import 'dart:convert';

import 'package:flutter/foundation.dart';
import 'package:http/http.dart' as http;
import 'package:latlong2/latlong.dart' show LatLng;

// ── Routing ─────────────────────────────────────────────────────────────────

/// A driving route between two points, from OSRM's public router.
///
/// Replaces the Directions API call, which needed the revoked key. Same shape
/// of answer — an ordered list of coordinates — so the callers' route drawing,
/// distance table and camera fitting are untouched.
class MilerRouter {
  static const String _host = 'https://router.project-osrm.org';

  /// Sent with every request. OSRM's demo server, like OSM's tile server,
  /// blocks anonymous clients first.
  static const String _agent = 'com.doormile.partner';

  /// The road geometry from [start] to [end], or an empty list.
  ///
  /// Never throws: a route screen with no line is a degraded screen, but a
  /// route screen that crashed is a rider standing in the street with nothing.
  /// Callers fall back to the direct line on an empty answer.
  static Future<List<LatLng>> route(LatLng start, LatLng end) async {
    final uri = Uri.parse(
      '$_host/route/v1/driving/'
      '${start.longitude},${start.latitude};${end.longitude},${end.latitude}'
      '?overview=full&geometries=geojson',
    );

    try {
      final res = await http
          .get(uri, headers: const {'User-Agent': _agent})
          .timeout(const Duration(seconds: 8));
      if (res.statusCode != 200) {
        debugPrint(
          '[MAP] OSRM ${res.statusCode} — falling back to a direct line.',
        );
        return const [];
      }

      final body = jsonDecode(res.body) as Map<String, dynamic>;
      if (body['code'] != 'Ok') {
        debugPrint('[MAP] OSRM said ${body['code']} — direct line instead.');
        return const [];
      }

      final routes = body['routes'] as List<dynamic>?;
      if (routes == null || routes.isEmpty) return const [];

      final coords =
          (routes.first as Map<String, dynamic>)['geometry']['coordinates']
              as List<dynamic>;

      // GeoJSON is [longitude, latitude] — the opposite order to everything
      // else in this app, and a silent way to end up routing through the sea.
      return [
        for (final c in coords)
          LatLng((c[1] as num).toDouble(), (c[0] as num).toDouble()),
      ];
    } catch (e) {
      debugPrint('[MAP] OSRM unreachable ($e) — direct line instead.');
      return const [];
    }
  }

  /// Road distance in metres between two points, or null when the router
  /// cannot answer.
  ///
  /// Replaces a direct call to the Google Directions API in
  /// `PickupsController`, which was reading the same revoked key and therefore
  /// silently falling back to straight-line distance on every trip — the number
  /// riders are *paid* on.
  static Future<double?> roadDistanceMetres(LatLng start, LatLng end) async {
    final uri = Uri.parse(
      '$_host/route/v1/driving/'
      '${start.longitude},${start.latitude};${end.longitude},${end.latitude}'
      '?overview=false',
    );
    try {
      final res = await http
          .get(uri, headers: const {'User-Agent': _agent})
          .timeout(const Duration(seconds: 6));
      if (res.statusCode != 200) return null;
      final body = jsonDecode(res.body) as Map<String, dynamic>;
      if (body['code'] != 'Ok') return null;
      final routes = body['routes'] as List<dynamic>?;
      if (routes == null || routes.isEmpty) return null;
      final d = (routes.first as Map<String, dynamic>)['distance'];
      return d is num ? d.toDouble() : null;
    } catch (e) {
      debugPrint('[ROUTE] OSRM distance unavailable ($e)');
      return null;
    }
  }
}