import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

import '../engine/brush.dart';

/// OneNote-style independent pen slot: brush + color + thickness together.
///
/// Selecting a slot restores all three; color dots / thickness controls edit
/// only the active slot.
class PenSlot {
  const PenSlot({
    required this.id,
    required this.brush,
    required this.color,
    required this.width,
  });

  final String id;

  /// Brush kind for this slot (fountain / ballpoint / pencil — not highlighter).
  final BrushKind brush;

  final Color color;

  /// Stroke width as a fraction of page width.
  final double width;

  PenSlot copyWith({
    String? id,
    BrushKind? brush,
    Color? color,
    double? width,
  }) {
    return PenSlot(
      id: id ?? this.id,
      brush: brush ?? this.brush,
      color: color ?? this.color,
      width: width ?? this.width,
    );
  }

  Map<String, dynamic> toJson() => {
        'id': id,
        'brush': brush.name,
        'color': color.toARGB32(),
        'width': width,
      };

  factory PenSlot.fromJson(Map<String, dynamic> json) {
    final brushName = json['brush'] as String? ?? '';
    return PenSlot(
      id: json['id'] as String? ?? 'slot_0',
      brush: BrushKind.values.asNameMap()[brushName] ?? BrushKind.fountainPen,
      color: Color(json['color'] as int? ?? 0xFF000000),
      width: (json['width'] as num?)?.toDouble() ?? 0.006,
    );
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
      other is PenSlot &&
          runtimeType == other.runtimeType &&
          id == other.id &&
          brush == other.brush &&
          color.toARGB32() == other.color.toARGB32() &&
          width == other.width;

  @override
  int get hashCode => Object.hash(id, brush, color.toARGB32(), width);
}

/// Default pen slots seeded OneNote-style (fountain / ballpoint / pencil).
List<PenSlot> kDefaultPenSlots() => const [
      PenSlot(
        id: 'slot_0',
        brush: BrushKind.fountainPen,
        color: Colors.black,
        width: 0.006,
      ),
      PenSlot(
        id: 'slot_1',
        brush: BrushKind.ballpoint,
        color: Colors.blue,
        width: 0.0022,
      ),
      PenSlot(
        id: 'slot_2',
        brush: BrushKind.pencil,
        color: Colors.green,
        width: 0.003,
      ),
    ];

/// S / M / L thickness presets (page-width fractions) for the toolbar picker.
const double kThicknessSmall = 0.0022;
const double kThicknessMedium = 0.006;
const double kThicknessLarge = 0.012;

/// Allowed range for slot stroke width (page-width fraction).
const double kPenSlotWidthMin = 0.001;
const double kPenSlotWidthMax = 0.05;

/// Manages independent [PenSlot]s with SharedPreferences persistence.
///
/// Load with [PenSlotsController.load], then listen via [ChangeNotifier].
class PenSlotsController extends ChangeNotifier {
  PenSlotsController._(this._prefs, this._slots, this._activeId);

  /// SharedPreferences key for the slots JSON blob.
  static const prefsKey = 'pen_slots_v1';

  final SharedPreferences _prefs;
  List<PenSlot> _slots;
  String _activeId;

  List<PenSlot> get slots => List.unmodifiable(_slots);

  String get activeId => _activeId;

  PenSlot get active {
    for (final s in _slots) {
      if (s.id == _activeId) return s;
    }
    return _slots.first;
  }

  /// Loads persisted slots, or seeds [kDefaultPenSlots] on first run / corrupt
  /// JSON.
  static Future<PenSlotsController> load() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(prefsKey);
    var slots = kDefaultPenSlots();
    var activeId = slots.first.id;
    if (raw != null) {
      try {
        final map = jsonDecode(raw) as Map<String, dynamic>;
        final list = map['slots'] as List<dynamic>?;
        if (list != null && list.isNotEmpty) {
          slots = [
            for (final e in list)
              PenSlot.fromJson(e as Map<String, dynamic>),
          ];
        }
        final storedActive = map['activeId'] as String?;
        if (storedActive != null &&
            slots.any((s) => s.id == storedActive)) {
          activeId = storedActive;
        } else {
          activeId = slots.first.id;
        }
      } catch (_) {
        slots = kDefaultPenSlots();
        activeId = slots.first.id;
      }
    }
    return PenSlotsController._(prefs, slots, activeId);
  }

  Future<void> _persist() async {
    await _prefs.setString(
      prefsKey,
      jsonEncode({
        'activeId': _activeId,
        'slots': [for (final s in _slots) s.toJson()],
      }),
    );
  }

  int _indexOfActive() {
    final i = _slots.indexWhere((s) => s.id == _activeId);
    return i >= 0 ? i : 0;
  }

  void _replaceActive(PenSlot next) {
    final i = _indexOfActive();
    _slots = [..._slots]..[i] = next;
  }

  /// Selects [id] as the active slot (restores brush + color + width).
  Future<void> select(String id) async {
    if (!_slots.any((s) => s.id == id)) return;
    if (_activeId == id) return;
    _activeId = id;
    notifyListeners();
    await _persist();
  }

  /// Sets the active slot's color.
  Future<void> setActiveColor(Color c) async {
    _replaceActive(active.copyWith(color: c));
    notifyListeners();
    await _persist();
  }

  /// Sets the active slot's stroke width (clamped).
  Future<void> setActiveWidth(double w) async {
    final clamped = w.clamp(kPenSlotWidthMin, kPenSlotWidthMax);
    _replaceActive(active.copyWith(width: clamped));
    notifyListeners();
    await _persist();
  }

  /// Sets the active slot's brush kind.
  Future<void> setActiveBrush(BrushKind b) async {
    if (b == BrushKind.highlighter) return;
    _replaceActive(active.copyWith(brush: b));
    notifyListeners();
    await _persist();
  }
}