1 files changed, 89 insertions, 0 deletions
diff --git a/src/Cepis/GeoConverter.cs b/src/Cepis/GeoConverter.cs
new file mode 100644
index 0000000..f5c78de
--- /dev/null
+++ b/src/Cepis/GeoConverter.cs
@@ -0,0 +1,89 @@
+using System.Globalization;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace Cepis;
+
+/// <summary>
+/// Reads the <c>geo</c> block, yielding <see langword="null"/> for anything it
+/// cannot make sense of.
+/// </summary>
+/// <remarks>
+/// A malformed coordinate is not worth losing the whole address over: the rest
+/// of the response is still useful, and an address with no coordinate is a
+/// shape callers already handle, since about 43% of CEPs have none.
+/// </remarks>
+internal sealed class GeoConverter : JsonConverter<Geo?>
+{
+    public override Geo? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        using var document = JsonDocument.ParseValue(ref reader);
+        var root = document.RootElement;
+        if (root.ValueKind != JsonValueKind.Object)
+        {
+            return null;
+        }
+
+        var lat = ReadDouble(root, "lat");
+        var lon = ReadDouble(root, "lon");
+        var raio = ReadDouble(root, "raio_m");
+        var precisao = ReadString(root, "precisao");
+
+        if (lat is null || lon is null || raio is null || precisao is null)
+        {
+            return null;
+        }
+
+        return new Geo
+        {
+            Lat = lat.Value,
+            Lon = lon.Value,
+            RaioM = (int)Math.Round(raio.Value),
+            Precisao = precisao,
+        };
+    }
+
+    public override void Write(Utf8JsonWriter writer, Geo? value, JsonSerializerOptions options)
+    {
+        ArgumentNullException.ThrowIfNull(writer);
+
+        if (value is null)
+        {
+            writer.WriteNullValue();
+            return;
+        }
+
+        writer.WriteStartObject();
+        writer.WriteNumber("lat", value.Lat);
+        writer.WriteNumber("lon", value.Lon);
+        writer.WriteNumber("raio_m", value.RaioM);
+        writer.WriteString("precisao", value.Precisao);
+        writer.WriteEndObject();
+    }
+
+    private static double? ReadDouble(JsonElement owner, string name)
+    {
+        if (!owner.TryGetProperty(name, out var element))
+        {
+            return null;
+        }
+
+        return element.ValueKind switch
+        {
+            JsonValueKind.Number => element.TryGetDouble(out var number) ? number : null,
+            JsonValueKind.String => double.TryParse(
+                element.GetString(),
+                NumberStyles.Float,
+                CultureInfo.InvariantCulture,
+                out var parsed)
+                ? parsed
+                : null,
+            _ => null,
+        };
+    }
+
+    private static string? ReadString(JsonElement owner, string name) =>
+        owner.TryGetProperty(name, out var element) && element.ValueKind == JsonValueKind.String
+            ? element.GetString()
+            : null;
+}