import 'dart:convert';

import 'package:shared_preferences/shared_preferences.dart';
import '../../../utils/tools/app_sp.dart';

/// 本地搜索历史（SharedPreferences），key 与 [AppSp] 规则一致（`.search.history`）。
class SearchUtil {
  SearchUtil._();

  static const String _storageKey = 'sky.search.history';
  static const int _maxHistory = 20;

  static Future<List<String>> _readList(SharedPreferences prefs) async {
    final raw = prefs.getString(_storageKey);
    if (raw == null || raw.isEmpty) return [];
    try {
      final decoded = jsonDecode(raw);
      if (decoded is! List) return [];
      return decoded.map((e) => e.toString()).where((s) => s.isNotEmpty).toList();
    } catch (_) {
      return [];
    }
  }

  static Future<void> _writeList(SharedPreferences prefs, List<String> list) async {
    await prefs.setString(_storageKey, jsonEncode(list));
  }

  /// 查询搜索历史列表（新记录在前）。
  static Future<List<String>> getSearchList() async {
    final prefs = await AppSp.getInstance();
    return _readList(prefs);
  }

  /// 添加一条搜索；去重、去空白，并移到最前。
  static Future<void> addSearch(String keyword) async {
    final q = keyword.trim();
    if (q.isEmpty) return;

    final prefs = await AppSp.getInstance();
    final list = await _readList(prefs);
    list.removeWhere((e) => e == q);
    list.insert(0, q);
    if (list.length > _maxHistory) {
      list.removeRange(_maxHistory, list.length);
    }
    await _writeList(prefs, list);
  }

  /// 删除单条搜索记录。
  static Future<void> deleteSearch(String keyword) async {
    final prefs = await AppSp.getInstance();
    final list = await _readList(prefs);
    list.removeWhere((e) => e == keyword);
    await _writeList(prefs, list);
  }

  /// 清空全部搜索历史。
  static Future<void> clearAllSearch() async {
    final prefs = await AppSp.getInstance();
    await prefs.remove(_storageKey);
  }
}