import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:mileograph_flutter/objects/objects.dart';
import 'package:mileograph_flutter/services/data_service.dart';
import 'package:provider/provider.dart';

class LatestLocoChangesPanel extends StatefulWidget {
  const LatestLocoChangesPanel({super.key, this.expanded = false});

  final bool expanded;

  @override
  State<LatestLocoChangesPanel> createState() => _LatestLocoChangesPanelState();
}

class _LatestLocoChangesPanelState extends State<LatestLocoChangesPanel> {
  late final ScrollController _controller;
  final Set<String> _collapsedDates = {};
  final Set<String> _collapsedClasses = {};
  final Set<String> _collapsedLocos = {};

  @override
  void initState() {
    super.initState();
    _controller = ScrollController();
  }

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

  @override
  Widget build(BuildContext context) {
    final data = context.watch<DataService>();
    final changes = data.latestLocoChanges;
    final isLoading = data.isLatestLocoChangesLoading;
    final hasMore = data.latestLocoChangesHasMore;
    final textTheme = Theme.of(context).textTheme;

    return Card(
      clipBehavior: Clip.antiAlias,
      child: Padding(
        padding: const EdgeInsets.all(16),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              Row(
                children: [
                const Icon(Icons.bolt, size: 20),
                const SizedBox(width: 8),
                Expanded(
                  child: Text(
                    'Latest loco changes',
                    style: textTheme.titleMedium?.copyWith(
                      fontWeight: FontWeight.w800,
                    ),
                  ),
                ),
                if (isLoading && changes.isNotEmpty)
                  const SizedBox(
                    width: 18,
                    height: 18,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  ),
              ],
            ),
            const SizedBox(height: 8),
            if (isLoading && changes.isEmpty)
              const Padding(
                padding: EdgeInsets.all(12.0),
                child: Center(child: CircularProgressIndicator()),
              )
            else if (changes.isEmpty)
              Padding(
                padding: const EdgeInsets.symmetric(vertical: 8.0),
                child: Text(
                  'No recent loco changes yet.',
                  style: textTheme.bodyMedium,
                ),
              )
            else
              Column(
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  _buildChangesList(changes, textTheme),
                  const SizedBox(height: 8),
                  Align(
                    alignment: Alignment.centerLeft,
                    child: OutlinedButton.icon(
                      onPressed: isLoading ? null : _loadMore,
                      icon: isLoading
                          ? const SizedBox(
                              height: 14,
                              width: 14,
                              child: CircularProgressIndicator(strokeWidth: 2),
                            )
                          : const Icon(Icons.expand_more),
                      label: Text(isLoading ? 'Loading...' : 'Show more'),
                    ),
                  ),
                ],
              ),
          ],
        ),
      ),
    );
  }

  Widget _buildChangesList(List<LocoChange> changes, TextTheme textTheme) {
    final grouped = _groupChanges(changes);
    // Start with all locos collapsed by default.
    if (_collapsedLocos.isEmpty) {
      for (final group in grouped) {
        for (final classGroup in group.classGroups) {
          for (final locoGroup in classGroup.locoGroups) {
            _collapsedLocos.add(
              _locoKey(group.dateLabel, classGroup.classLabel, locoGroup.locoLabel),
            );
          }
        }
      }
    }

    final listView = ListView.separated(
      controller: null,
      shrinkWrap: true,
      physics: const NeverScrollableScrollPhysics(),
      itemBuilder: (context, groupIndex) {
        final group = grouped[groupIndex];
        final dateCollapsed = _collapsedDates.contains(group.dateLabel);
        return Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            Padding(
              padding: const EdgeInsets.symmetric(vertical: 6.0),
              child: Row(
                children: [
                  IconButton(
                    iconSize: 18,
                    padding: EdgeInsets.zero,
                    constraints: const BoxConstraints(),
                    onPressed: () => _toggleDate(group.dateLabel),
                    icon: Icon(
                      dateCollapsed ? Icons.chevron_right : Icons.expand_more,
                    ),
                  ),
                  const SizedBox(width: 6),
                  Expanded(
                    child: Text(
                      group.dateLabel,
                      style: textTheme.labelLarge?.copyWith(
                        fontWeight: FontWeight.w700,
                      ),
                    ),
                  ),
                  TextButton(
                    onPressed: () => _collapseDateChildren(
                      group.dateLabel,
                      group.classGroups,
                      collapse: !_isDateFullyCollapsed(group),
                    ),
                    child: Text(
                      _isDateFullyCollapsed(group) ? 'Expand all' : 'Collapse all',
                    ),
                  ),
                ],
              ),
            ),
            if (!dateCollapsed)
              ...group.classGroups.map(
                (classGroup) {
                  final classKey = _classKey(group.dateLabel, classGroup.classLabel);
                  final classCollapsed = _collapsedClasses.contains(classKey);
                  return Padding(
                    padding: const EdgeInsets.only(bottom: 8.0, left: 12.0),
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Row(
                          children: [
                            IconButton(
                              iconSize: 18,
                              padding: EdgeInsets.zero,
                              constraints: const BoxConstraints(),
                              onPressed: () => _toggleClass(classKey),
                              icon: Icon(
                                classCollapsed
                                    ? Icons.chevron_right
                                    : Icons.expand_more,
                              ),
                            ),
                            const SizedBox(width: 4),
                            Expanded(
                              child: Text(
                                classGroup.classLabel,
                                style: textTheme.titleSmall?.copyWith(
                                  fontWeight: FontWeight.w700,
                                ),
                              ),
                            ),
                            TextButton(
                              onPressed: () => _collapseClassChildren(
                                group.dateLabel,
                                classGroup.classLabel,
                                classGroup.locoGroups,
                                collapse:
                                    !_isClassFullyCollapsed(classKey, classGroup, group.dateLabel),
                              ),
                              child: Text(
                                _isClassFullyCollapsed(classKey, classGroup, group.dateLabel)
                                    ? 'Expand all'
                                    : 'Collapse all',
                              ),
                            ),
                          ],
                        ),
                        if (!classCollapsed)
                          ...classGroup.locoGroups.map(
                            (locoGroup) {
                              final locoKey =
                                  _locoKey(group.dateLabel, classGroup.classLabel, locoGroup.locoLabel);
                              final locoCollapsed = _collapsedLocos.contains(locoKey);
                              return Padding(
                                padding:
                                    const EdgeInsets.only(bottom: 4.0, left: 22.0),
                                child: Column(
                                  crossAxisAlignment: CrossAxisAlignment.start,
                                  children: [
                                    Row(
                                      children: [
                                        IconButton(
                                          iconSize: 18,
                                          padding: EdgeInsets.zero,
                                          constraints: const BoxConstraints(),
                                          onPressed: () => _toggleLoco(locoKey),
                                          icon: Icon(
                                            locoCollapsed
                                                ? Icons.chevron_right
                                                : Icons.expand_more,
                                          ),
                                        ),
                                        const SizedBox(width: 4),
                                        Text(
                                          locoGroup.locoLabel,
                                          style: textTheme.bodyMedium?.copyWith(
                                            fontWeight: FontWeight.w700,
                                          ),
                                        ),
                                      ],
                                    ),
                                    if (!locoCollapsed) ...[
                                      const SizedBox(height: 2),
                                      ...locoGroup.changes.map(
                                        (change) => ListTile(
                                          dense: true,
                                          visualDensity: const VisualDensity(
                                            horizontal: 0,
                                            vertical: -3,
                                          ),
                                          minVerticalPadding: 0,
                                          contentPadding: EdgeInsets.zero,
                                          title: Text(
                                            '${change.changeLabel}: ${change.valueLabel}',
                                            style: textTheme.bodyMedium,
                                          ),
                                          trailing: change.approvedBy.isEmpty
                                              ? null
                                              : Text(
                                                  change.approvedBy,
                                                  style: textTheme.labelSmall,
                                                ),
                                        ),
                                      ),
                                    ],
                                  ],
                                ),
                              );
                            },
                          ),
                      ],
                    ),
                  );
                },
              ),
          ],
        );
      },
      separatorBuilder: (_, __) => const Divider(height: 8),
      itemCount: grouped.length,
    );

    if (widget.expanded) {
      return listView;
    }

    return listView;
  }

  void _toggleDate(String date) {
    setState(() {
      if (_collapsedDates.contains(date)) {
        _collapsedDates.remove(date);
      } else {
        _collapsedDates.add(date);
      }
    });
  }

  void _toggleClass(String key) {
    setState(() {
      if (_collapsedClasses.contains(key)) {
        _collapsedClasses.remove(key);
      } else {
        _collapsedClasses.add(key);
      }
    });
  }

  void _toggleLoco(String key) {
    setState(() {
      if (_collapsedLocos.contains(key)) {
        _collapsedLocos.remove(key);
      } else {
        _collapsedLocos.add(key);
      }
    });
  }

  void _collapseDateChildren(
    String date,
    List<_ClassGroup> classGroups, {
    required bool collapse,
  }) {
    setState(() {
      for (final classGroup in classGroups) {
        final classKey = _classKey(date, classGroup.classLabel);
        if (collapse) {
          _collapsedClasses.add(classKey);
        } else {
          _collapsedClasses.remove(classKey);
        }
        for (final locoGroup in classGroup.locoGroups) {
          final locoKey = _locoKey(date, classGroup.classLabel, locoGroup.locoLabel);
          if (collapse) {
            _collapsedLocos.add(locoKey);
          } else {
            _collapsedLocos.remove(locoKey);
          }
        }
      }
    });
  }

  void _collapseClassChildren(
    String date,
    String classLabel,
    List<_LocoGroup> locos, {
    required bool collapse,
  }) {
    setState(() {
      final classKey = _classKey(date, classLabel);
      if (collapse) {
        _collapsedClasses.add(classKey);
      } else {
        _collapsedClasses.remove(classKey);
      }
      for (final locoGroup in locos) {
        final locoKey = _locoKey(date, classLabel, locoGroup.locoLabel);
        if (collapse) {
          _collapsedLocos.add(locoKey);
        } else {
          _collapsedLocos.remove(locoKey);
        }
      }
    });
  }

  bool _isDateFullyCollapsed(_ChangeGroup group) {
    for (final classGroup in group.classGroups) {
      final classKey = _classKey(group.dateLabel, classGroup.classLabel);
      if (!_collapsedClasses.contains(classKey)) return false;
      for (final loco in classGroup.locoGroups) {
        final locoKey = _locoKey(group.dateLabel, classGroup.classLabel, loco.locoLabel);
        if (!_collapsedLocos.contains(locoKey)) return false;
      }
    }
    return true;
  }

  bool _isClassFullyCollapsed(String classKey, _ClassGroup classGroup, String date) {
    if (!_collapsedClasses.contains(classKey)) return false;
    for (final loco in classGroup.locoGroups) {
      final locoKey = _locoKey(date, classGroup.classLabel, loco.locoLabel);
      if (!_collapsedLocos.contains(locoKey)) return false;
    }
    return true;
  }

  String _classKey(String date, String classLabel) => '$date|$classLabel';
  String _locoKey(String date, String classLabel, String locoLabel) =>
      '$date|$classLabel|$locoLabel';

  List<_ChangeGroup> _groupChanges(List<LocoChange> changes) {
    final dateFormat = DateFormat('yyyy-MM-dd');
    final Map<String, Map<String, Map<String, List<LocoChange>>>> grouped = {};

    final filtered = changes.where((change) {
      final code = change.attrCode.toLowerCase();
      return code != 'build_prec' && code != 'operational' && code != 'gettable';
    });

    for (final change in filtered) {
      final date = change.approvedAt ?? change.validFrom;
      final dateKey = date != null ? dateFormat.format(date) : 'Unknown date';
      final classKey = change.locoClass.isNotEmpty
          ? change.locoClass
          : 'Unknown class';
      final locoKey = _locoLabel(change);
      grouped.putIfAbsent(dateKey, () => {});
      grouped[dateKey]!.putIfAbsent(classKey, () => {});
      grouped[dateKey]![classKey]!.putIfAbsent(locoKey, () => []);
      grouped[dateKey]![classKey]![locoKey]!.add(change);
    }

    final sortedDates = grouped.keys.toList()
      ..sort((a, b) {
        if (a == 'Unknown date') return 1;
        if (b == 'Unknown date') return -1;
        return b.compareTo(a); // newest first
      });

    return sortedDates
        .map(
          (dateKey) => _ChangeGroup(
            dateLabel: dateKey,
            classGroups: grouped[dateKey]!.entries
                .map(
                  (classEntry) => _ClassGroup(
                    classLabel: classEntry.key,
                    locoGroups: classEntry.value.entries
                        .map(
                          (locoEntry) => _LocoGroup(
                            locoLabel: locoEntry.key,
                            changes: locoEntry.value
                              ..sort(
                                (a, b) => (b.approvedAt ?? b.validFrom ?? DateTime(0))
                                    .compareTo(a.approvedAt ?? a.validFrom ?? DateTime(0)),
                              ),
                          ),
                        )
                        .toList(),
                  ),
                )
                .toList(),
          ),
        )
        .toList();
  }

  Future<void> _loadMore() async {
    final data = context.read<DataService>();
    await data.fetchLatestLocoChanges(
      offset: data.latestLocoChanges.length,
      append: true,
    );
  }
}

class _ChangeGroup {
  final String dateLabel;
  final List<_ClassGroup> classGroups;

  _ChangeGroup({required this.dateLabel, required this.classGroups});
}

class _LocoGroup {
  final String locoLabel;
  final List<LocoChange> changes;

  _LocoGroup({required this.locoLabel, required this.changes});
}

class _ClassGroup {
  final String classLabel;
  final List<_LocoGroup> locoGroups;

  _ClassGroup({required this.classLabel, required this.locoGroups});
}

String _locoLabel(LocoChange change) {
  final number = change.locoNumber.trim();
  final name = change.locoName.trim();
  if (number.isNotEmpty && name.isNotEmpty) return '$number — $name';
  if (number.isNotEmpty) return number;
  if (name.isNotEmpty) return name;
  return 'Loco ${change.locoId}';
}