import 'dart:async';

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

import '../diagnostics/badnote_log.dart';
import '../editor/board/board.dart';
import '../l10n/app_localizations.dart';
import '../services/database_service.dart';
import '../theme/app_theme.dart';

const _kDefaultBoardId = 'main';

/// Infinite sticky-note board — first-class shell destination (F7).
class BoardScreen extends ConsumerStatefulWidget {
  const BoardScreen({super.key});

  @override
  ConsumerState<BoardScreen> createState() => _BoardScreenState();
}

class _BoardScreenState extends ConsumerState<BoardScreen> {
  Board _board = Board.empty;
  bool _loading = true;
  String? _selectedId;
  final _transform = TransformationController();
  Timer? _saveDebounce;

  @override
  void initState() {
    super.initState();
    _load();
  }

  @override
  void dispose() {
    _saveDebounce?.cancel();
    _transform.dispose();
    super.dispose();
  }

  Future<void> _load() async {
    final db = await DatabaseService.getInstance();
    final board = await db.loadBoard(_kDefaultBoardId);
    if (!mounted) return;
    setState(() {
      _board = board;
      _loading = false;
    });
    BadNoteLog.instance.info(
      LogSubsystem.board,
      'board_loaded',
      fields: {'cards': board.length},
    );
  }

  void _scheduleSave() {
    _saveDebounce?.cancel();
    _saveDebounce = Timer(const Duration(milliseconds: 400), () async {
      final db = await DatabaseService.getInstance();
      await db.saveBoardCards(_kDefaultBoardId, _board.cards);
      BadNoteLog.instance.debug(
        LogSubsystem.board,
        'board_saved',
        fields: {'cards': _board.length},
      );
    });
  }

  void _addCard() {
    final l = AppLocalizations.of(context);
    final id = const Uuid().v4();
    // Place near viewport center in scene coords.
    final matrix = _transform.value;
    final inv = Matrix4.inverted(matrix);
    final center = MatrixUtils.transformPoint(
      inv,
      Offset(
        MediaQuery.sizeOf(context).width / 2,
        MediaQuery.sizeOf(context).height / 2,
      ),
    );
    setState(() {
      _board = _board.add(
        BoardCard(
          id: id,
          position: center - const Offset(120, 80),
          size: const Size(240, 160),
          text: l.boardNewCardText,
        ),
      );
      _selectedId = id;
    });
    _scheduleSave();
  }

  void _deleteSelected() {
    final id = _selectedId;
    if (id == null) return;
    final l = AppLocalizations.of(context);
    showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: Text(l.boardDeleteCardTitle),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx, false),
            child: Text(l.cancel),
          ),
          TextButton(
            onPressed: () => Navigator.pop(ctx, true),
            child: Text(l.boardDeleteCard),
          ),
        ],
      ),
    ).then((ok) {
      if (ok != true) return;
      setState(() {
        _board = _board.removeById(id);
        _selectedId = null;
      });
      _scheduleSave();
    });
  }

  @override
  Widget build(BuildContext context) {
    final l = AppLocalizations.of(context);
    if (_loading) {
      return const Center(child: CircularProgressIndicator());
    }

    final selected = _selectedId != null ? _board.cardById(_selectedId!) : null;
    final backlinks =
        selected != null ? _board.backlinksOf(selected.id) : <String>{};

    return Scaffold(
      backgroundColor: Theme.of(context).colorScheme.surface,
      appBar: AppBar(
        title: Text(l.boardTitle),
        actions: [
          IconButton(
            tooltip: l.boardAddCard,
            onPressed: _addCard,
            icon: const Icon(Icons.add),
          ),
          if (_selectedId != null)
            IconButton(
              tooltip: l.boardDeleteCard,
              onPressed: _deleteSelected,
              icon: const Icon(Icons.delete_outline),
            ),
        ],
      ),
      body: Row(
        children: [
          Expanded(
            child: InteractiveViewer(
              transformationController: _transform,
              constrained: false,
              boundaryMargin: const EdgeInsets.all(2000),
              minScale: 0.25,
              maxScale: 3,
              child: SizedBox(
                width: 4000,
                height: 3000,
                child: CustomPaint(
                  painter: _BoardGridPainter(
                    color: AppTokens.rule.withValues(alpha: 0.45),
                  ),
                  child: Stack(
                    children: [
                      for (final card in _board.cards)
                        Positioned(
                          left: card.position.dx,
                          top: card.position.dy,
                          width: card.size.width,
                          height: card.size.height,
                          child: _StickyCard(
                            card: card,
                            selected: card.id == _selectedId,
                            onTap: () => setState(() => _selectedId = card.id),
                            onDrag: (delta) {
                              setState(() {
                                _board = _board.moveCard(
                                  card.id,
                                  card.position + delta,
                                );
                              });
                              _scheduleSave();
                            },
                            onTextChanged: (text) {
                              setState(() {
                                _board = _board.setText(card.id, text);
                              });
                              _scheduleSave();
                            },
                          ),
                        ),
                    ],
                  ),
                ),
              ),
            ),
          ),
          if (selected != null)
            SizedBox(
              width: 260,
              child: Material(
                elevation: 1,
                color: Theme.of(context).colorScheme.surface,
                child: Padding(
                  padding: const EdgeInsets.all(AppTokens.chromePad),
                  child: Column(
                    crossAxisAlignment: CrossAxisAlignment.start,
                    children: [
                      Text(
                        l.boardBacklinks,
                        style: Theme.of(context).textTheme.titleSmall,
                      ),
                      const SizedBox(height: 8),
                      if (backlinks.isEmpty)
                        Text(
                          l.boardNoBacklinks,
                          style: Theme.of(context).textTheme.bodySmall,
                        )
                      else
                        ...backlinks.map((id) {
                          final c = _board.cardById(id);
                          return ListTile(
                            dense: true,
                            contentPadding: EdgeInsets.zero,
                            title: Text(c?.text.split('\n').first ?? id),
                            onTap: () => setState(() => _selectedId = id),
                          );
                        }),
                      const Divider(),
                      Text(
                        '[[links]]',
                        style: Theme.of(context).textTheme.labelMedium,
                      ),
                      const SizedBox(height: 4),
                      Text(
                        '在便利贴正文里写 [[另一张卡片id]] 建立双链',
                        style: Theme.of(context).textTheme.bodySmall?.copyWith(
                              color: AppTokens.inkMuted,
                            ),
                      ),
                    ],
                  ),
                ),
              ),
            ),
        ],
      ),
      floatingActionButton: FloatingActionButton.extended(
        onPressed: _addCard,
        icon: const Icon(Icons.sticky_note_2),
        label: Text(l.boardAddCard),
      ),
    );
  }
}

class _StickyCard extends StatefulWidget {
  const _StickyCard({
    required this.card,
    required this.selected,
    required this.onTap,
    required this.onDrag,
    required this.onTextChanged,
  });

  final BoardCard card;
  final bool selected;
  final VoidCallback onTap;
  final ValueChanged<Offset> onDrag;
  final ValueChanged<String> onTextChanged;

  @override
  State<_StickyCard> createState() => _StickyCardState();
}

class _StickyCardState extends State<_StickyCard> {
  late final TextEditingController _controller =
      TextEditingController(text: widget.card.text);

  @override
  void didUpdateWidget(covariant _StickyCard oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.card.text != widget.card.text &&
        _controller.text != widget.card.text) {
      _controller.text = widget.card.text;
    }
  }

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

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: widget.onTap,
      onPanUpdate: (d) => widget.onDrag(d.delta),
      child: AnimatedContainer(
        duration: const Duration(milliseconds: 120),
        padding: const EdgeInsets.all(10),
        decoration: BoxDecoration(
          color: AppTokens.sticky,
          borderRadius: BorderRadius.circular(AppTokens.radiusSm),
          border: Border.all(
            color: widget.selected ? AppTokens.copper : AppTokens.rule,
            width: widget.selected ? 2 : 1,
          ),
          boxShadow: [
            BoxShadow(
              color: Colors.black.withValues(alpha: 0.08),
              blurRadius: 8,
              offset: const Offset(0, 3),
            ),
          ],
        ),
        child: TextField(
          controller: _controller,
          maxLines: null,
          style: Theme.of(context).textTheme.bodyMedium?.copyWith(
                color: AppTokens.ink,
              ),
          decoration: const InputDecoration(
            border: InputBorder.none,
            isDense: true,
            contentPadding: EdgeInsets.zero,
          ),
          onChanged: widget.onTextChanged,
        ),
      ),
    );
  }
}

class _BoardGridPainter extends CustomPainter {
  _BoardGridPainter({required this.color});
  final Color color;

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = color
      ..strokeWidth = 1;
    const step = 48.0;
    for (double x = 0; x < size.width; x += step) {
      canvas.drawLine(Offset(x, 0), Offset(x, size.height), paint);
    }
    for (double y = 0; y < size.height; y += step) {
      canvas.drawLine(Offset(0, y), Offset(size.width, y), paint);
    }
  }

  @override
  bool shouldRepaint(covariant _BoardGridPainter oldDelegate) =>
      oldDelegate.color != color;
}