postit: tolerate nearby rdv map cache hits

src/PostIt/PostIt.Tests/RdvPageTests.cs

@@ -0,0 +1,30 @@
+using PostIt.Views.Commands;
+
+namespace PostIt.Tests;
+
+public class RdvPageTests
+{
+    [Fact]
+    public void AreCoordinatesClose_returns_true_for_nearby_points_within_cache_tolerance()
+    {
+        var result = RdvPage.AreCoordinatesClose(
+            48.8566,
+            2.3522,
+            48.85665,
+            2.35225);
+
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void AreCoordinatesClose_returns_false_for_points_outside_cache_tolerance()
+    {
+        var result = RdvPage.AreCoordinatesClose(
+            48.8566,
+            2.3522,
+            48.85685,
+            2.3522);
+
+        Assert.False(result);
+    }
+}

src/PostIt/PostIt/Views/Commands/RdvPage.axaml.cs

@@ -22,6 +22,7 @@ public partial class RdvPage : ContentPage
     private const double DefaultLongitude = 2.3522;
     private const int DefaultZoomLevel = 4;
     private const int SelectedZoomLevel = 13;
+    internal const double ReverseGeocodingCacheToleranceDegrees = 0.0001;
     private static readonly TimeSpan ReverseGeocodingDebounce = TimeSpan.FromMilliseconds(350);
 
     private MapControl? _locationMap;
@@ -183,8 +184,9 @@ public partial class RdvPage : ContentPage
 
     private async Task TryResolveAddressAsync(RdvViewModel vm, double latitude, double longitude)
     {
-        if (_lastResolvedLatitude == latitude
+        if (_lastResolvedLatitude.HasValue
-            && _lastResolvedLongitude == longitude
+            && _lastResolvedLongitude.HasValue
+            && AreCoordinatesClose(_lastResolvedLatitude.Value, _lastResolvedLongitude.Value, latitude, longitude)
             && !string.IsNullOrWhiteSpace(_lastResolvedAddress))
         {
             vm.ApplyResolvedAddress(_lastResolvedAddress);
@@ -221,4 +223,14 @@ public partial class RdvPage : ContentPage
             vm.IsResolvingAddress = false;
         }
     }
+
+    internal static bool AreCoordinatesClose(
+        double latitudeA,
+        double longitudeA,
+        double latitudeB,
+        double longitudeB)
+    {
+        return Math.Abs(latitudeA - latitudeB) <= ReverseGeocodingCacheToleranceDegrees
+            && Math.Abs(longitudeA - longitudeB) <= ReverseGeocodingCacheToleranceDegrees;
+    }
 }