EFB/Controllers/FlightsimController.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using EFB.Sessions;
using Microsoft.Extensions.Logging;
using EFB.Models;
using EFB.MongoData;
using EFB.Models.Route;

namespace EFB.Controllers
{
    //[Route("[controller]")]
    public class FlightsimController : Controller
    {
        private readonly ILogger<FlightsimController> _logger;

        public FlightsimController(ILogger<FlightsimController> logger)
        {
            _logger = logger;
        }

        public async Task<IActionResult> Index()
        {
            //Retrieve and Check current user status
            UserModel user = HttpContext.Session.GetObject<UserModel>("User");
            if(user == null){
                TempData["Error"] = "You must be logged in before you are able to view the FlightSim Page";
                return RedirectToAction("Index", "Home");
            } 

            //Retrieve the user's latest sim position and construct it into FlightsimModel
            if (user.Route == null){
                TempData["Error"] = "You must have a route planned before you are able to view the Flightsim page";
                return RedirectToAction("Index", "Route");
            } 

            SimPositionModel latestPositionModel = await Mongo.GetLatestData(user.EMail);

            RouteModel route = await RouteModel.StringToRoute(user.Departure, user.Arrival, user.Cruise, user.Route);
            IWaypoint closest = DetermineClosest(route, latestPositionModel.LatestPosition);

            return View(new FlightsimModel(latestPositionModel, closest));

        }

        private IWaypoint DetermineClosest(RouteModel route, SimPosition currentPosition){
            IWaypoint closest = null;
            float closestDistance = float.MaxValue;
            //Assuming that we are on the earth for simplicity
            IWaypoint waypoint = route.Departure;
            while (waypoint.Next != null)
            {
                int earthRadius = 6371;
                float distanceLat = DegreesToRadians(waypoint.Latitude - currentPosition.Latitude);
                float distanceLon = DegreesToRadians(waypoint.Longitude - currentPosition.Longitude);

                float latitude1 = DegreesToRadians(currentPosition.Latitude);
                float latitude2 = DegreesToRadians(waypoint.Latitude);

                var a = Math.Sin(distanceLat/2) * Math.Sin(distanceLat/2) + Math.Sin(distanceLon/2) * Math.Sin(distanceLon/2) * Math.Cos(latitude1) * Math.Cos(latitude2);
                var c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1-a));

                float distance = (float)(earthRadius * c);

                if (distance < closestDistance)
                {
                    closest = waypoint;
                    closestDistance = distance;
                }
                waypoint = waypoint.Next;
            }
            return closest;
        }
        private float DegreesToRadians(float degrees){
            return (float)(degrees * Math.PI / 180);
        } 

        [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]
        public IActionResult Error()
        {
            return View("Error!");
        }
    }
}