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

import '../../../providers/reports_provider.dart';
import 'report_card_wrapper.dart';

/// Grouped vertical bar chart — assigned vs completed tasks per IT staff member.
class StaffWorkloadChart extends ConsumerWidget {
  const StaffWorkloadChart({super.key, this.repaintKey});
  final GlobalKey? repaintKey;

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final asyncData = ref.watch(staffWorkloadReportProvider);

    return asyncData.when(
      loading: () => ReportCardWrapper(
        title: 'IT Staff Workload',
        isLoading: true,
        height: 300,
        repaintBoundaryKey: repaintKey,
        child: const SizedBox.shrink(),
      ),
      error: (e, _) => ReportCardWrapper(
        title: 'IT Staff Workload',
        error: e.toString(),
        repaintBoundaryKey: repaintKey,
        child: const SizedBox.shrink(),
      ),
      data: (data) => _build(context, data),
    );
  }

  Widget _build(BuildContext context, List<StaffWorkload> data) {
    if (data.isEmpty) {
      return ReportCardWrapper(
        title: 'IT Staff Workload',
        repaintBoundaryKey: repaintKey,
        child: const SizedBox(
          height: 200,
          child: Center(child: Text('No data for selected period')),
        ),
      );
    }

    final colors = Theme.of(context).colorScheme;
    final text = Theme.of(context).textTheme;

    final maxY = data.fold<int>(
      0,
      (m, e) => [
        m,
        e.assignedCount,
        e.completedCount,
      ].reduce((a, b) => a > b ? a : b),
    );

    return ReportCardWrapper(
      title: 'IT Staff Workload',
      repaintBoundaryKey: repaintKey,
      height: 320,
      child: Column(
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              _LegendDot(color: colors.primary, label: 'Assigned'),
              const SizedBox(width: 16),
              _LegendDot(color: colors.tertiary, label: 'Completed'),
            ],
          ),
          const SizedBox(height: 12),
          Expanded(
            child: BarChart(
              BarChartData(
                alignment: BarChartAlignment.spaceAround,
                maxY: maxY * 1.2,
                barTouchData: BarTouchData(
                  touchTooltipData: BarTouchTooltipData(
                    getTooltipItem: (group, groupIdx, rod, rodIdx) {
                      final item = data[group.x];
                      final label = rodIdx == 0 ? 'Assigned' : 'Completed';
                      return BarTooltipItem(
                        '${item.staffName}\n$label: ${rod.toY.toInt()}',
                        text.bodySmall!.copyWith(
                          color: colors.onInverseSurface,
                        ),
                      );
                    },
                  ),
                ),
                titlesData: FlTitlesData(
                  leftTitles: AxisTitles(
                    sideTitles: SideTitles(
                      showTitles: true,
                      reservedSize: 36,
                      getTitlesWidget: (value, meta) => Text(
                        value.toInt().toString(),
                        style: text.labelSmall,
                      ),
                    ),
                  ),
                  bottomTitles: AxisTitles(
                    sideTitles: SideTitles(
                      showTitles: true,
                      getTitlesWidget: (value, meta) {
                        final idx = value.toInt();
                        if (idx < 0 || idx >= data.length) {
                          return const SizedBox.shrink();
                        }
                        final name = data[idx].staffName;
                        // Show first name only to save space
                        final short = name.split(' ').first;
                        return Padding(
                          padding: const EdgeInsets.only(top: 6),
                          child: Text(
                            short.length > 10
                                ? '${short.substring(0, 8)}…'
                                : short,
                            style: text.labelSmall,
                          ),
                        );
                      },
                    ),
                  ),
                  topTitles: const AxisTitles(
                    sideTitles: SideTitles(showTitles: false),
                  ),
                  rightTitles: const AxisTitles(
                    sideTitles: SideTitles(showTitles: false),
                  ),
                ),
                gridData: FlGridData(
                  drawVerticalLine: false,
                  horizontalInterval: maxY > 0 ? (maxY / 4).ceilToDouble() : 1,
                ),
                borderData: FlBorderData(show: false),
                barGroups: List.generate(data.length, (i) {
                  return BarChartGroupData(
                    x: i,
                    barsSpace: 4,
                    barRods: [
                      BarChartRodData(
                        toY: data[i].assignedCount.toDouble(),
                        width: 14,
                        borderRadius: const BorderRadius.vertical(
                          top: Radius.circular(4),
                        ),
                        color: colors.primary,
                      ),
                      BarChartRodData(
                        toY: data[i].completedCount.toDouble(),
                        width: 14,
                        borderRadius: const BorderRadius.vertical(
                          top: Radius.circular(4),
                        ),
                        color: colors.tertiary,
                      ),
                    ],
                  );
                }),
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _LegendDot extends StatelessWidget {
  const _LegendDot({required this.color, required this.label});
  final Color color;
  final String label;

  @override
  Widget build(BuildContext context) {
    return Row(
      mainAxisSize: MainAxisSize.min,
      children: [
        Container(
          width: 10,
          height: 10,
          decoration: BoxDecoration(color: color, shape: BoxShape.circle),
        ),
        const SizedBox(width: 4),
        Text(label, style: Theme.of(context).textTheme.bodySmall),
      ],
    );
  }
}