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

import 'package:http/http.dart' as http;

/// Fetches public web API data used to build question text and answers.
class ExternalDataFetcher {
  ExternalDataFetcher({http.Client? client}) : _client = client ?? http.Client();

  final http.Client _client;
  final Random _random = Random();

  /// Random country with population (millions) and capital for trivia questions.
  Future<CountryFacts?> fetchRandomCountry() async {
    final http.Response response = await _client.get(
      Uri.parse(
        'https://restcountries.com/v3.1/all?fields=name,population,capital',
      ),
    );
    if (response.statusCode != 200) {
      return null;
    }
    final List<dynamic> countries =
        jsonDecode(response.body) as List<dynamic>;
    if (countries.isEmpty) {
      return null;
    }

    for (int attempt = 0; attempt < 8; attempt++) {
      final Map<String, dynamic> raw =
          countries[_random.nextInt(countries.length)] as Map<String, dynamic>;
      final int? population = raw['population'] as int?;
      final List<dynamic>? capitals = raw['capital'] as List<dynamic>?;
      final Map<String, dynamic>? nameMap =
          raw['name'] as Map<String, dynamic>?;
      final String? commonName = nameMap?['common'] as String?;
      if (population == null ||
          population < 500_000 ||
          capitals == null ||
          capitals.isEmpty ||
          commonName == null) {
        continue;
      }
      return CountryFacts(
        name: commonName,
        populationMillions: (population / 1_000_000).round(),
        capital: capitals.first as String,
      );
    }
    return null;
  }

  /// Current temperature (°C, rounded) for a European city via Open-Meteo.
  Future<WeatherFacts?> fetchRandomCityWeather() async {
    const List<({String city, double lat, double lon})> cities =
        <({String city, double lat, double lon})>[
      (city: 'Berlin', lat: 52.52, lon: 13.41),
      (city: 'Paris', lat: 48.86, lon: 2.35),
      (city: 'Madrid', lat: 40.42, lon: -3.70),
      (city: 'Rome', lat: 41.90, lon: 12.50),
      (city: 'Amsterdam', lat: 52.37, lon: 4.90),
    ];
    final ({String city, double lat, double lon}) pick =
        cities[_random.nextInt(cities.length)];
    final Uri uri = Uri.parse(
      'https://api.open-meteo.com/v1/forecast'
      '?latitude=${pick.lat}&longitude=${pick.lon}'
      '&current=temperature_2m&timezone=auto',
    );
    final http.Response response = await _client.get(uri);
    if (response.statusCode != 200) {
      return null;
    }
    final Map<String, dynamic> json =
        jsonDecode(response.body) as Map<String, dynamic>;
    final Map<String, dynamic>? current =
        json['current'] as Map<String, dynamic>?;
    final num? temp = current?['temperature_2m'] as num?;
    if (temp == null) {
      return null;
    }
    return WeatherFacts(
      city: pick.city,
      temperatureCelsius: temp.round(),
    );
  }

  void close() => _client.close();
}

class CountryFacts {
  CountryFacts({
    required this.name,
    required this.populationMillions,
    required this.capital,
  });

  final String name;
  final int populationMillions;
  final String capital;
}

class WeatherFacts {
  WeatherFacts({
    required this.city,
    required this.temperatureCelsius,
  });

  final String city;
  final int temperatureCelsius;
}