import 'dart:convert';
import 'dart:math';

import 'package:shared_preferences/shared_preferences.dart';

/// Device-local bookmarks for public (unauthenticated) app usage.
class LocalBookmarksService {
  static const _storageKey = 'local_bookmarks';
  static const _deviceIdKey = 'device_id';

  static Future<String> deviceId() async {
    final prefs = await SharedPreferences.getInstance();
    var id = prefs.getString(_deviceIdKey);
    if (id == null || id.isEmpty) {
      id = '${DateTime.now().millisecondsSinceEpoch}_${Random().nextInt(1 << 32)}';
      await prefs.setString(_deviceIdKey, id);
    }
    return id;
  }

  static Future<List<Map<String, dynamic>>> getAll() async {
    final prefs = await SharedPreferences.getInstance();
    final raw = prefs.getString(_storageKey);
    if (raw == null || raw.isEmpty) return [];
    final decoded = jsonDecode(raw);
    if (decoded is! List) return [];
    return decoded
        .map((e) => Map<String, dynamic>.from(e as Map))
        .toList();
  }

  static Future<void> _saveAll(List<Map<String, dynamic>> bookmarks) async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_storageKey, jsonEncode(bookmarks));
  }

  static Future<Map<String, dynamic>?> findByDataset(String dataset) async {
    final bookmarks = await getAll();
    for (final b in bookmarks) {
      if (b['data_set'] == dataset || b['dataset'] == dataset) {
        return b;
      }
    }
    return null;
  }

  static Future<Map<String, dynamic>> add({
    required String dataset,
    required String bgColor,
    required String mainTopic,
    required String title,
    required String keyParam,
  }) async {
    final bookmarks = await getAll();
    final id = '${DateTime.now().millisecondsSinceEpoch}_${Random().nextInt(1 << 32)}';
    final entry = {
      'id': id,
      'data_set': dataset,
      'dataset': dataset,
      'bgColor': bgColor,
      'main_topic': mainTopic,
      'mainTopic': mainTopic,
      'data_set_tile_heading': title,
      'title': title,
      'keyParam': keyParam,
      'created': DateTime.now().toIso8601String(),
    };
    bookmarks.removeWhere(
      (b) => b['data_set'] == dataset || b['dataset'] == dataset,
    );
    bookmarks.add(entry);
    await _saveAll(bookmarks);
    return entry;
  }

  static Future<void> remove(String id) async {
    final bookmarks = await getAll();
    bookmarks.removeWhere((b) => b['id'] == id);
    await _saveAll(bookmarks);
  }
}