import 'dart:async';
import 'dart:convert';
import 'dart:io';

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

import '../errors/network_exception.dart';
import '../errors/parse_exception.dart';
import '../errors/server_exception.dart';
import 'nominatim_result.dart';

/// Tiny wrapper around the public Nominatim geocoder. Only used in the
/// commute-settings flow to look up a home address; not called from any
/// hot path. The User-Agent header is **required** by the Nominatim usage
/// policy — without it the service throttles/blocks the client.
class NominatimSearch {
  static const _userAgent = 'MarianumMobile/1.0 (contact@elias-mueller.com)';
  static final Uri _base = Uri.parse('https://nominatim.openstreetmap.org/search');

  /// Returns up to [limit] geocoded matches for the user-typed [query].
  Future<List<NominatimResult>> run(String query, {int limit = 5}) async {
    final uri = _base.replace(
      queryParameters: {
        'q': query,
        'format': 'json',
        'limit': limit.toString(),
        'addressdetails': '0',
        'accept-language': 'de',
      },
    );

    final http.Response response;
    try {
      response = await http
          .get(uri, headers: {'User-Agent': _userAgent, 'Accept': 'application/json'})
          .timeout(const Duration(seconds: 15));
    } on SocketException catch (e) {
      throw NetworkException(technicalDetails: 'nominatim: ${e.message}');
    } on TimeoutException catch (e) {
      throw NetworkException.timeout(technicalDetails: 'nominatim: $e');
    } on http.ClientException catch (e) {
      throw NetworkException(technicalDetails: 'nominatim: ${e.message}');
    }

    if (response.statusCode > 299) {
      throw ServerException(
        statusCode: response.statusCode,
        technicalDetails: 'nominatim HTTP ${response.statusCode}',
      );
    }

    try {
      final raw = jsonDecode(utf8.decode(response.bodyBytes)) as List;
      return raw
          .map((e) => _resultFromRaw(e as Map<String, dynamic>))
          .toList(growable: false);
    } catch (e) {
      throw ParseException(technicalDetails: 'nominatim assemble: $e');
    }
  }

  static NominatimResult _resultFromRaw(Map<String, dynamic> json) {
    // Nominatim returns lat/lon as strings, not numbers. Normalise here.
    final lat = double.parse(json['lat'].toString());
    final lon = double.parse(json['lon'].toString());
    return NominatimResult(
      displayName: json['display_name'] as String? ?? '?',
      lat: lat,
      lon: lon,
    );
  }
}