import 'dart:convert';
import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart' show Color;
import 'package:path/path.dart' as p;
import 'package:path_provider/path_provider.dart';

/// One belt level with its ITF grading requirements.
class BeltLevel {
  const BeltLevel({
    required this.id,
    required this.gup,
    required this.name,
    required this.baseColor,
    this.stripeColor,
    required this.requirements,
  });

  final String id;
  final String gup;
  final String name;
  final Color baseColor;
  final Color? stripeColor;
  final List<String> requirements;
}

/// Tracks grading preparation: which requirements are checked off per belt,
/// and which belt the user is currently preparing for. Persisted as JSON.
class GradingService extends ChangeNotifier {
  static const _fileName = 'trainhub_grading.json';

  String? _currentBeltId;
  Map<String, Set<int>> _checked = {};
  bool _loaded = false;

  String? get currentBeltId => _currentBeltId;

  bool isChecked(String beltId, int index) =>
      _checked[beltId]?.contains(index) ?? false;

  int checkedCount(String beltId) => _checked[beltId]?.length ?? 0;

  double progress(BeltLevel belt) => belt.requirements.isEmpty
      ? 0
      : checkedCount(belt.id) / belt.requirements.length;

  Future<File> _file() async {
    final dir = await getApplicationDocumentsDirectory();
    return File(p.join(dir.path, _fileName));
  }

  Future<void> ensureLoaded() async {
    if (_loaded) return;
    _loaded = true;
    try {
      final file = await _file();
      if (!file.existsSync()) return;
      final json = jsonDecode(await file.readAsString());
      _currentBeltId = json['current'] as String?;
      _checked = {
        for (final entry in (json['checked'] as Map? ?? {}).entries)
          entry.key as String: {
            for (final i in entry.value as List) (i as num).toInt(),
          },
      };
      notifyListeners();
    } catch (e) {
      if (kDebugMode) debugPrint('Failed to load grading state: $e');
    }
  }

  void toggle(String beltId, int index) {
    final set = _checked.putIfAbsent(beltId, () => {});
    set.contains(index) ? set.remove(index) : set.add(index);
    notifyListeners();
    _persist();
  }

  void setCurrentBelt(String? beltId) {
    _currentBeltId = beltId;
    notifyListeners();
    _persist();
  }

  Future<void> _persist() async {
    try {
      final file = await _file();
      await file.writeAsString(
        jsonEncode({
          'current': _currentBeltId,
          'checked': {
            for (final entry in _checked.entries)
              entry.key: entry.value.toList(),
          },
        }),
      );
    } catch (e) {
      if (kDebugMode) debugPrint('Failed to save grading state: $e');
    }
  }
}

// ---------------------------------------------------------------------------
// ITF colored-belt syllabus (10 gup → 1 gup)
// ---------------------------------------------------------------------------

const _white = Color(0xFFF4F4F5);
const _yellow = Color(0xFFFACC15);
const _green = Color(0xFF22C55E);
const _blue = Color(0xFF3B82F6);
const _red = Color(0xFFFF2B2B);
const _black = Color(0xFF18181B);

const kBeltSyllabus = <BeltLevel>[
  BeltLevel(
    id: '10gup',
    gup: '10 GUP',
    name: 'White → Yellow Stripe',
    baseColor: _white,
    stripeColor: _yellow,
    requirements: [
      'Saju Jirugi (4-direction punch)',
      'Saju Makgi (4-direction block)',
      'Stances: charyot, narani, annun, gunnun sogi',
      'Ap Chagi (front snap kick) — both legs',
      'Theory: meaning of Taekwon-Do, belt colors, dojang etiquette',
    ],
  ),
  BeltLevel(
    id: '9gup',
    gup: '9 GUP',
    name: 'Yellow Stripe → Yellow',
    baseColor: _white,
    stripeColor: _yellow,
    requirements: [
      'Tul: Chon-Ji (19 movements)',
      'Niunja sogi (L-stance) + palmok daebi makgi',
      'Ap Chagi and Yop Chagi from walking stance',
      '3-step sparring (Sambo Matsogi) #1–2',
      'Theory: meaning of Chon-Ji, counting in Korean 1–10',
    ],
  ),
  BeltLevel(
    id: '8gup',
    gup: '8 GUP',
    name: 'Yellow',
    baseColor: _yellow,
    requirements: [
      'Tul: Dan-Gun (21 movements)',
      'Sonkal daebi makgi (knife-hand guarding block)',
      'Dollyo Chagi (turning kick) — both legs',
      '3-step sparring #1–4',
      'Theory: meaning of Dan-Gun, yellow belt symbolism',
    ],
  ),
  BeltLevel(
    id: '7gup',
    gup: '7 GUP',
    name: 'Yellow → Green Stripe',
    baseColor: _yellow,
    stripeColor: _green,
    requirements: [
      'Tul: Do-San (24 movements)',
      'Bakat palmok makgi + sonkal taerigi combinations',
      'Yopcha Jirugi (side piercing kick) — height improvement',
      '3-step sparring full set',
      'Theory: meaning of Do-San (Ahn Chang-Ho)',
    ],
  ),
  BeltLevel(
    id: '6gup',
    gup: '6 GUP',
    name: 'Green',
    baseColor: _green,
    requirements: [
      'Tul: Won-Hyo (28 movements)',
      'Gojung sogi (fixed stance) + punch',
      'Goro Chagi (hooking kick), Naeryo Chagi (downward kick)',
      '2-step sparring (Ibo Matsogi) #1–3',
      'Theory: meaning of Won-Hyo, green belt symbolism',
    ],
  ),
  BeltLevel(
    id: '5gup',
    gup: '5 GUP',
    name: 'Green → Blue Stripe',
    baseColor: _green,
    stripeColor: _blue,
    requirements: [
      'Tul: Yul-Gok (38 movements)',
      'Palkup taerigi (elbow strike), dwijibo jirugi',
      'Dwit Chagi (back piercing kick) — both legs',
      '2-step sparring full set + free sparring intro',
      'Theory: meaning of Yul-Gok (Yi I, "Confucius of Korea")',
    ],
  ),
  BeltLevel(
    id: '4gup',
    gup: '4 GUP',
    name: 'Blue',
    baseColor: _blue,
    requirements: [
      'Tul: Joong-Gun (32 movements)',
      'Kyocha sogi (X-stance), sang palmok makgi',
      'Bandae Dollyo Chagi (reverse turning kick)',
      '1-step sparring (Ilbo Matsogi) #1–3',
      'Theory: meaning of Joong-Gun (Ahn Joong-Gun)',
    ],
  ),
  BeltLevel(
    id: '3gup',
    gup: '3 GUP',
    name: 'Blue → Red Stripe',
    baseColor: _blue,
    stripeColor: _red,
    requirements: [
      'Tul: Toi-Gye (37 movements)',
      'W-shape block (san makgi) in annun sogi',
      'Twimyo Yop Chagi (flying side kick)',
      '1-step sparring full set + free sparring 2×2 min',
      'Theory: meaning of Toi-Gye (Yi Hwang)',
    ],
  ),
  BeltLevel(
    id: '2gup',
    gup: '2 GUP',
    name: 'Red',
    baseColor: _red,
    requirements: [
      'Tul: Hwa-Rang (29 movements)',
      'Combination kicking: dollyo + bandae dollyo chagi',
      'Twimyo Dollyo Chagi (flying turning kick)',
      'Free sparring 2×2 min + self-defence (hosinsul) basics',
      'Theory: meaning of Hwa-Rang, red belt symbolism',
    ],
  ),
  BeltLevel(
    id: '1gup',
    gup: '1 GUP',
    name: 'Red → Black Stripe',
    baseColor: _red,
    stripeColor: _black,
    requirements: [
      'Tul: Choong-Moo (30 movements)',
      'All previous patterns on demand',
      'Twimyo Bandae Dollyo Chagi (flying reverse turning kick)',
      'Free sparring vs two opponents + breaking (kyokpa)',
      'Theory: meaning of Choong-Moo (Admiral Yi Sun-Sin), full terminology',
    ],
  ),
];