/// <summary>
/// Accepts the GeoJson coordinates property, and iterates the top level array to determine
/// which of the four schemas the coordinates match.
/// </summary>
/// <param name="reader">A Utf8JsonReader positioned at the GeoJson coordinates property.</param>
/// <returns>A reader which will parse out correct parser based on the schema detected.</returns>
/// <exception cref="JsonException"></exception>
public static GeoJsonCoordinateReader Create(ref Utf8JsonReader reader)
{
GeoJsonCoordinateReader result;
reader.Expect(JsonTokenType.StartArray);
int detectedLevel = 0;
// How many nested StartArray tokens we find identifies which of the four schemas we're dealing with
for (; reader.Read() && reader.TokenType == JsonTokenType.StartArray; detectedLevel++)
{
if (detectedLevel == 4)
{
throw new JsonException($"Deserialization failed. GeoJson property '{GeoJsonConstants.CoordinatesPropertyName}' does not contain recognizable GeoJson.");
}
}
reader.Expect(JsonTokenType.Number);
switch (detectedLevel)
{
case 0:
result = new LevelZeroGeoJsonCoordinateReader();
break;
case 1:
result = new LevelOneGeoJsonCoordinateReader();
break;
case 2:
result = new LevelTwoGeoJsonCoordinateReader();
break;
default:
result = new LevelThreeGeoJsonCoordinateReader();
break;
}
result.Process(ref reader);
return(result);
}
/// <summary>
/// Called when a GeometryCollection is either the top level type, or when a GeometryCollection has been nested inside
/// another GeometryCollection (which is legal, but apparently discouraged.)
/// </summary>
/// <param name="reader">A Utf8JsonReader positioned at the beginning of the geometries array.</param>
/// <returns>The list of Geographies which were extracted.</returns>
private List <Geography> ProcessGeometryCollection(ref Utf8JsonReader reader)
{
List <Geography> result = new List <Geography>();
reader.Expect(JsonTokenType.StartArray);
while (reader.Read() && reader.TokenType != JsonTokenType.EndArray)
{
Geography geography = ProcessSingleGeography(ref reader);
result.Add(geography);
}
return(result);
}
/// <summary>
/// Some GeoJson documents define a single geography, e.g. Point and MultiPolygon. GeometryCollection on the other
/// hand contains a list of Geographies specified not in the coordinates property, but in the geometries property.
/// This methodwill be called at the top level by Read(), and in the case of a GeometryCollection, once for every
/// entry in its geometries array.
/// </summary>
/// <param name="reader"></param>
/// <returns></returns>
/// <exception cref="JsonException"></exception>
private Geography ProcessSingleGeography(ref Utf8JsonReader reader)
{
string type = null;
GeoJsonCoordinateReader geoJsonCoordinateReader = null;
List <Geography> geographies = null;
reader.Expect(JsonTokenType.StartObject);
while (reader.Read() && reader.TokenType != JsonTokenType.EndObject)
{
reader.Expect(JsonTokenType.PropertyName);
string propertyName = reader.GetString();
reader.Read();
if (string.Equals(GeoJsonConstants.TypePropertyName, propertyName, StringComparison.Ordinal))
{
reader.Expect(JsonTokenType.String);
type = reader.GetString();
}
else if (string.Equals(GeoJsonConstants.CoordinatesPropertyName, propertyName, StringComparison.Ordinal))
{
geoJsonCoordinateReader = GeoJsonCoordinateReader.Create(ref reader);
}
else if (string.Equals(GeoJsonConstants.GeometriesPropertyName, propertyName, StringComparison.Ordinal))
{
geographies = ProcessGeometryCollection(ref reader);
}
else
{
reader.Skip();
}
}
if (type == null)
{
throw new JsonException($"Deserialization failed. Required GeoJson property '{GeoJsonConstants.TypePropertyName}' not found.");
}
if (!TypeNames.Contains(type))
{
string valid = TypeNames.FirstOrDefault(z => z.Equals(type, StringComparison.OrdinalIgnoreCase));
if (valid != null)
{
throw new JsonException($"Deserialization failed. GeoJson property '{GeoJsonConstants.TypePropertyName}' values are case sensitive. Use '{valid}' instead.");
}
throw new JsonException($"Deserialization failed. GeoJson property '{GeoJsonConstants.TypePropertyName}' contains an invalid value: '{type}'.");
}
if (geoJsonCoordinateReader != null)
{
return(geoJsonCoordinateReader.GetGeography(type));
}
else if (geographies != null)
{
return(GeographyFactory.Collection().Create(geographies));
}
else
{
if (type == GeoJsonConstants.GeometryCollectionTypeName)
{
throw new JsonException($"Deserialization failed. Required GeoJson property '{GeoJsonConstants.GeometriesPropertyName}' not found.");
}
else
{
throw new JsonException($"Deserialization failed. Required GeoJson property '{GeoJsonConstants.CoordinatesPropertyName}' not found.");
}
}
}
/// <inheritdoc/>
public override object Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
{
if (reader.TokenType == JsonTokenType.Null)
{
return(null);
}
string type = default;
double?longitude = default;
double?latitude = default;
reader.Expect(JsonTokenType.StartObject);
while (reader.Read() && reader.TokenType != JsonTokenType.EndObject)
{
reader.Expect(JsonTokenType.PropertyName);
string propertyName = reader.GetString();
reader.Read();
if (string.Equals(TypePropertyName, propertyName, StringComparison.Ordinal))
{
reader.Expect(JsonTokenType.String);
type = reader.GetString();
}
else if (string.Equals(CoordinatesPropertyName, propertyName, StringComparison.Ordinal))
{
reader.Expect(JsonTokenType.StartArray);
// Longitude
reader.Read();
reader.Expect(JsonTokenType.Number);
longitude = reader.GetDouble();
// Latitude
reader.Read();
reader.Expect(JsonTokenType.Number);
latitude = reader.GetDouble();
// Skip the rest.
do
{
reader.Read();
} while (reader.TokenType != JsonTokenType.EndArray);
}
else
{
reader.Skip();
}
}
if (!string.Equals(PointTypeName, type, StringComparison.Ordinal))
{
throw new JsonException($"Deserialization of {nameof(GeographyPoint)} failed. Expected geographic type: '{PointTypeName}'.");
}
if (!longitude.HasValue || !latitude.HasValue)
{
throw new JsonException($"Deserialization of {nameof(GeographyPoint)} failed. Expected both longitude and latitude.");
}
return(GeographyPoint.Create(latitude.Value, longitude.Value));
}