/// Thin wrapper around [SharedPreferences] for local key-value persistence.
library;

import 'dart:convert';

import 'package:shared_preferences/shared_preferences.dart';

import '../models/bank.dart';
import '../models/transaction_meta.dart';
import '../utils/constants.dart';

/// Persisted annotation store for transactions.
class TxMetaStoreData {
  const TxMetaStoreData({
    this.byId = const {},
    this.labelsByMerchant = const {},
    this.notesByMerchant = const {},
    this.exactTemplates = const {},
    this.customLabels = const [],
  });

  final Map<String, TxMeta> byId;
  final Map<String, List<String>> labelsByMerchant;
  final Map<String, String> notesByMerchant;
  final Map<String, TxExactTemplate> exactTemplates;
  final List<TxLabel> customLabels;
}

/// Cached bank payload so the app stays usable across restarts / brief outages.
class BankCache {
  const BankCache({
    required this.status,
    this.balance,
    this.transactions = const [],
  });

  final ConnectStatus status;
  final BankBalance? balance;
  final List<BankTransaction> transactions;

  Map<String, dynamic> toJson() => {
        'status': {
          'status': status.status,
          'linked': status.linked,
          'accountId': status.accountId,
          'sessionId': status.sessionId,
          'state': status.state,
          'validUntil': status.validUntil,
        },
        'balance': balance == null
            ? null
            : {
                'amount': balance!.amount,
                'currency': balance!.currency,
                'balanceType': balance!.balanceType,
              },
        'transactions': [
          for (final tx in transactions)
            {
              'date': tx.date,
              'description': tx.description,
              'amount': tx.amount,
              'currency': tx.currency,
              'pending': tx.pending,
            },
        ],
      };

  factory BankCache.fromJson(Map<String, dynamic> json) {
    final statusRaw = json['status'];
    final status = statusRaw is Map
        ? ConnectStatus.fromJson(Map<String, dynamic>.from(statusRaw))
        : ConnectStatus.disconnected;
    final balanceRaw = json['balance'];
    final balance = balanceRaw is Map
        ? BankBalance.fromJson(Map<String, dynamic>.from(balanceRaw))
        : null;
    final txsRaw = json['transactions'];
    final transactions = txsRaw is List
        ? txsRaw
            .whereType<Map>()
            .map((e) => BankTransaction.fromJson(Map<String, dynamic>.from(e)))
            .toList(growable: false)
        : const <BankTransaction>[];
    return BankCache(
      status: status,
      balance: balance,
      transactions: transactions,
    );
  }
}

/// Loads and stores user preferences. Call [init] once at startup.
class StorageService {
  StorageService({this._preferences});

  SharedPreferences? _preferences;

  Future<void> init() async {
    _preferences ??= await SharedPreferences.getInstance();
  }

  SharedPreferences get _prefs {
    final prefs = _preferences;
    if (prefs == null) {
      throw StateError('StorageService.init() must be called before use.');
    }
    return prefs;
  }

  String get themeModeName =>
      _prefs.getString(StorageKeys.themeMode) ?? 'system';

  Future<void> setThemeModeName(String value) {
    return _prefs.setString(StorageKeys.themeMode, value);
  }

  bool get useRemoteData => _prefs.getBool(StorageKeys.useRemoteData) ?? false;

  Future<void> setUseRemoteData(bool value) {
    return _prefs.setBool(StorageKeys.useRemoteData, value);
  }

  BankCache? loadBankCache() {
    final raw = _prefs.getString(StorageKeys.bankCache);
    if (raw == null || raw.isEmpty) return null;
    try {
      final decoded = jsonDecode(raw);
      if (decoded is! Map) return null;
      return BankCache.fromJson(Map<String, dynamic>.from(decoded));
    } catch (_) {
      return null;
    }
  }

  Future<void> saveBankCache(BankCache cache) {
    return _prefs.setString(StorageKeys.bankCache, jsonEncode(cache.toJson()));
  }

  Future<void> clearBankCache() {
    return _prefs.remove(StorageKeys.bankCache);
  }

  TxMetaStoreData loadTxMetaStore() {
    final raw = _prefs.getString(StorageKeys.txMeta);
    if (raw != null && raw.isNotEmpty) {
      return _decodeStore(raw);
    }

    final legacy = _prefs.getString(StorageKeys.txMetaLegacy);
    if (legacy == null || legacy.isEmpty) return const TxMetaStoreData();
    try {
      final decoded = jsonDecode(legacy);
      if (decoded is! Map) return const TxMetaStoreData();
      final byId = <String, TxMeta>{};
      final labelsByMerchant = <String, List<String>>{};
      decoded.forEach((key, value) {
        if (key is! String || value is! Map) return;
        final meta = TxMeta.fromJson(Map<String, dynamic>.from(value));
        byId[key] = meta;
        if (meta.hasLabel) {
          final desc = _descriptionFromLegacyId(key);
          if (desc != null) {
            labelsByMerchant[merchantKeyFromDescription(desc)] =
                List<String>.of(meta.labelIds);
          }
        }
      });
      return TxMetaStoreData(
        byId: byId,
        labelsByMerchant: labelsByMerchant,
      );
    } catch (_) {
      return const TxMetaStoreData();
    }
  }

  Future<void> saveTxMetaStore(TxMetaStoreData store) {
    final encoded = {
      'byId': {
        for (final e in store.byId.entries) e.key: e.value.toJson(),
      },
      'labelsByMerchant': {
        for (final e in store.labelsByMerchant.entries) e.key: e.value,
      },
      // Legacy single-label map for older builds.
      'labelByMerchant': {
        for (final e in store.labelsByMerchant.entries)
          if (e.value.isNotEmpty) e.key: e.value.first,
      },
      'categoryByDescription': {
        for (final e in store.labelsByMerchant.entries)
          if (e.value.isNotEmpty) e.key: e.value.first,
      },
      'notesByMerchant': store.notesByMerchant,
      'notesByDescription': store.notesByMerchant,
      'exactTemplates': {
        for (final e in store.exactTemplates.entries) e.key: e.value.toJson(),
      },
      'customLabels': [
        for (final label in store.customLabels) label.toJson(),
      ],
    };
    return _prefs.setString(StorageKeys.txMeta, jsonEncode(encoded));
  }

  TxMetaStoreData _decodeStore(String raw) {
    try {
      final decoded = jsonDecode(raw);
      if (decoded is! Map) return const TxMetaStoreData();
      final root = Map<String, dynamic>.from(decoded);

      final byId = <String, TxMeta>{};
      final byIdRaw = root['byId'];
      if (byIdRaw is Map) {
        byIdRaw.forEach((key, value) {
          if (key is String && value is Map) {
            byId[key] = TxMeta.fromJson(Map<String, dynamic>.from(value));
          }
        });
      }

      final labelsByMerchant = <String, List<String>>{};
      final multi = root['labelsByMerchant'];
      if (multi is Map) {
        multi.forEach((key, value) {
          if (key is! String) return;
          if (value is List) {
            final ids = [
              for (final item in value)
                if (item is String &&
                    item.isNotEmpty &&
                    item != 'uncategorized' &&
                    item != 'other')
                  item,
            ];
            if (ids.isNotEmpty) labelsByMerchant[key] = ids;
          } else if (value is String &&
              value.isNotEmpty &&
              value != 'uncategorized' &&
              value != 'other') {
            labelsByMerchant[key] = [value];
          }
        });
      } else {
        final singles =
            root['labelByMerchant'] ?? root['categoryByDescription'];
        if (singles is Map) {
          singles.forEach((key, value) {
            if (key is! String || value is! String) return;
            if (value == 'uncategorized' || value == 'other') return;
            labelsByMerchant[key] = [value];
          });
        }
      }

      final notesByMerchant = <String, String>{};
      final notesRaw = root['notesByMerchant'] ?? root['notesByDescription'];
      if (notesRaw is Map) {
        notesRaw.forEach((key, value) {
          if (key is String && value is String && value.trim().isNotEmpty) {
            notesByMerchant[key] = value;
          }
        });
      }

      final exactTemplates = <String, TxExactTemplate>{};
      final templates = root['exactTemplates'];
      if (templates is Map) {
        templates.forEach((key, value) {
          if (key is String && value is Map) {
            exactTemplates[key] =
                TxExactTemplate.fromJson(Map<String, dynamic>.from(value));
          }
        });
      }

      final customLabels = <TxLabel>[];
      final customs = root['customLabels'];
      if (customs is List) {
        for (final item in customs) {
          if (item is Map) {
            customLabels.add(
              TxLabel.fromJson(Map<String, dynamic>.from(item)),
            );
          }
        }
      }

      return TxMetaStoreData(
        byId: byId,
        labelsByMerchant: labelsByMerchant,
        notesByMerchant: notesByMerchant,
        exactTemplates: exactTemplates,
        customLabels: customLabels,
      );
    } catch (_) {
      return const TxMetaStoreData();
    }
  }

  /// Legacy id format: `date|currency|amount|description`.
  String? _descriptionFromLegacyId(String id) {
    final parts = id.split('|');
    if (parts.length < 4) return null;
    final description = parts.sublist(3).join('|');
    return description.trim().toLowerCase().replaceAll(RegExp(r'\s+'), ' ');
  }
}