part of 'package:mileograph_flutter/components/pages/loco_timeline.dart';

final DateFormat _dateFormat = DateFormat('yyyy-MM-dd');

enum _PendingModerationAction { approve, reject }

class _TimelineGrid extends StatefulWidget {
  const _TimelineGrid({
    required this.entries,
    this.onEditEntry,
    this.onDeleteEntry,
    this.onModeratePending,
    this.pendingActionEventIds = const {},
    this.expandedPendingAttrs = const {},
    this.onTogglePendingAttr,
  });

  final List<LocoAttrVersion> entries;
  final void Function(LocoAttrVersion entry)? onEditEntry;
  final void Function(LocoAttrVersion entry)? onDeleteEntry;
  final Future<void> Function(
    LocoAttrVersion entry,
    _PendingModerationAction action,
  )? onModeratePending;
  final Set<int> pendingActionEventIds;
  final Set<String> expandedPendingAttrs;
  final void Function(String attrCode)? onTogglePendingAttr;

  @override
  State<_TimelineGrid> createState() => _TimelineGridState();
}

class _TimelineGridState extends State<_TimelineGrid> {
  final ScrollController _horizontalController = ScrollController();
  final ScrollController _rightVerticalController = ScrollController();
  final ScrollController _leftVerticalController = ScrollController();
  bool _isSyncingScroll = false;
  double _scrollOffset = 0;

  @override
  void initState() {
    super.initState();
    _rightVerticalController.addListener(_syncVerticalScroll);
    _horizontalController.addListener(_onHorizontalScroll);
  }

  @override
  void dispose() {
    _rightVerticalController.removeListener(_syncVerticalScroll);
    _horizontalController.removeListener(_onHorizontalScroll);
    _horizontalController.dispose();
    _rightVerticalController.dispose();
    _leftVerticalController.dispose();
    super.dispose();
  }

  void _syncVerticalScroll() {
    if (_isSyncingScroll) return;
    if (!_leftVerticalController.hasClients ||
        !_rightVerticalController.hasClients) {
      return;
    }
    _isSyncingScroll = true;
    _leftVerticalController.jumpTo(
      _rightVerticalController.offset.clamp(
        0.0,
        _leftVerticalController.position.maxScrollExtent,
      ),
    );
    _isSyncingScroll = false;
  }

  void _onHorizontalScroll() {
    if (!mounted) return;
    setState(() {
      _scrollOffset = _horizontalController.offset;
    });
  }

  @override
  Widget build(BuildContext context) {
    final filteredEntries = widget.entries.where((e) {
      final code = e.attrCode.toLowerCase();
      return !{
        'operational',
        'gettable',
        'build_prec',
        'build_year',
        'build_month',
        'build_day',
      }.contains(code);
    }).toList();
    final model = _TimelineModel.fromEntries(
      filteredEntries,
      expandedAttrCodes: widget.expandedPendingAttrs,
    );
    final axisSegments = model.axisSegments;
    const labelWidth = 110.0;
    const rowHeight = 52.0;
    const double axisHeight = 48;
    final rows = model.rows;
    final totalRowsHeight = rows.length * rowHeight;
    final axisWidth = math.max(model.axisTotalWidth, 120.0);
    final double viewHeight = totalRowsHeight + axisHeight + 8;

    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      mainAxisSize: MainAxisSize.min,
      children: [
        SizedBox(
          height: viewHeight,
          child: Row(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              SizedBox(
                width: labelWidth,
                child: Column(
                  children: [
                    SizedBox(
                      height: axisHeight,
                      child: Align(
                        alignment: Alignment.centerLeft,
                        child: Text(
                          'Attribute',
                          style: Theme.of(context).textTheme.labelLarge?.copyWith(
                                fontWeight: FontWeight.w700,
                              ),
                        ),
                      ),
                    ),
                    Expanded(
                      child: Scrollbar(
                        controller: _leftVerticalController,
                        thumbVisibility: true,
                        child: ListView.builder(
                          controller: _leftVerticalController,
                          physics: const NeverScrollableScrollPhysics(),
                          itemExtent: rowHeight,
                          itemCount: rows.length,
                          itemBuilder: (_, index) {
                            final row = rows[index];
                            final label = row.isPrimary
                                ? _formatAttrLabel(row.attrCode)
                                : (row.pendingUser?.trim().isNotEmpty == true
                                    ? row.pendingUser!.trim()
                                    : 'Unknown');
                            return Container(
                              alignment: Alignment.centerLeft,
                              padding: const EdgeInsets.symmetric(
                                horizontal: 10,
                              ),
                              decoration: BoxDecoration(
                                color: Theme.of(context)
                                    .colorScheme
                                    .surfaceContainerHighest,
                                border: Border(
                                  bottom: BorderSide(
                                    color:
                                        Theme.of(context).colorScheme.outlineVariant,
                                  ),
                                ),
                              ),
                              child: Row(
                                children: [
                                  if (!row.isPrimary) ...[
                                    Icon(
                                      Icons.subdirectory_arrow_right,
                                      size: 16,
                                      color: Theme.of(context).hintColor,
                                    ),
                                    const SizedBox(width: 6),
                                  ],
                                  Expanded(
                                    child: Text(
                                      label,
                                      maxLines: 1,
                                      overflow: TextOverflow.ellipsis,
                                      style: Theme.of(context)
                                          .textTheme
                                          .labelLarge
                                          ?.copyWith(
                                            fontWeight: row.isPrimary
                                                ? FontWeight.w700
                                                : FontWeight.w600,
                                          ),
                                    ),
                                  ),
                                  if (row.showExpandToggle)
                                    IconButton(
                                      onPressed: widget.onTogglePendingAttr == null
                                          ? null
                                          : () => widget.onTogglePendingAttr?.call(
                                                row.attrCode,
                                              ),
                                      icon: Icon(
                                        row.isExpanded
                                            ? Icons.expand_less
                                            : Icons.expand_more,
                                      ),
                                      tooltip: row.isExpanded
                                          ? 'Collapse pending rows'
                                          : 'Expand pending rows',
                                      visualDensity: VisualDensity.compact,
                                    ),
                                ],
                              ),
                            );
                          },
                        ),
                      ),
                    ),
                  ],
                ),
              ),
              const SizedBox(width: 8),
              Expanded(
                child: Scrollbar(
                  controller: _horizontalController,
                  thumbVisibility: true,
                  child: SingleChildScrollView(
                    controller: _horizontalController,
                    scrollDirection: Axis.horizontal,
                    child: SizedBox(
                      width: axisWidth,
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: [
                          _AxisRow(
                            segments: axisSegments,
                            totalWidth: axisWidth,
                            endLabel: model.endLabel,
                          ),
                          const SizedBox(height: 8),
                          Expanded(
                            child: ListView.builder(
                              controller: _rightVerticalController,
                              itemExtent: rowHeight,
                              itemCount: rows.length,
                              itemBuilder: (_, index) {
                                final blocks = rows[index].blocks;
                                return Padding(
                                  padding:
                                      const EdgeInsets.symmetric(vertical: 2.0),
                                  child: _AttrRow(
                                    rowHeight: rowHeight,
                                    blocks: blocks,
                                    model: model,
                                    scrollOffset: _scrollOffset,
                                    viewportWidth: axisWidth,
                                    onEditEntry: widget.onEditEntry,
                                    onDeleteEntry: widget.onDeleteEntry,
                                    onModeratePending: widget.onModeratePending,
                                    pendingActionEventIds: widget.pendingActionEventIds,
                                  ),
                                );
                              },
                            ),
                          ),
                        ],
                      ),
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ],
    );
  }
}

class _AxisRow extends StatelessWidget {
  const _AxisRow({
    required this.segments,
    required this.endLabel,
    required this.totalWidth,
  });

  final List<_AxisSegment> segments;
  final String endLabel;
  final double totalWidth;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    const double axisHeight = 48;
    return SizedBox(
      width: totalWidth,
      height: axisHeight,
      child: Stack(
        children: [
          for (int i = 0; i < segments.length; i++) ...[
            Positioned(
              left: segments[i].offset,
              width: segments[i].width,
              top: 0,
              bottom: 0,
              child: Align(
                alignment: Alignment.centerLeft,
                child: Text(
                  segments[i].label,
                  overflow: TextOverflow.ellipsis,
                  maxLines: 1,
                  style: theme.textTheme.labelSmall,
                ),
              ),
            ),
          ],
          Positioned(
            right: 0,
            top: 0,
            bottom: 0,
            child: Align(
              alignment: Alignment.centerRight,
              child: Text(
                endLabel,
                overflow: TextOverflow.ellipsis,
                maxLines: 1,
                style: theme.textTheme.labelSmall,
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class _AttrRow extends StatelessWidget {
  const _AttrRow({
    required this.rowHeight,
    required this.blocks,
    required this.model,
    required this.scrollOffset,
    required this.viewportWidth,
    this.onEditEntry,
    this.onDeleteEntry,
    this.onModeratePending,
    this.pendingActionEventIds = const {},
  });

  final double rowHeight;
  final List<_ValueBlock> blocks;
  final _TimelineModel model;
  final double scrollOffset;
  final double viewportWidth;
  final void Function(LocoAttrVersion entry)? onEditEntry;
  final void Function(LocoAttrVersion entry)? onDeleteEntry;
  final Future<void> Function(
    LocoAttrVersion entry,
    _PendingModerationAction action,
  )? onModeratePending;
  final Set<int> pendingActionEventIds;

  @override
  Widget build(BuildContext context) {
    final width = math.max(model.axisTotalWidth, 120.0);
    final activeBlock = _activeBlock(blocks, scrollOffset);
    final double stickyWidth = activeBlock == null
        ? 0
        : (activeBlock.right - scrollOffset).clamp(20.0, viewportWidth);

    return SizedBox(
      width: width,
      height: rowHeight,
      child: Stack(
        clipBehavior: Clip.hardEdge,
        children: [
          for (final block in blocks)
            Positioned(
              left: block.left,
              width: block.width,
              top: 0,
              bottom: 0,
              child: _ValueBlockMenu(
                block: block,
                onEditEntry: onEditEntry,
                onDeleteEntry: onDeleteEntry,
                onModeratePending: onModeratePending,
                pendingActionEventIds: pendingActionEventIds,
              ),
            ),
          if (activeBlock != null)
            Positioned(
              left: scrollOffset,
              width: stickyWidth,
              top: 0,
              bottom: 0,
              child: IgnorePointer(
                child: ClipRect(
                  child: _ValueBlockView(
                    block: activeBlock.copyWith(
                      left: scrollOffset,
                      width: stickyWidth,
                    ),
                    clipLeftEdge: scrollOffset > activeBlock.left + 0.1,
                    pendingActionEventIds: pendingActionEventIds,
                  ),
                ),
              ),
            ),
        ],
      ),
    );
  }

  _ValueBlock? _activeBlock(List<_ValueBlock> blocks, double offset) {
    for (final block in blocks) {
      if (offset >= block.left && offset < block.right) return block;
    }
    return null;
  }
}

class _ValueBlockView extends StatelessWidget {
  const _ValueBlockView({
    required this.block,
    this.clipLeftEdge = false,
    this.pendingActionEventIds = const {},
  });

  final _ValueBlock block;
  final bool clipLeftEdge;
  final Set<int> pendingActionEventIds;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final color = block.cell.color;
    final textColor = ThemeData.estimateBrightnessForColor(color) ==
            Brightness.dark
        ? Colors.white
        : Colors.black87;

    final entry = block.entry;
    final eventId = entry?.sourceEventId;
    final isPendingAction =
        entry?.isPending == true && eventId != null && pendingActionEventIds.contains(eventId);

    final radius = BorderRadius.only(
      topLeft: Radius.circular(clipLeftEdge ? 0 : 12),
      bottomLeft: Radius.circular(clipLeftEdge ? 0 : 12),
      topRight: const Radius.circular(12),
      bottomRight: const Radius.circular(12),
    );

    return ClipRRect(
      borderRadius: radius,
      child: Container(
        padding: const EdgeInsets.symmetric(horizontal: 10, vertical: 8),
        decoration: BoxDecoration(
          color: block.cell.value.isEmpty
              ? theme.colorScheme.surfaceContainerHighest
              : color,
          borderRadius: BorderRadius.zero,
          border: Border.all(color: theme.colorScheme.outlineVariant),
        ),
        child: block.cell.value.isEmpty
            ? const SizedBox.shrink()
            : FittedBox(
                alignment: Alignment.topLeft,
                fit: BoxFit.scaleDown,
                child: ConstrainedBox(
                  constraints: const BoxConstraints(minWidth: 1, minHeight: 1),
                  child: Row(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: [
                          Row(
                            mainAxisSize: MainAxisSize.min,
                            children: [
                              if (block.cell.isPending)
                                Padding(
                                  padding: const EdgeInsets.only(right: 6),
                                  child: SizedBox(
                                    width: 16,
                                    height: 16,
                                    child: isPendingAction
                                        ? CircularProgressIndicator(
                                            strokeWidth: 2,
                                            valueColor:
                                                AlwaysStoppedAnimation(textColor),
                                          )
                                        : Icon(
                                            Icons.pending,
                                            size: 16,
                                            color: textColor,
                                          ),
                                  ),
                                ),
                              Text(
                                block.cell.value,
                                maxLines: 1,
                                overflow: TextOverflow.ellipsis,
                                style: theme.textTheme.bodyMedium?.copyWith(
                                      fontWeight: FontWeight.w700,
                                      color: textColor,
                                    ) ??
                                    TextStyle(
                                      fontWeight: FontWeight.w700,
                                      color: textColor,
                                    ),
                              ),
                            ],
                          ),
                          const SizedBox(height: 4),
                          Text(
                            block.cell.rangeLabel,
                            maxLines: 1,
                            overflow: TextOverflow.ellipsis,
                            style: theme.textTheme.labelSmall?.copyWith(
                                  color: textColor.withValues(alpha: 0.9),
                                ) ??
                                TextStyle(
                                  color: textColor.withValues(alpha: 0.9),
                                ),
                          ),
                        ],
                      ),
                    ],
                  ),
                ),
              ),
      ),
    );
  }
}

enum _TimelineBlockAction { edit, delete, approve, reject }

class _ValueBlockMenu extends StatelessWidget {
  const _ValueBlockMenu({
    required this.block,
    this.onEditEntry,
    this.onDeleteEntry,
    this.onModeratePending,
    this.pendingActionEventIds = const {},
  });

  final _ValueBlock block;
  final void Function(LocoAttrVersion entry)? onEditEntry;
  final void Function(LocoAttrVersion entry)? onDeleteEntry;
  final Future<void> Function(
    LocoAttrVersion entry,
    _PendingModerationAction action,
  )? onModeratePending;
  final Set<int> pendingActionEventIds;

  bool get _hasActions {
    final canModerate = block.entry?.isPending == true &&
        block.entry?.canModeratePending == true &&
        onModeratePending != null;
    final canEdit = onEditEntry != null && block.entry?.isPending != true;
    return onDeleteEntry != null || canModerate || canEdit;
  }

  @override
  Widget build(BuildContext context) {
    if (!_hasActions || block.entry == null) {
      return _ValueBlockView(
        block: block,
      );
    }
    final canModerate = block.entry?.isPending == true &&
        block.entry?.canModeratePending == true &&
        onModeratePending != null;
    final canEdit = onEditEntry != null && block.entry?.isPending != true;
    final eventId = block.entry?.sourceEventId;
    final isPendingAction =
        eventId != null && pendingActionEventIds.contains(eventId);

    Future<void> showContextMenuAt(Offset globalPosition) async {
      final overlay = Overlay.of(context);
      final renderBox = overlay.context.findRenderObject() as RenderBox?;
      if (renderBox == null) return;
      // Translate from global screen coordinates into the overlay's local space
      // so the menu appears where the gesture happened.
      final localPosition = renderBox.globalToLocal(globalPosition);
      final position = RelativeRect.fromRect(
        Rect.fromLTWH(localPosition.dx, localPosition.dy, 1, 1),
        Offset.zero & renderBox.size,
      );

      final action = await showMenu<_TimelineBlockAction>(
        context: context,
        position: position,
        items: [
          if (canEdit)
            const PopupMenuItem(
              value: _TimelineBlockAction.edit,
              child: Text('Edit'),
            ),
          if (canModerate)
            PopupMenuItem(
              value: _TimelineBlockAction.approve,
              enabled: !isPendingAction,
              child: const Text('Approve pending'),
            ),
          if (canModerate)
            PopupMenuItem(
              value: _TimelineBlockAction.reject,
              enabled: !isPendingAction,
              child: const Text('Reject pending'),
            ),
          if (onDeleteEntry != null)
            const PopupMenuItem(
              value: _TimelineBlockAction.delete,
              child: Text('Delete'),
            ),
        ],
      );

      final entry = block.entry;
      if (action == null || entry == null) return;
      switch (action) {
        case _TimelineBlockAction.edit:
          onEditEntry?.call(entry);
          break;
        case _TimelineBlockAction.delete:
          onDeleteEntry?.call(entry);
          break;
        case _TimelineBlockAction.approve:
          onModeratePending?.call(entry, _PendingModerationAction.approve);
          break;
        case _TimelineBlockAction.reject:
          onModeratePending?.call(entry, _PendingModerationAction.reject);
          break;
      }
    }

    return GestureDetector(
      behavior: HitTestBehavior.deferToChild,
      onLongPressStart: (details) async {
        if (defaultTargetPlatform == TargetPlatform.android) {
          HapticFeedback.lightImpact();
        }
        await showContextMenuAt(details.globalPosition);
      },
      onSecondaryTapDown: (details) async {
        await showContextMenuAt(details.globalPosition);
      },
      child: _ValueBlockView(
        block: block,
        pendingActionEventIds: pendingActionEventIds,
      ),
    );
  }
}

String? _formatDate(DateTime? date) {
  if (date == null) return null;
  return _dateFormat.format(date);
}

String _formatAttrLabel(String code) {
  if (code.isEmpty) return 'Attribute';
  final parts = code.split('_').where((p) => p.isNotEmpty).toList();
  if (parts.isEmpty) return code;
  return parts
      .map((part) => part.length == 1
          ? part.toUpperCase()
          : part[0].toUpperCase() + part.substring(1))
      .join(' ');
}

DateTime? _parseDateString(String? value) {
  if (value == null || value.isEmpty) return null;
  final direct = DateTime.tryParse(value);
  if (direct != null) return direct;
  final maskedMatch =
      RegExp(r'^(\\d{4})-(\\d{2}|xx|XX)-(\\d{2}|xx|XX)\$').firstMatch(value);
  if (maskedMatch != null) {
    final year = int.tryParse(maskedMatch.group(1) ?? '');
    if (year == null) return null;
    String normalize(String part, int fallback) {
      final lower = part.toLowerCase();
      if (lower == 'xx') return fallback.toString().padLeft(2, '0');
      return part;
    }

    final month = int.tryParse(normalize(maskedMatch.group(2) ?? '01', 1)) ?? 1;
    final day = int.tryParse(normalize(maskedMatch.group(3) ?? '01', 1)) ?? 1;
    try {
      return DateTime(year, month.clamp(1, 12), day.clamp(1, 31));
    } catch (_) {
      return null;
    }
  }
  return null;
}

DateTime? _effectiveStart(LocoAttrVersion entry) {
  return entry.validFrom ??
      _parseDateString(entry.maskedValidFrom) ??
      entry.txnFrom;
}

DateTime _safeEnd(DateTime start, DateTime? end) {
  if (end == null || !end.isAfter(start)) {
    return start.add(const Duration(days: 1));
  }
  return end;
}

int _startKey(DateTime date) => date.year * 10000 + date.month * 100 + date.day;

bool _isOverlappingStart(LocoAttrVersion entry, Set<int> approvedStartKeys) {
  final start = _effectiveStart(entry);
  if (start == null) return false;
  return approvedStartKeys.contains(_startKey(start));
}

List<_ValueSegment> _segmentsForEntries(
  List<LocoAttrVersion> items,
  DateTime now, {
  bool? clampToNextStart,
}) {
  if (items.isEmpty) return const [];
  final hasPending = items.any((e) => e.isPending);
  final hasApproved = items.any((e) => !e.isPending);
  final shouldClamp =
      clampToNextStart ?? (hasPending && hasApproved);
  final sorted = [...items];
  sorted.sort(
    (a, b) => (_effectiveStart(a) ?? now)
        .compareTo(_effectiveStart(b) ?? now),
  );
  final segments = <_ValueSegment>[];
  for (int i = 0; i < sorted.length; i++) {
    final entry = sorted[i];
    final start = _effectiveStart(entry) ?? now;
    final nextStart = i < sorted.length - 1
        ? _effectiveStart(sorted[i + 1])
        : null;
    DateTime? rawEnd = entry.validTo;
    if (nextStart != null) {
      if (rawEnd == null || (shouldClamp && nextStart.isBefore(rawEnd))) {
        rawEnd = nextStart;
      }
    }
    rawEnd ??= now;
    final end = _safeEnd(start, rawEnd);
    segments.add(
      _ValueSegment(
        start: start,
        end: end,
        value: _formatValueWithUnits(entry),
        entry: entry,
      ),
    );
  }
  return segments;
}

List<LocoAttrVersion> _applyPendingOverrides(
  List<LocoAttrVersion> approved,
  List<LocoAttrVersion> pending,
) {
  if (pending.isEmpty) return approved;
  final pendingByStart = <int, LocoAttrVersion>{};
  final extraPending = <LocoAttrVersion>[];
  for (final entry in pending) {
    final start = _effectiveStart(entry);
    if (start == null) continue;
    final key = _startKey(start);
    pendingByStart[key] = entry;
  }

  final applied = <LocoAttrVersion>[];
  final seenKeys = <int>{};
  for (final entry in approved) {
    final start = _effectiveStart(entry);
    if (start == null) continue;
    final key = _startKey(start);
    if (pendingByStart.containsKey(key)) {
      if (!seenKeys.contains(key)) {
        applied.add(pendingByStart[key]!);
        seenKeys.add(key);
      }
    } else {
      applied.add(entry);
      seenKeys.add(key);
    }
  }

  for (final entry in pendingByStart.values) {
    final start = _effectiveStart(entry);
    if (start == null) continue;
    final key = _startKey(start);
    if (!seenKeys.contains(key)) {
      extraPending.add(entry);
      seenKeys.add(key);
    }
  }

  if (extraPending.isNotEmpty) {
    applied.addAll(extraPending);
  }
  return applied;
}

List<DateTime> _buildBoundaries(
  List<_ValueSegment> segments,
  DateTime now,
) {
  DateTime? minStart;
  DateTime? maxEnd;
  final boundaryDates = <DateTime>{};
  for (final seg in segments) {
    boundaryDates.add(seg.start);
    boundaryDates.add(seg.end);
    minStart = minStart == null || seg.start.isBefore(minStart!)
        ? seg.start
        : minStart;
    maxEnd = maxEnd == null || seg.end.isAfter(maxEnd!) ? seg.end : maxEnd;
  }
  minStart ??= now.subtract(const Duration(days: 1));
  final effectiveMaxEnd = maxEnd ?? now;
  boundaryDates.add(effectiveMaxEnd);
  var boundaries = boundaryDates.toList()..sort();
  if (boundaries.length < 2) {
    boundaries = [minStart!, effectiveMaxEnd];
  }
  return boundaries;
}

class _TimelineRowSpec {
  final String id;
  final String attrCode;
  final List<_ValueSegment> segments;
  final bool isPrimary;
  final bool showExpandToggle;
  final bool isExpanded;
  final String? userLabel;

  const _TimelineRowSpec._({
    required this.id,
    required this.attrCode,
    required this.segments,
    required this.isPrimary,
    required this.showExpandToggle,
    required this.isExpanded,
    this.userLabel,
  });

  factory _TimelineRowSpec.primary({
    required String attrCode,
    required List<_ValueSegment> segments,
    required bool showExpandToggle,
    required bool isExpanded,
  }) {
    return _TimelineRowSpec._(
      id: attrCode,
      attrCode: attrCode,
      segments: segments,
      isPrimary: true,
      showExpandToggle: showExpandToggle,
      isExpanded: isExpanded,
    );
  }

  factory _TimelineRowSpec.pending({
    required String attrCode,
    required String userLabel,
    required List<_ValueSegment> segments,
  }) {
    return _TimelineRowSpec._(
      id: '$attrCode::$userLabel',
      attrCode: attrCode,
      segments: segments,
      isPrimary: false,
      showExpandToggle: false,
      isExpanded: false,
      userLabel: userLabel,
    );
  }
}

class _TimelineRowData {
  final String id;
  final String attrCode;
  final List<_ValueBlock> blocks;
  final bool isPrimary;
  final bool showExpandToggle;
  final bool isExpanded;
  final String? pendingUser;

  const _TimelineRowData({
    required this.id,
    required this.attrCode,
    required this.blocks,
    required this.isPrimary,
    required this.showExpandToggle,
    required this.isExpanded,
    this.pendingUser,
  });
}

class _TimelineModel {
  final List<_AxisSegment> axisSegments;
  final List<_TimelineRowData> rows;
  final String endLabel;
  final List<DateTime> boundaries;
  final double axisTotalWidth;

  _TimelineModel({
    required this.axisSegments,
    required this.rows,
    required this.endLabel,
    required this.boundaries,
    required this.axisTotalWidth,
  });

  factory _TimelineModel.fromEntries(
    List<LocoAttrVersion> entries, {
    Set<String> expandedAttrCodes = const {},
  }) {
    final effectiveEntries = entries
        .where((e) => _effectiveStart(e) != null)
        .toList();
    final grouped = <String, List<LocoAttrVersion>>{};
    final attrOrder = <String>[];
    for (final entry in effectiveEntries) {
      final key = entry.attrCode;
      if (!grouped.containsKey(key)) {
        attrOrder.add(key);
      }
      grouped.putIfAbsent(key, () => []).add(entry);
    }
    final now = DateTime.now();
    final allSegments = <_ValueSegment>[];
    final rowSpecs = <_TimelineRowSpec>[];
    for (final attr in attrOrder) {
      final items = grouped[attr] ?? const [];
      final approved = items.where((e) => !e.isPending).toList();
      final pending = items.where((e) => e.isPending).toList();
      final approvedSegments = _segmentsForEntries(approved, now);

      final approvedStartKeys = <int>{};
      for (final entry in approved) {
        final start = _effectiveStart(entry);
        if (start == null) continue;
        approvedStartKeys.add(_startKey(start));
      }

      final pendingByUser = <String, List<LocoAttrVersion>>{};
      final overlapByUser = <String, List<LocoAttrVersion>>{};
      for (final entry in pending) {
        final user = (entry.suggestedBy ?? '').trim().isEmpty
            ? 'Unknown'
            : entry.suggestedBy!.trim();
        pendingByUser.putIfAbsent(user, () => []).add(entry);
        final start = _effectiveStart(entry);
        if (start == null) continue;
        if (approvedStartKeys.contains(_startKey(start))) {
          overlapByUser.putIfAbsent(user, () => []).add(entry);
        }
      }

      final hasOverlap = overlapByUser.isNotEmpty;
      final canToggle = pending.isNotEmpty && !hasOverlap;
      final isExpanded = expandedAttrCodes.contains(attr);
      final shouldShowPendingRows = isExpanded || hasOverlap;

      final nonOverlapPending =
          pending.where((e) => !_isOverlappingStart(e, approvedStartKeys)).toList();
      final baseEntries =
          shouldShowPendingRows ? approved : [...approved, ...nonOverlapPending];
      final baseSegments = shouldShowPendingRows
          ? approvedSegments
          : _segmentsForEntries(baseEntries, now);

      rowSpecs.add(
        _TimelineRowSpec.primary(
          attrCode: attr,
          segments: baseSegments,
          showExpandToggle: canToggle,
          isExpanded: isExpanded,
        ),
      );
      allSegments.addAll(baseSegments);

      if (shouldShowPendingRows) {
        final users = isExpanded
            ? pendingByUser.keys.toList()
            : overlapByUser.keys.toList();
        users.sort();
        for (final user in users) {
          final pendingEntries = isExpanded
              ? (pendingByUser[user] ?? const [])
              : (overlapByUser[user] ?? const []);
          if (pendingEntries.isEmpty) continue;
          final appliedEntries =
              _applyPendingOverrides(approved, pendingEntries);
          final combinedSegments = _segmentsForEntries(appliedEntries, now);
          rowSpecs.add(
            _TimelineRowSpec.pending(
              attrCode: attr,
              userLabel: user,
              segments: combinedSegments,
            ),
          );
          allSegments.addAll(combinedSegments);
        }
      }
    }

    final boundaries = _buildBoundaries(allSegments, now);

    final axisSegments = <_AxisSegment>[];
    const double yearWidth = 240.0;
    for (int i = 0; i < boundaries.length - 1; i++) {
      final start = boundaries[i];
      final end = boundaries[i + 1];
      const width = yearWidth;
      final double offset = axisSegments.isEmpty
          ? 0.0
          : axisSegments.last.offset + axisSegments.last.width;
      axisSegments.add(
        _AxisSegment(
          start: start,
          end: end,
          width: width,
          offset: offset,
          label: _formatDate(start) ?? '',
        ),
      );
    }
    final axisTotalWidth =
        axisSegments.fold<double>(0, (sum, seg) => sum + seg.width);

    final rows = <_TimelineRowData>[];
    for (final spec in rowSpecs) {
      final blocks = <_ValueBlock>[];
      for (final seg in spec.segments) {
        final left = _positionForDate(seg.start, boundaries, axisSegments);
        final right = _positionForDate(seg.end, boundaries, axisSegments);
        final span = right - left;
        final width = span < 2.0 ? 2.0 : span;
        blocks.add(
          _ValueBlock(
            left: left,
            width: width,
            cell: _RowCell.fromSegment(seg),
            entry: seg.entry,
          ),
        );
      }
      rows.add(
        _TimelineRowData(
          id: spec.id,
          attrCode: spec.attrCode,
          blocks: blocks,
          isPrimary: spec.isPrimary,
          showExpandToggle: spec.showExpandToggle,
          isExpanded: spec.isExpanded,
          pendingUser: spec.userLabel,
        ),
      );
    }

    final endLabel =
        boundaries.isNotEmpty ? _formatDate(boundaries.last) ?? 'Now' : 'Now';
    return _TimelineModel(
      axisSegments: axisSegments,
      rows: rows,
      endLabel: endLabel,
      boundaries: boundaries,
      axisTotalWidth: axisTotalWidth,
    );
  }

  static double _positionForDate(
    DateTime date,
    List<DateTime> boundaries,
    List<_AxisSegment> segments,
  ) {
    for (int i = 0; i < boundaries.length - 1; i++) {
      final start = boundaries[i];
      final end = boundaries[i + 1];
      if (!date.isAfter(end)) {
        final seg = segments[i];
        final span = end.difference(start).inMilliseconds;
        final elapsed = date.difference(start).inMilliseconds.clamp(0, span);
        if (span <= 0) return seg.offset;
        final fraction = elapsed / span;
        return seg.offset + (seg.width * fraction);
      }
    }
    return segments.isNotEmpty
        ? segments.last.offset + segments.last.width
        : 0.0;
  }
}

String _formatValueWithUnits(LocoAttrVersion entry) {
  final raw = entry.valueLabel;
  final code = entry.attrCode.toLowerCase();
  final lowerRaw = raw.toLowerCase();
  // Avoid double-appending if units already present.
  final hasUnits = lowerRaw.contains('mm') ||
      lowerRaw.contains('tonne') ||
      lowerRaw.contains('kph') ||
      lowerRaw.contains('mph');

  double? asNumber = double.tryParse(raw);
  String formatNumber(double value) {
    if (value % 1 == 0) return value.toStringAsFixed(0);
    return value.toStringAsFixed(2);
  }

  switch (code) {
    case 'height':
    case 'length':
    case 'width':
    case 'track_gauge':
      if (hasUnits) return raw;
      return asNumber != null ? '${formatNumber(asNumber)} mm' : '$raw mm';
    case 'weight':
      if (hasUnits) return raw;
      return asNumber != null ? '${formatNumber(asNumber)} tonnes' : '$raw tonnes';
    case 'power':
      if (hasUnits) return raw;
      return asNumber != null ? '${formatNumber(asNumber)} kW' : '$raw kW';
    case 'tractive_effort':
      if (hasUnits) return raw;
      return asNumber != null ? '${formatNumber(asNumber)} kN' : '$raw kN';
    case 'max_speed':
      if (hasUnits) return raw;
      if (asNumber != null) {
        // Stored as kph.
        final formatted = asNumber % 1 == 0
            ? asNumber.toStringAsFixed(0)
            : asNumber.toStringAsFixed(1);
        return '$formatted kph';
      }
      return '$raw kph';
    default:
      return raw;
  }
}

class _AxisSegment {
  final DateTime start;
  final DateTime end;
  final double width;
  final double offset;
  final String label;

  _AxisSegment({
    required this.start,
    required this.end,
    required this.width,
    required this.offset,
    required this.label,
  });
}

class _ValueSegment {
  final DateTime start;
  final DateTime end;
  final String value;
  final LocoAttrVersion? entry;

  _ValueSegment({
    required this.start,
    required this.end,
    required this.value,
    this.entry,
  });

  bool overlaps(DateTime s, DateTime e) {
    return start.isBefore(e) && end.isAfter(s);
  }

  _ValueSegment copyWith({DateTime? start, DateTime? end, String? value}) {
    return _ValueSegment(
      start: start ?? this.start,
      end: end ?? this.end,
      value: value ?? this.value,
      entry: entry,
    );
  }
}

class _RowCell {
  final String value;
  final String rangeLabel;
  final Color color;
  final bool isPending;

  const _RowCell({
    required this.value,
    required this.rangeLabel,
    required this.color,
    this.isPending = false,
  });

  factory _RowCell.fromSegment(_ValueSegment seg) {
    if (seg.value.isEmpty) {
      return const _RowCell(
        value: '',
        rangeLabel: '',
        color: Colors.transparent,
        isPending: false,
      );
    }
    final entry = seg.entry;
    String displayStart = '';
    if (entry != null) {
      if ((entry.maskedValidFrom ?? '').trim().isNotEmpty) {
        displayStart = entry.maskedValidFrom!.trim();
      } else if (entry.validFrom != null) {
        displayStart = _formatDate(entry.validFrom) ?? '';
      }
    }
    return _RowCell(
      value: seg.value,
      rangeLabel: displayStart,
      color: _colorForValue(seg.value),
      isPending: entry?.isPending ?? false,
    );
  }
}

class _ValueBlock {
  final double left;
  final double width;
  final _RowCell cell;
  final LocoAttrVersion? entry;

  const _ValueBlock({
    required this.left,
    required this.width,
    required this.cell,
    required this.entry,
  });

  double get right => left + width;

  _ValueBlock copyWith({
    double? left,
    double? width,
    _RowCell? cell,
    LocoAttrVersion? entry,
  }) {
    return _ValueBlock(
      left: left ?? this.left,
      width: width ?? this.width,
      cell: cell ?? this.cell,
      entry: entry ?? this.entry,
    );
  }
}

Color _colorForValue(String value) {
  final hue = (value.hashCode % 360).toDouble();
  final hsl = HSLColor.fromAHSL(1, hue, 0.55, 0.55);
  return hsl.toColor();
}