From bf96a0e8a02bc04aa80e24d51b8f139af380b9e2 Mon Sep 17 00:00:00 2001
From: ArneD <dumarey.arne@gmail.com>
Date: Thu, 30 May 2024 12:25:22 +0200
Subject: [PATCH] fix: use a buffer to calculate if building overlaps

---
 .../BuildingGeometryContext.cs                | 34 +++++++++++++++++--
 .../OverlappingBuildingGeometryTests.cs       | 23 +++++++++++++
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/src/BuildingRegistry.Api.BackOffice.Handlers.Lambda/BuildingGeometryContext.cs b/src/BuildingRegistry.Api.BackOffice.Handlers.Lambda/BuildingGeometryContext.cs
index 8181bfdcd..e6c159d83 100644
--- a/src/BuildingRegistry.Api.BackOffice.Handlers.Lambda/BuildingGeometryContext.cs
+++ b/src/BuildingRegistry.Api.BackOffice.Handlers.Lambda/BuildingGeometryContext.cs
@@ -3,11 +3,14 @@
     using Building;
     using Infrastructure;
     using Microsoft.EntityFrameworkCore;
+    using NetTopologySuite.Geometries;
+    using NetTopologySuite.Operation.Buffer;
 
     public class BuildingGeometryContext : DbContext, IBuildingGeometries
     {
-        public DbSet<BuildingGeometryData> BuildingGeometries => Set<BuildingGeometryData>();
+        private const double AllowedOverlapPercentage = 0.05;
 
+        public DbSet<BuildingGeometryData> BuildingGeometries => Set<BuildingGeometryData>();
         public BuildingGeometryContext() { }
 
         // This needs to be DbContextOptions<T> for Autofac!
@@ -63,10 +66,37 @@ public ICollection<BuildingGeometryData> GetOverlappingBuildings(
                     && !building.IsRemoved
                     && boundingBox.Intersects(building.SysGeometry))
                 .ToList()
-                .Where(building => geometry.Intersects(building.SysGeometry))
+                .Where(building => HasTooMuchOverlap(geometry, building.SysGeometry))
                 .ToList();
 
             return overlappingBuildings;
         }
+
+        private static bool HasTooMuchOverlap(Geometry newBuildingGeometry, Geometry? existingBuildingGeometry)
+        {
+            if (existingBuildingGeometry is null)
+            {
+                return false;
+            }
+
+            try
+            {
+                var overlapArea = newBuildingGeometry.Intersection(existingBuildingGeometry).Area;
+                var newBuildingGeometryOverlapPercentage = overlapArea / newBuildingGeometry.Area;
+                var existingBuildingGeometryOverlapPercentage = overlapArea / existingBuildingGeometry.Area;
+
+                return newBuildingGeometryOverlapPercentage > AllowedOverlapPercentage
+                    || existingBuildingGeometryOverlapPercentage > AllowedOverlapPercentage;
+            }
+            catch (TopologyException topologyException)
+            {
+                // Consider buildings that Intersect, but fail with "found non-noded intersection" on calculating, to have an overlap value of 0
+                if (topologyException.Message.Contains("found non-noded intersection", StringComparison.InvariantCultureIgnoreCase))
+                    return false;
+
+                // any other TopologyException should be treated normally
+                throw;
+            }
+        }
     }
 }
diff --git a/test/BuildingRegistry.Tests/BackOffice/Lambda/OverlappingBuildingGeometryTests.cs b/test/BuildingRegistry.Tests/BackOffice/Lambda/OverlappingBuildingGeometryTests.cs
index 5ff13622f..51648a8c5 100644
--- a/test/BuildingRegistry.Tests/BackOffice/Lambda/OverlappingBuildingGeometryTests.cs
+++ b/test/BuildingRegistry.Tests/BackOffice/Lambda/OverlappingBuildingGeometryTests.cs
@@ -134,6 +134,29 @@ public void WithBuildingOverlappingGeometryAndIdenticalId_ShouldReturnNothing()
             result.Should().BeEmpty();
         }
 
+        [Fact]
+        public void WithOverlappingBuilding_ShouldReturnNothing()
+        {
+            var polygon1 = CreateGeometry("150515.51954216015 193984.87173669986 150514.00391716015 193976.65298669986 150510.30950881125 193977.33427493152 150509.72481561470 193974.16367058750 150500.24419151392 193975.91199860617 150501.16168397170 193980.88726698520 150506.17659092674 193979.96246475200 150507.35941666557 193986.37655071693 150515.51954216015 193984.87173669986");
+            var polygon2 = CreateGeometry("150527.43725961447 193983.04583268613 150515.52737160772 193984.85690468922 150513.92218761146 193976.26362468302 150513.68020360917 193974.55764068291 150519.21812361479 193973.77197667956 150518.91988360882 193971.80333667994 150522.89082761109 193971.20173668116 150526.00993161649 193973.88960868120 150527.43725961447 193983.04583268613");
+
+            _buildingGeometryContext.BuildingGeometries
+                .Add(new BuildingGeometryData(
+                    2,
+                    BuildingStatus.Realized,
+                    BuildingGeometryMethod.MeasuredByGrb,
+                    polygon2,
+                    false));
+
+            _buildingGeometryContext.SaveChanges();
+
+            var result = _buildingGeometryContext.GetOverlappingBuildings(
+                new BuildingPersistentLocalId(1),
+                ExtendedWkbGeometry.CreateEWkb(polygon1.AsBinary())!);
+
+            result.Should().BeEmpty();
+        }
+
         private static Geometry CreateGeometry(string coordinates)
             => GmlHelpers.CreateGmlReader().Read(
                 "<gml:Polygon srsName=\"https://www.opengis.net/def/crs/EPSG/0/31370\" xmlns:gml=\"http://www.opengis.net/gml/3.2\">" +