Store GeoJSON with Fundamentals types

Use the geospatial types from @cratis/fundamentals/geospatial when a MongoDB read model stores locations, routes, or areas. MongoDocumentCodec writes their geometry as GeoJSON without changing driver-wide BSON serialization.

Point: one location

Declare @field(Point) on the model. Longitude comes first, then latitude:

import { field } from '@cratis/fundamentals';
import { Point } from '@cratis/fundamentals/geospatial';
import { key } from '@cratis/arc.core';

class Place {
    @field(String) @key() id!: string;
    @field(Point) location!: Point;
}

const place = Object.assign(new Place(), { id: 'one', location: new Point(10, 20) });
// collection.codec.serialize(place).location -> { type: 'Point', coordinates: [10, 20] }

MongoDB can index the stored location field with a 2dsphere index. Creating indexes and composing $near filters are application responsibilities; the Fundamentals Point is not a driver GeoJSON filter-builder argument.

LineString: a route

A LineString holds two or more Points. The codec writes { type: 'LineString', coordinates: [[10, 20], [30, 40]] } for:

import { LineString, Point } from '@cratis/fundamentals/geospatial';

const route = new LineString([new Point(10, 20), new Point(30, 40)]);

Declare the field with @field(LineString). Typed reads restore LineString and Point instances, not plain arrays.

Polygon: an area, optionally with holes

A polygon stores the outer shell first and then its interior rings. Each LinearRing needs at least four points; repeat the first point as the last:

import { LinearRing, Point, Polygon } from '@cratis/fundamentals/geospatial';

const shell = new LinearRing([
    new Point(10, 20), new Point(30, 20), new Point(30, 40), new Point(10, 20)
]);
const area = new Polygon(shell);

Declare @field(Polygon) on the model. The BSON field contains { type: 'Polygon', coordinates: [/* shell coordinates, then holes */] }; reads reconstruct Polygon and its LinearRings. The codec rejects an unclosed ring, non-finite coordinates, a mismatched GeoJSON type, or missing coordinates rather than returning a misleading geometry. It does not enforce winding order, non-intersection, or MongoDB’s full spatial-index rules. Validate domain geometry before writing, and use stored MongoDB field names in your own spatial filters. See serializers for the other model types and naming policies for stored names.