circe-geojson.scala

import io.circe._
import io.circe.generic.auto._
import io.circe.parser._

val jsonPoint = "{ \"type\": \"Point\", \"coordinates\": [100.0, 0.0] }"
val jsonLineString = "{ \"type\": \"LineString\",\n    \"coordinates\": [ [100.0, 0.0], [101.0, 1.0] ]\n    }"
val jsonPolygon = "{ \"type\": \"Polygon\",\n    \"coordinates\": [\n      [ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ]\n      ]\n   }"
val jsonPolygonWithHoles = "{ \"type\": \"Polygon\",\n    \"coordinates\": [\n      [ [100.0, 0.0], [101.0, 0.0], [101.0, 1.0], [100.0, 1.0], [100.0, 0.0] ],\n      [ [100.2, 0.2], [100.8, 0.2], [100.8, 0.8], [100.2, 0.8], [100.2, 0.2] ]\n      ]\n   }"
val jsonGC = "{ \"type\": \"GeometryCollection\",\n    \"geometries\": [\n      { \"type\": \"Point\",\n        \"coordinates\": [100.0, 0.0]\n        },\n      { \"type\": \"LineString\",\n        \"coordinates\": [ [101.0, 0.0], [102.0, 1.0] ]\n        }\n    ]\n  }"


case class Coordinates(x: Double, y: Double)
object Coordinates {
  implicit val decoder: Decoder[Coordinates] =
    Decoder[(Double, Double)].map(p => Coordinates(p._1, p._2))
}


sealed trait Geometry
case class Point(coordinates: Coordinates) extends Geometry
case class LineString(coordinates: List[Coordinates]) extends Geometry
case class MultiPoint(coordinates: List[Coordinates]) extends Geometry
case class MultiLineString(coordinates: List[List[Coordinates]]) extends Geometry
case class Polygon(coordinates: List[List[Coordinates]]) extends Geometry
case class MultiPolygon(coordinates: List[List[List[Coordinates]]]) extends Geometry
case class GeometryCollection(geometries: List[Geometry]) extends Geometry

object Geometry {
  implicit val decoder: Decoder[Geometry] = Decoder.instance { c =>
    c.downField("type").as[String].map(_.toLowerCase).flatMap {
      case "point"              => c.as[Point]
      case "linestring"         => c.as[LineString]
      case "multipoint"         => c.as[MultiPoint]
      case "multilinestring"    => c.as[MultiLineString]
      case "polygon"            => c.as[Polygon]
      case "multipolygon"       => c.as[MultiPolygon]
      case "geometrycollection" => c.as[GeometryCollection]
    }
  }
}

decode[Geometry](jsonPoint)
decode[Geometry](jsonLineString)
decode[Geometry](jsonPolygon)
decode[Geometry](jsonPolygonWithHoles)
decode[Geometry](jsonGC)