Support FeatureCollection and MultiPolygon in geozones

We're reworking the format validation to correctly interpret feature
collection, feature, and geometry, according to RFC 7946 [1].

Since Leaflet interprets GeoJSON format, we're rendering the GeoJSON as
a layer instead of as a set of points. For that, we're normalizing the
GeoJSON to make sure it contains either a Feature or a
FeatureCollection. We're also adding the Leaflet images to the assets
path so the markers used for point geometries are rendered correctly.

Note we no longer allow a GeoJSON containing a geometry but not a
defined type. Since there might be invalid GeoJSON in existing Consul
Democracy databases, we're normalizing these existing geometry objects
to be part of a feature object.

We're also wrapping the outline points in a FeatureCollection object
because most of the large GIS systems eg ArcGIS, QGIS export geojson as
a complete FeatureCollection.

[1] https://datatracker.ietf.org/doc/html/rfc7946

Co-authored-by: Javi Martín <javim@elretirao.net>

app/models/concerns/geojson_format_validator.rb

@@ -3,8 +3,13 @@ class GeojsonFormatValidator < ActiveModel::EachValidator
     if value.present?
       geojson = parse_json(value)
 
-      unless geojson?(geojson)
+      unless valid_geojson?(geojson)
         record.errors.add(attribute, :invalid)
+        return
+      end
+
+      unless valid_coordinates?(geojson)
+        record.errors.add(attribute, :invalid_coordinates)
       end
     end
   end
@@ -12,12 +17,91 @@ class GeojsonFormatValidator < ActiveModel::EachValidator
   private
 
     def parse_json(geojson_data)
-      JSON.parse(geojson_data) rescue nil
+      JSON.parse(geojson_data)
+    rescue JSON::ParserError
+      nil
     end
 
-    def geojson?(geojson)
+    def valid_geojson?(geojson)
       return false unless geojson.is_a?(Hash)
 
-      geojson.dig("geometry", "coordinates").is_a?(Array)
+      if geojson["type"] == "FeatureCollection"
+        valid_feature_collection?(geojson)
+      elsif geojson["type"] == "Feature"
+        valid_feature?(geojson)
+      else
+        valid_geometry?(geojson)
+      end
+    end
+
+    def valid_feature_collection?(geojson)
+      return false unless geojson["features"].is_a?(Array)
+
+      geojson["features"].all? { |feature| valid_feature?(feature) }
+    end
+
+    def valid_feature?(feature)
+      feature["type"] == "Feature" && valid_geometry?(feature["geometry"])
+    end
+
+    def valid_geometry?(geometry)
+      geometry.is_a?(Hash) && valid_geometry_types.include?(geometry["type"])
+    end
+
+    def valid_geometry_types
+      [
+        "Point", "LineString", "Polygon", "MultiPoint", "MultiLineString", "MultiPolygon",
+        "GeometryCollection"
+      ]
+    end
+
+    def valid_coordinates?(geojson)
+      if geojson["type"] == "FeatureCollection"
+        geojson["features"].all? { |feature| valid_coordinates?(feature) }
+      elsif geojson["type"] == "Feature"
+        valid_geometry_coordinates?(geojson["geometry"])
+      else
+        valid_geometry_coordinates?(geojson)
+      end
+    end
+
+    def valid_geometry_coordinates?(geometry)
+      if geometry["type"] == "GeometryCollection"
+        geometries = geometry["geometries"]
+
+        return geometries.is_a?(Array) && geometries.all? { |geom| valid_geometry_coordinates?(geom) }
+      end
+
+      coordinates = geometry["coordinates"]
+
+      return false unless coordinates.is_a?(Array)
+
+      case geometry["type"]
+      when "Point"
+        valid_wgs84_coordinates?(coordinates)
+      when "LineString", "MultiPoint"
+        coordinates.all? { |coordinates| valid_wgs84_coordinates?(coordinates) }
+      when "Polygon", "MultiLineString"
+        valid_polygon_coordinates?(coordinates)
+      when "MultiPolygon"
+        coordinates.all? do |polygon_coordinates|
+          valid_polygon_coordinates?(polygon_coordinates)
+        end
+      else
+        false
+      end
+    end
+
+    def valid_wgs84_coordinates?(coordinates)
+      return false unless coordinates.is_a?(Array) && coordinates.size == 2
+
+      longitude, latitude = coordinates
+      (-180.0..180.0).include?(longitude) && (-90.0..90.0).include?(latitude)
+    end
+
+    def valid_polygon_coordinates?(polygon_coordinates)
+      polygon_coordinates.all? do |ring|
+        ring.all? { |coordinates| valid_wgs84_coordinates?(coordinates) }
+      end
     end
 end