                ),
                onRefresh: () async =>
                    ref.invalidate(incomeMonthProvider(month)),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

/// Width from which the payments sit beside the grid instead of under it.
const _wideFrom = 840.0;

/// Room the parts around the grid take, for sizing its rows from the height that is left.
const _weekdayRow = 24.0;
const _legendRow = 32.0;

/// On a narrow screen the legend wraps onto several lines.
const _legendRowNarrow = 64.0;
const _detailsMin = 150.0;

class _MonthBody extends StatelessWidget {
  const _MonthBody({
    required this.month,
    required this.entries,
    required this.selectedDay,
    required this.onSelect,
    required this.onRefresh,
  });

  final DateTime month;
  final List<IncomeEntry> entries;
  final int? selectedDay;
  final ValueChanged<int> onSelect;
  final Future<void> Function() onRefresh;

  @override
  Widget build(BuildContext context) {
    final inMonth = [
      for (final e in entries)
        if (e.expectedDate != null &&
            e.expectedDate!.year == month.year &&
            e.expectedDate!.month == month.month)
          e,
    ];
    final byDay = <int, List<IncomeEntry>>{};
    for (final e in inMonth) {
      byDay.putIfAbsent(e.expectedDate!.day, () => []).add(e);
    }
    final shown = selectedDay == null
        ? inMonth
        : byDay[selectedDay] ?? const <IncomeEntry>[];

    final lead = DateTime(month.year, month.month).weekday - 1;
    final days = DateTime(month.year, month.month + 1, 0).day;
    final weeks = ((lead + days) / 7).ceil();

    Widget grid(double cellHeight) => _Grid(
      month: month,
      byDay: byDay,
      selectedDay: selectedDay,
      onSelect: onSelect,
      lead: lead,
      days: days,
      weeks: weeks,
      cellHeight: cellHeight,
    );
    final legend = _Legend(entries: inMonth);
    final details = _Details(
      title: selectedDay == null
          ? 'Выплаты за месяц'
          : ruDate(DateTime(month.year, month.month, selectedDay!)),
      entries: shown,
      onRefresh: onRefresh,
    );

    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        _Summary(entries: inMonth),
        const SizedBox(height: 8),
        Expanded(
          child: LayoutBuilder(
            builder: (context, c) {
              if (c.maxWidth >= _wideFrom) {
                // grid on the left fills the height; payments on the right
                final cell = ((c.maxHeight - _weekdayRow - _legendRow) / weeks)
                    .clamp(48.0, 104.0);
                return Row(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Expanded(
                      flex: 3,
                      child: Column(
                        children: [
                          grid(cell),
                          const SizedBox(height: 8),
                          legend,
                        ],
                      ),
                    ),
                    const SizedBox(width: 16),
                    Expanded(flex: 2, child: details),
                  ],
                );
              }
              // narrow: rows shrink to leave the payments room underneath
              final cell =
                  ((c.maxHeight -
                              _weekdayRow -
                              _legendRowNarrow -
                              _detailsMin) /
                          weeks)
                      .clamp(40.0, 60.0);
              return Column(
                children: [
                  grid(cell),
                  const SizedBox(height: 8),
                  legend,
                  const SizedBox(height: 8),
                  Expanded(child: details),
                ],
              );
            },
          ),
        ),
      ],
    );
  }
}

/// The payments of the chosen day (or of the month), scrolling inside their own panel.
class _Details extends StatelessWidget {
  const _Details({
    required this.title,
    required this.entries,
    required this.onRefresh,
  });

  final String title;
  final List<IncomeEntry> entries;
  final Future<void> Function() onRefresh;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return RefreshIndicator(
      onRefresh: onRefresh,
      child: ListView(
        padding: EdgeInsets.zero,
        children: [
          SectionCard(
            title: title,
            child: entries.isEmpty
                ? Padding(
                    padding: const EdgeInsets.symmetric(vertical: 8),
                    child: Text(
                      'Выплат нет.',
                      style: theme.textTheme.bodyMedium?.copyWith(
                        color: theme.hintColor,
                      ),
                    ),
                  )
                : Column(
                    children: [
                      for (final e in entries) IncomeEntryRow(entry: e),
                    ],
                  ),
          ),
        ],
      ),
    );
  }
}

class _Sum {
  const _Sum(this.total, this.unconverted);

  final Decimal total;

  /// Payments with no rouble figure (no FX rate for the day): left out of [total], not zeroed.
  final int unconverted;
}

_Sum _sum(Iterable<IncomeEntry> entries) {
  var total = Decimal.zero;
  var unconverted = 0;
  for (final e in entries) {
    final v = Decimal.tryParse(e.amountRub ?? '');
    if (v == null) {
      unconverted++;
    } else {
      total += v;
    }
  }
  return _Sum(total, unconverted);
}

/// One line: what came in, what is still expected. What qualifies the numbers — a share that
/// is only an extrapolation, payments with no rouble figure — sits behind the info icon.
class _Summary extends StatelessWidget {
  const _Summary({required this.entries});

  final List<IncomeEntry> entries;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final paid = _sum(entries.where((e) => e.basis == 'paid'));
    final expected = _sum(entries.where((e) => e.basis != 'paid'));
    final guess = _sum(entries.where((e) => e.basis == 'history')).total;
    final unconverted = paid.unconverted + expected.unconverted;

    Widget stat(String label, Color color, Decimal value) => Row(
      mainAxisSize: MainAxisSize.min,
      children: [
        Text(
          '$label ',
          style: theme.textTheme.bodySmall?.copyWith(color: theme.hintColor),
        ),
        MoneyText(
          value.toString(),
          currency: 'RUB',
          style: theme.textTheme.titleSmall?.copyWith(color: color),
        ),
      ],
    );

    final notes = [
      if (guess > Decimal.zero)
        'Из ожидаемого ${MoneyText.format(guess.toString(), 'RUB')} — '
            'экстраполяция по истории: этих выплат может не быть.',
      if (unconverted > 0)
        'У $unconverted выплат нет курса на дату — в суммы они не вошли.',
    ];

    return Wrap(
      spacing: 20,
      runSpacing: 2,
      crossAxisAlignment: WrapCrossAlignment.center,
      children: [
        stat('Получено', basisColor('paid'), paid.total),
        stat('Ожидается', basisColor('schedule'), expected.total),
        if (notes.isNotEmpty)
          Tooltip(
            message: notes.join('\n'),
            triggerMode: TooltipTriggerMode.tap,
            showDuration: const Duration(seconds: 6),
            child: Icon(
              Icons.info_outline,
              size: 18,
              color: basisColor('history'),
            ),
          ),
      ],
    );
  }
}

class _Grid extends StatelessWidget {
  const _Grid({
    required this.month,
    required this.byDay,
    required this.selectedDay,
    required this.onSelect,
    required this.lead,
    required this.days,
    required this.weeks,
    required this.cellHeight,
  });

  final DateTime month;
  final Map<int, List<IncomeEntry>> byDay;
  final int? selectedDay;
  final ValueChanged<int> onSelect;
  final int lead;
  final int days;
  final int weeks;
  final double cellHeight;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final now = DateTime.now();

    return Column(
      children: [
        SizedBox(
          height: _weekdayRow,
          child: Row(
            children: [
              for (final w in _weekdays)
                Expanded(
                  child: Center(
                    child: Text(
                      w,
                      style: theme.textTheme.labelMedium?.copyWith(
                        color: theme.hintColor,
                      ),
                    ),
                  ),
                ),
            ],
          ),
        ),
        for (var w = 0; w < weeks; w++)
          Row(
            children: [
              for (var c = 0; c < 7; c++)
                Expanded(
                  child: Builder(
                    builder: (_) {
                      final day = w * 7 + c - lead + 1;
                      if (day < 1 || day > days) {
                        return SizedBox(height: cellHeight);
                      }
                      return _DayCell(
                        day: day,
                        height: cellHeight,
                        entries: byDay[day] ?? const [],
                        isToday:
                            month.year == now.year &&
                            month.month == now.month &&
                            day == now.day,
                        selected: day == selectedDay,
                        onTap: () => onSelect(day),
                      );
                    },
                  ),
                ),
            ],
          ),
      ],
    );
  }
}

class _DayCell extends StatelessWidget {
  const _DayCell({
    required this.day,
    required this.height,
    required this.entries,
    required this.isToday,
    required this.selected,
    required this.onTap,
  });

  final int day;
  final double height;
  final List<IncomeEntry> entries;
  final bool isToday;
  final bool selected;
  final VoidCallback onTap;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final primary = theme.colorScheme.primary;

    final kinds = [
      for (final k in _kindOrder)
        if (entries.any((e) => e.kind == k)) k,
      // a kind the server invents later still gets a glyph rather than vanishing
      for (final k in {for (final e in entries) e.kind})
        if (!_kindOrder.contains(k)) k,
    ];
    final sum = _sum(entries);
    final hasAmount = entries.isNotEmpty && sum.unconverted < entries.length;

    return LayoutBuilder(
      builder: (context, c) {
        final narrow = c.maxWidth < 72;
        // a wide but short cell keeps the day and the glyphs on one line
        final oneLine = !narrow && height < 64;
        final showAmount = !narrow && height >= 64 && hasAmount;
        final iconSize = narrow || height < 64 ? 12.0 : 15.0;

        final dayText = Text(
          '$day',
          style: theme.textTheme.bodySmall?.copyWith(
            fontWeight: isToday ? FontWeight.w700 : null,
            color: isToday ? primary : null,
          ),
        );
        final glyphs = Wrap(
          spacing: 2,
          runSpacing: 2,
          alignment: oneLine ? WrapAlignment.end : WrapAlignment.start,
          children: [
            for (final k in kinds)
              Icon(
                incomeKindIcon(k),
                size: iconSize,
                color: basisColor(
                  _leastCertain(entries.where((e) => e.kind == k)),
                ),
              ),
          ],
        );

        return Padding(
          padding: const EdgeInsets.all(1.5),
          child: Material(
            color: selected
                ? primary.withValues(alpha: 0.16)
                : entries.isEmpty
                ? Colors.transparent
                : theme.colorScheme.surfaceContainerHighest.withValues(
                    alpha: 0.5,
                  ),
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(8),
              side: isToday
                  ? BorderSide(color: primary)
                  : selected
                  ? BorderSide(color: primary.withValues(alpha: 0.5))
                  : BorderSide(
                      color: theme.dividerColor.withValues(alpha: 0.4),
                    ),
            ),
            child: InkWell(
              borderRadius: BorderRadius.circular(8),
              onTap: onTap,
              child: SizedBox(
                height: height - 3,
                child: Padding(
                  padding: EdgeInsets.all(narrow ? 4 : 6),
                  child: oneLine
                      ? Row(
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: [dayText, const Spacer(), glyphs],
                        )
                      : Column(
                          crossAxisAlignment: CrossAxisAlignment.start,
                          mainAxisAlignment: MainAxisAlignment.spaceBetween,
                          children: [
                            dayText,
                            glyphs,
                            if (showAmount)
                              Text(
                                '${sum.unconverted > 0 ? '≥ ' : ''}${compactNumber(sum.total.toDouble())}',
                                maxLines: 1,
                                overflow: TextOverflow.ellipsis,
                                style: theme.textTheme.labelSmall,
                              ),
                          ],
                        ),
                ),
              ),
            ),
          ),
        );
      },
    );
  }
}

String _leastCertain(Iterable<IncomeEntry> entries) {
  final bases = entries.map((e) => e.basis).toSet();
  for (final b in _basisOrder) {
    if (bases.contains(b)) return b;
  }
  return bases.first;
}

/// What the glyphs and colours mean, and only for what is on this month's grid.
class _Legend extends StatelessWidget {
  const _Legend({required this.entries});

  final List<IncomeEntry> entries;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final bases = {for (final e in entries) e.basis};
    return Wrap(
      spacing: 16,
      runSpacing: 4,
      crossAxisAlignment: WrapCrossAlignment.center,
      children: [
        for (final k in _kindOrder)
          Row(
            mainAxisSize: MainAxisSize.min,
            children: [
              Icon(incomeKindIcon(k), size: 15, color: theme.hintColor),
              const SizedBox(width: 4),
              Text(incomeKindLabel(k), style: theme.textTheme.bodySmall),
            ],
          ),
        for (final b in _basisOrder.reversed)
          if (bases.contains(b)) BasisChip(basis: b),
      ],
    );
  }
}