Make exhibits accessible only within a certain range.

HiP-DataStore.Model/Entity/Exhibit.cs

@@ -16,6 +16,8 @@ public class Exhibit : ContentBase
 
         public float Longitude { get; set; }
 
+        public float AccessRadius { get; set; }
+
         [BsonElement]
         public DocRef<MediaElement> Image { get; private set; } =
             new DocRef<MediaElement>(ResourceType.Media.Name);
@@ -42,6 +44,7 @@ public Exhibit(ExhibitArgs args)
             Status = args.Status;
             Tags.Add(args.Tags?.Select(id => (BsonValue)id));
             Pages.Add(args.Pages?.Select(id => (BsonValue)id));
+            AccessRadius = args.AccessRadius;
         }
     }
 }

HiP-DataStore.Model/Rest/ExhibitArgs.cs

@@ -30,6 +30,12 @@ public class ExhibitArgs
 
         public List<int> Pages { get; set; }
 
+        /// <summary>
+        /// The radius (in km) in which the exhibit can be accessed.
+        /// </summary>
+        [Range(0.001, 1000)]
+        public float AccessRadius { get; set; }
+
         public IEnumerable<EntityId> GetReferences()
         {
             if (Image != null)

HiP-DataStore.Model/Rest/ExhibitQueryArgs.cs

@@ -5,5 +5,9 @@ namespace PaderbornUniversity.SILab.Hip.DataStore.Model.Rest
     public class ExhibitQueryArgs : QueryArgs
     {
         public IList<int> OnlyRoutes { get; set; }
+
+        public float? Latitude { get; set; }
+
+        public float? Longitude { get; set; }
     }
 }

HiP-DataStore.Model/Rest/ExhibitResult.cs

@@ -20,6 +20,8 @@ public class ExhibitResult
 
         public float Longitude { get; set; }
 
+        public float AccessRadius { get; set; }
+
         public bool Used { get; set; }
 
         public string UserId { get; set; }
@@ -46,6 +48,7 @@ public ExhibitResult(Exhibit x)
             Image = (int?)x.Image.Id;
             Latitude = x.Latitude;
             Longitude = x.Longitude;
+            AccessRadius = x.AccessRadius;
             Used = x.Referencers.Count > 0; // an exhibit is in use if it is contained in (i.e. referenced by) a route
             Pages = x.Pages.Ids.Select(id => (int)id).ToArray();
             Status = x.Status;

HiP-DataStore/Controllers/ExhibitsController.cs

@@ -76,6 +76,7 @@ public IActionResult Get([FromQuery]ExhibitQueryArgs args)
 
                 var exhibits = query
                     .FilterByIds(args.Exclude, args.IncludeOnly)
+                    .FilterByLocation(args.Latitude, args.Longitude)
                     .FilterByUser(args.Status,User.Identity)
                     .FilterByStatus(args.Status, User.Identity)
                     .FilterByTimestamp(args.Timestamp)

HiP-DataStore/Controllers/QueryHelper.cs

@@ -7,6 +7,7 @@
 using PaderbornUniversity.SILab.Hip.DataStore.Model.Rest;
 using System.Security.Principal;
 using PaderbornUniversity.SILab.Hip.DataStore.Utility;
+using static System.Math;
 
 namespace PaderbornUniversity.SILab.Hip.DataStore.Controllers
 {
@@ -57,6 +58,36 @@ public static IQueryable<T> FilterByUser<T>(this IQueryable<T> query, ContentSta
             return query.FilterIf(!isAllowedGetAll, x =>
                         ((status == ContentStatus.All) && (x.Status == ContentStatus.Published)) || (x.UserId == user.GetUserIdentity()));
         }
+
+        /// <summary>
+        /// Returns all entries that are located within the radius, defined within the entry itself, around the given latitude and longitude.
+        /// If none or only one coordinate is given, all entries are returned.
+        /// </summary>
+        public static IQueryable<Exhibit> FilterByLocation(this IQueryable<Exhibit> query, float? latitude, float? longitude)
+        {
+            if (latitude != null && longitude != null)
+            {
+                return query.ToList()
+                    .Where(o => GetDistanceFromLatLonInKm(o.Latitude, o.Longitude, latitude.Value, longitude.Value) <= o.AccessRadius)
+                    .AsQueryable();
+            }
+            return query;
+        }
+
+        /// <summary>
+        /// Calculates the distance between two points of latitude and longitude in km.
+        /// </summary>
+        private static double GetDistanceFromLatLonInKm(float lat1, float lon1, float lat2, float lon2)
+        {
+            float dLat = (lat2 - lat1) * (float)PI / 180;
+            float dLon = (lon2 - lon1) * (float)PI / 180;
+
+            double a = Sin(dLat / 2) * Sin(dLat / 2) 
+                + Cos(lat1 * PI / 180) * Cos(lat2 * PI / 180) 
+                * Sin(dLon / 2) * Sin(dLon / 2);
+            return 2 * Atan2(Sqrt(a), Sqrt(1-a)) * 6378;
+        }
+
         /// <summary>
         /// Executes the query to determine the number of results, then retrieves a subset of the results
         /// (determined by <paramref name="page"/> and <paramref name="pageSize"/>) and projects them to objects of

HiP-DataStore/Migrations/Migration6AccessRadius.cs

@@ -0,0 +1,32 @@
+using PaderbornUniversity.SILab.Hip.DataStore.Model.Events;
+using PaderbornUniversity.SILab.Hip.EventSourcing.Migrations;
+using System.Threading.Tasks;
+
+namespace PaderbornUniversity.SILab.Hip.DataStore.Migrations
+{
+    /// <summary>
+    /// Updating to version 6. Version 6 adds the ability to specify an access radius (in km) for an exhibit.
+    /// In prior versions, exhibits don't have this property, so a default value is assigned in this migration.
+    /// </summary>
+    [StreamMigration(from: 5, to: 6)]
+    public class Migration6AccessRadius : IStreamMigration
+    {
+        public async Task MigrateAsync(IStreamMigrationArgs e)
+        {
+            var events = e.GetExistingEvents();
+
+            while (await events.MoveNextAsync())
+            {
+                // ReSharper disable once CompareOfFloatsByEqualityOperator
+                if (events.Current is ExhibitCreated exhibitCreated && exhibitCreated.Properties.AccessRadius == 0)
+                {
+                    // If AccessRadius is still 0, we assume that this exhibit was created in an earlier version
+                    // of DataStore => thus, we now assign it a default radius of 10 meters
+                    exhibitCreated.Properties.AccessRadius = .01f;
+                }
+
+                e.AppendEvent(events.Current);
+            }
+        }
+    }
+}