/// Ported from `com.rippr.Config`.
///
/// Runtime configuration. The upload endpoint is intentionally empty by default —
/// recording must work with no server at all, and uploading is opt-in.
library;

import 'dart:io';
import 'dart:math';

import 'package:shared_preferences/shared_preferences.dart';

import '../domain/models.dart' show UnitSystem;

const _keyEndpoint = 'upload_endpoint';
const _keyDeviceId = 'device_id';
const _keyMapEnabled = 'map_enabled';
const _keyUnitSystem = 'unit_system';

/// Countries that did not adopt metric for everyday distances. Not exhaustive — a
/// best-effort default, not a claim of authority. Anyone can override it in Settings.
const _imperialCountryCodes = {'US', 'LR', 'MM'};

class Config {
  Config(this._prefs);

  final SharedPreferences _prefs;

  static Future<Config> load() async =>
      Config(await SharedPreferences.getInstance());

  String get uploadEndpoint => _prefs.getString(_keyEndpoint) ?? '';

  Future<void> setUploadEndpoint(String url) =>
      _prefs.setString(_keyEndpoint, url.trim());

  /// Whether trip detail renders a map at all.
  ///
  /// When off the map widget is never created, so no tile is ever requested — a real
  /// short-circuit, not a hidden view. The map only ever exists inside a visible screen's
  /// lifecycle; the recorder never touches it.
  bool get mapEnabled => _prefs.getBool(_keyMapEnabled) ?? true;

  Future<void> setMapEnabled(bool enabled) =>
      _prefs.setBool(_keyMapEnabled, enabled);

  /// Metric unless the device's own locale says otherwise. Explicit user choice, once
  /// made, always wins over the locale guess.
  UnitSystem get unitSystem {
    final stored = _prefs.getString(_keyUnitSystem);
    if (stored != null) {
      return UnitSystem.values.firstWhere(
        (u) => u.name == stored,
        orElse: () => _localeDefaultUnitSystem(),
      );
    }
    return _localeDefaultUnitSystem();
  }

  Future<void> setUnitSystem(UnitSystem system) =>
      _prefs.setString(_keyUnitSystem, system.name);

  static UnitSystem _localeDefaultUnitSystem() {
    // "en_US", "en_US.UTF-8" and similar; the region is the second underscore- or
    // hyphen-delimited segment when present.
    final parts = Platform.localeName.split(RegExp('[_-]'));
    final region = parts.length > 1 ? parts[1].toUpperCase() : '';
    return _imperialCountryCodes.contains(region)
        ? UnitSystem.imperial
        : UnitSystem.metric;
  }

  /// Stable per-install id so a server can distinguish riders in a group.
  String get deviceId {
    final existing = _prefs.getString(_keyDeviceId);
    if (existing != null) return existing;
    final generated = _randomId();
    // Fire-and-forget: the value is returned immediately either way, and a lost write
    // only costs a new id next launch.
    _prefs.setString(_keyDeviceId, generated);
    return generated;
  }

  /// A UUID v4, without pulling in a package for sixteen bytes.
  static String _randomId() {
    final rng = Random.secure();
    final bytes = List<int>.generate(16, (_) => rng.nextInt(256));
    bytes[6] = (bytes[6] & 0x0f) | 0x40;
    bytes[8] = (bytes[8] & 0x3f) | 0x80;
    String hex(int start, int end) => bytes
        .sublist(start, end)
        .map((b) => b.toRadixString(16).padLeft(2, '0'))
        .join();
    return '${hex(0, 4)}-${hex(4, 6)}-${hex(6, 8)}-${hex(8, 10)}-${hex(10, 16)}';
  }
}