// Represents a collection of landmarks that represent a journey
// Different instances of a Trip can be saved and loaded by the user

import 'dart:collection';
import 'dart:convert';

import 'package:fast_network_navigation/structs/landmark.dart';
import 'package:shared_preferences/shared_preferences.dart';

class Trip {
  final String uuid;
  final String cityName;
  // TODO: cityName should be inferred from coordinates of the Landmarks
  final LinkedList<Landmark> landmarks;
  // could be empty as well

  Trip({
    required this.uuid,
    required this.cityName,
    required this.landmarks,
    });

  factory Trip.fromJson(Map<String, dynamic> json) {
    return Trip(
      uuid: json['uuid'],
      cityName: json['cityName'],
      landmarks: LinkedList()
    );
  }

  factory Trip.fromPrefs(SharedPreferences prefs, String uuid) {
    String? content = prefs.getString('trip_$uuid');
    Map<String, dynamic> json = jsonDecode(content!);
    Trip trip = Trip.fromJson(json);
    String? firstUUID = json['entry_uuid'];
    appendLandmarks(trip.landmarks, prefs, firstUUID);
    return trip;
  }
}

// Helper

appendLandmarks(LinkedList<Landmark> landmarks, SharedPreferences prefs, String? firstUUID) {
  while (firstUUID != null) {
    var (head, nextUUID) = getLandmarkFromPrefs(prefs, firstUUID);
    landmarks.add(head);
    firstUUID = nextUUID;
  }
}