import 'dart:math' as math;

import 'package:flutter/material.dart';

import '../../domain/schedule_engine.dart';
import '../../domain/app_settings.dart';
import '../../app/app_theme.dart';
import 'course_details.dart';

class WeekGrid extends StatelessWidget {
  const WeekGrid({
    super.key,
    required this.events,
    required this.monday,
    required this.today,
    required this.settings,
  });
  final List<CourseOccurrence> events;
  final DateTime monday, today;
  final AppSettings settings;
  static const _nameStyle = TextStyle(
    fontSize: 10.5,
    fontWeight: FontWeight.w700,
    height: 1.25,
  );
  static const _metadataStyle = TextStyle(fontSize: 9.5, height: 1.22);

  List<CourseOccurrence> _group(CourseOccurrence event) {
    final values = events
        .where((e) => e.course.weekday == event.course.weekday)
        .toList();
    final connected = <CourseOccurrence>{event};
    var grew = true;
    while (grew) {
      grew = false;
      for (final other in values) {
        if (!connected.contains(other) &&
            connected.any((known) => ScheduleEngine.overlaps(known, other))) {
          connected.add(other);
          grew = true;
        }
      }
    }
    return values.where(connected.contains).toList();
  }

  @override
  Widget build(BuildContext context) => LayoutBuilder(
    builder: (context, constraints) {
      final scaler = MediaQuery.textScalerOf(context);
      final scale = scaler.scale(10) / 10;
      const gutter = 34.0, gap = 16.0;
      final width = (constraints.maxWidth - gutter) / 7;
      final header = 56.0 * scale.clamp(1, 2.5);
      final groups = {for (final e in events) e: _group(e)};
      final defaultStyle = DefaultTextStyle.of(context).style;
      double measure(
        String value,
        TextStyle style,
        double available, {
        int? lines,
      }) {
        final painter = TextPainter(
          text: TextSpan(text: value, style: defaultStyle.merge(style)),
          textDirection: Directionality.of(context),
          textScaler: scaler,
          maxLines: lines,
          ellipsis: lines == null ? null : '…',
        )..layout(maxWidth: available);
        final result = painter.height;
        painter.dispose();
        return result;
      }

      // A single shared lesson height keeps equal-duration cards identical in size.
      // Increase that height for full metadata, never stretch one card independently.
      var rowHeight = 54.0 * settings.courseHeightScale * scale.clamp(1, 2.5);
      for (final e in events) {
        final group = groups[e]!;
        if (group.first != e) continue;
        final available = math.max(1.0, width - 12);
        var entryHeight = 0.0;
        for (final value in group) {
          final required =
              measure(value.course.name, _nameStyle, available, lines: 2) +
              measure(value.course.teacher, _metadataStyle, available) +
              measure(value.course.room, _metadataStyle, available) +
              21;
          final periodHeight = group.length > 1
              ? measure(
                      '${value.course.startPeriod}–${value.course.endPeriod}节',
                      _metadataStyle,
                      available,
                    ) +
                    3
              : 0.0;
          entryHeight = math.max(entryHeight, required + periodHeight);
        }
        final first = group.map((v) => v.course.startPeriod).reduce(math.min);
        final last = group.map((v) => v.course.endPeriod).reduce(math.max);
        final warning = group.length > 1
            ? measure('冲突列表', _metadataStyle, width - 12) + 8
            : 0.0;
        rowHeight = math.max(
          rowHeight,
          (entryHeight * group.length + warning + 8) / (last - first + 1),
        );
      }
      rowHeight = rowHeight.ceilToDouble();
      double top(int period) =>
          (period - 1) * rowHeight +
          (period > 4 ? gap : 0) +
          (period > 8 ? gap : 0);
      final height = 11 * rowHeight + 2 * gap;
      return Row(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          SizedBox(
            width: gutter,
            height: header + height,
            child: Stack(
              children: [
                for (final slot in lessonSlots)
                  Positioned(
                    top: header + top(slot.period),
                    left: 0,
                    right: 3,
                    height: rowHeight,
                    child: Column(
                      mainAxisAlignment: MainAxisAlignment.center,
                      children: [
                        Text(
                          '${slot.period}',
                          style: const TextStyle(
                            fontSize: 11,
                            fontWeight: FontWeight.w700,
                          ),
                        ),
                        const SizedBox(height: 3),
                        FittedBox(
                          child: Text(
                            minuteLabel(slot.startMinute),
                            style: TextStyle(
                              fontSize: 8,
                              color: ink.withValues(alpha: 0.55),
                            ),
                          ),
                        ),
                        FittedBox(
                          child: Text(
                            minuteLabel(slot.endMinute),
                            style: TextStyle(
                              fontSize: 8,
                              color: ink.withValues(alpha: 0.4),
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
              ],
            ),
          ),
          Expanded(
            child: Column(
              children: [
                SizedBox(
                  height: header,
                  child: Row(
                    children: List.generate(7, (i) {
                      final date = monday.add(Duration(days: i));
                      final active =
                          date.year == today.year &&
                          date.month == today.month &&
                          date.day == today.day;
                      return SizedBox(
                        width: width,
                        child: Column(
                          mainAxisAlignment: MainAxisAlignment.center,
                          children: [
                            Text(
                              const [
                                '周一',
                                '周二',
                                '周三',
                                '周四',
                                '周五',
                                '周六',
                                '周日',
                              ][i],
                              textAlign: TextAlign.center,
                              style: TextStyle(
                                fontSize: 10,
                                color: active
                                    ? river
                                    : ink.withValues(alpha: 0.6),
                              ),
                            ),
                            const SizedBox(height: 3),
                            Container(
                              padding: const EdgeInsets.symmetric(
                                horizontal: 5,
                                vertical: 2,
                              ),
                              decoration: BoxDecoration(
                                color: active ? river : Colors.transparent,
                                borderRadius: BorderRadius.circular(9),
                              ),
                              child: Text(
                                '${date.day}',
                                style: TextStyle(
                                  fontSize: 11,
                                  fontWeight: FontWeight.w700,
                                  color: active ? Colors.white : ink,
                                ),
                              ),
                            ),
                          ],
                        ),
                      );
                    }),
                  ),
                ),
                SizedBox(
                  height: height,
                  child: Stack(
                    children: [
                      for (var i = 0; i < 7; i++)
                        Positioned(
                          left: i * width,
                          top: 0,
                          width: width,
                          height: height,
                          child: DecoratedBox(
                            decoration: BoxDecoration(
                              color: i < 5
                                  ? Colors.white.withValues(alpha: 0.45)
                                  : river.withValues(alpha: 0.025),
                              border: Border(
                                left: BorderSide(
                                  color: ink.withValues(alpha: 0.04),
                                ),
                              ),
                            ),
                          ),
                        ),
                      for (var p = 1; p <= 11; p++)
                        Positioned(
                          left: 0,
                          right: 0,
                          top: top(p),
                          child: Divider(
                            height: 1,
                            color: ink.withValues(alpha: 0.055),
                          ),
                        ),
                      for (final e in events)
                        if (groups[e]!.first == e)
                          _block(context, groups[e]!, width, rowHeight, top),
                    ],
                  ),
                ),
              ],
            ),
          ),
        ],
      );
    },
  );

  Widget _block(
    BuildContext context,
    List<CourseOccurrence> group,
    double width,
    double rowHeight,
    double Function(int) top,
  ) {
    final first = group.map((e) => e.course.startPeriod).reduce(math.min);
    final last = group.map((e) => e.course.endPeriod).reduce(math.max);
    return Positioned(
      left: (group.first.course.weekday - 1) * width + 2,
      top: top(first) + 4,
      width: width - 4,
      height: (last - first + 1) * rowHeight - 8,
      child: group.length == 1
          ? _entry(context, group.first)
          : Container(
              decoration: BoxDecoration(
                color: river.withValues(alpha: 0.06),
                borderRadius: BorderRadius.circular(8),
                border: Border.all(color: river.withValues(alpha: 0.15)),
              ),
              // Conflict entries are explicitly a list, with their own lesson ranges.
              // They are not separate time-scaled bars squeezed into narrow lanes.
              child: Column(
                children: [
                  const Padding(
                    padding: EdgeInsets.symmetric(horizontal: 3, vertical: 3),
                    child: Text(
                      '冲突列表',
                      style: TextStyle(
                        fontSize: 9.5,
                        height: 1.22,
                        color: Color(0xFFB45D54),
                      ),
                    ),
                  ),
                  for (final e in group)
                    Expanded(child: _entry(context, e, inConflict: true)),
                ],
              ),
            ),
    );
  }

  Widget _entry(
    BuildContext context,
    CourseOccurrence e, {
    bool inConflict = false,
  }) => Semantics(
    label: '${e.course.name}，${e.course.teacher}，${e.course.room}',
    button: true,
    excludeSemantics: true,
    onTap: () => showCourseDetails(context, e),
    child: GestureDetector(
      onTap: () => showCourseDetails(context, e),
      child: Container(
        width: double.infinity,
        padding: const EdgeInsets.symmetric(horizontal: 3, vertical: 6),
        decoration: inConflict
            ? null
            : BoxDecoration(
                color: courseColor(e.course.id, settings),
                borderRadius: BorderRadius.circular(8),
                border: Border.all(color: Colors.white.withValues(alpha: 0.8)),
              ),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            Text(
              e.course.name,
              maxLines: 2,
              overflow: TextOverflow.ellipsis,
              style: _nameStyle,
            ),
            if (inConflict) ...[
              const SizedBox(height: 3),
              Text(
                '${e.course.startPeriod}–${e.course.endPeriod}节',
                style: _metadataStyle,
              ),
            ],
            const SizedBox(height: 4),
            Text(
              e.course.teacher,
              style: _metadataStyle.copyWith(
                color: ink.withValues(alpha: 0.85),
              ),
            ),
            const SizedBox(height: 3),
            Text(
              e.course.room,
              style: _metadataStyle.copyWith(color: ink.withValues(alpha: 0.7)),
            ),
          ],
        ),
      ),
    ),
  );
}