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

import '../../../providers/programmer_day_data_provider.dart';
import '../../../providers/programmer_tasks_provider.dart';
import '../../../widgets/app_section_header.dart';
import 'monitor_model.dart';

final _dateFmt = DateFormat('EEE, MMM d');

/// Side panel that shows "who's helping whom" for a selected day, with a
/// ← / → stepper that cannot advance past today.
///
/// Uses a [ValueNotifier<DateTime>] initialized to [todayKeyProvider] so the
/// displayed day is independent of the parent; the family provider is
/// re-watched whenever the day changes.
class HelpPanel extends ConsumerStatefulWidget {
  const HelpPanel({super.key, this.profileNames = const {}});

  final Map<String, String> profileNames;

  @override
  ConsumerState<HelpPanel> createState() => _HelpPanelState();
}

class _HelpPanelState extends ConsumerState<HelpPanel> {
  late final ValueNotifier<DateTime> _day;

  @override
  void initState() {
    super.initState();
    final today = ref.read(todayKeyProvider);
    _day = ValueNotifier(today);
  }

  @override
  void dispose() {
    _day.dispose();
    super.dispose();
  }

  void _stepDay(int delta) {
    final today = ref.read(todayKeyProvider);
    final next = _day.value.add(Duration(days: delta));
    if (delta > 0 && !next.isBefore(today) && next != today) return;
    if (delta > 0 && next.isAfter(today)) return;
    setState(() {
      _day.value = next;
    });
  }

  @override
  Widget build(BuildContext context) {
    final cs = Theme.of(context).colorScheme;
    final tt = Theme.of(context).textTheme;
    final today = ref.watch(todayKeyProvider);
    final tasksAsync = ref.watch(programmerTasksProvider);
    final dayDataAsync = ref.watch(programmerDayDataProvider(_day.value));

    final isAtToday = !_day.value.isBefore(today);

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        const AppSectionHeader("Who's helping whom"),
        // Day stepper
        Row(
          mainAxisSize: MainAxisSize.min,
          children: [
            IconButton(
              icon: const Icon(Icons.chevron_left),
              onPressed: () => _stepDay(-1),
              tooltip: 'Previous day',
            ),
            Text(
              _dateFmt.format(_day.value),
              style: tt.labelMedium?.copyWith(color: cs.onSurface),
            ),
            IconButton(
              icon: Icon(
                Icons.chevron_right,
                color: isAtToday ? cs.onSurface.withValues(alpha: 0.3) : null,
              ),
              onPressed: isAtToday ? null : () => _stepDay(1),
              tooltip: 'Next day',
            ),
          ],
        ),
        const SizedBox(height: 8),
        // Help edges
        Expanded(
          child: Builder(
            builder: (context) {
              if (dayDataAsync.isLoading && !dayDataAsync.hasValue) {
                return const Center(child: CircularProgressIndicator());
              }

              final dayData = dayDataAsync.valueOrNull;
              if (dayData == null) {
                return _emptyText(
                  'No data for this day.',
                  cs: cs,
                  tt: tt,
                );
              }

              final tasks = tasksAsync.valueOrNull ?? [];
              final taskById = {for (final t in tasks) t.id: t};

              final edges = buildHelpEdges(
                workLogs: dayData.workLogs,
                taskById: taskById,
                day: _day.value,
              );

              if (edges.isEmpty) {
                return _emptyText(
                  'No help logged this day.',
                  cs: cs,
                  tt: tt,
                );
              }

              return ListView.separated(
                itemCount: edges.length,
                separatorBuilder: (_, _) => const Divider(height: 1),
                itemBuilder: (context, i) {
                  final e = edges[i];
                  final names = widget.profileNames;
                  final helperName = names[e.helperId] ?? e.helperId;
                  final assigneeName = names[e.assigneeId] ?? e.assigneeId;
                  final timeStr = TimeOfDay.fromDateTime(e.at).format(context);
                  return Padding(
                    padding: const EdgeInsets.symmetric(vertical: 6),
                    child: Text(
                      '$helperName → $assigneeName · ${e.taskTitle} · ${e.minutes}m · $timeStr',
                      style: tt.bodySmall?.copyWith(color: cs.onSurface),
                    ),
                  );
                },
              );
            },
          ),
        ),
      ],
    );
  }

  Widget _emptyText(
    String msg, {
    required ColorScheme cs,
    required TextTheme tt,
  }) {
    return Center(
      child: Text(
        msg,
        style: tt.bodySmall?.copyWith(color: cs.onSurfaceVariant),
      ),
    );
  }
}