Measurement - envelope

geojson/src/commonMain/kotlin/io/github/dellisd/spatialk/geojson/GeoJson.kt

@@ -5,7 +5,7 @@ package io.github.dellisd.spatialk.geojson
  *
  * @property bbox An optional bounding box used to represent the limits of the object's geometry.
  */
-interface GeoJson {
+sealed interface GeoJson {
     val bbox: BoundingBox?
 
     /**

turf/src/commonMain/kotlin/io/github/dellisd/spatialk/turf/Measurement.kt

@@ -6,6 +6,7 @@ package io.github.dellisd.spatialk.turf
 import io.github.dellisd.spatialk.geojson.BoundingBox
 import io.github.dellisd.spatialk.geojson.Feature
 import io.github.dellisd.spatialk.geojson.FeatureCollection
+import io.github.dellisd.spatialk.geojson.GeoJson
 import io.github.dellisd.spatialk.geojson.Geometry
 import io.github.dellisd.spatialk.geojson.GeometryCollection
 import io.github.dellisd.spatialk.geojson.LineString
@@ -652,3 +653,25 @@ fun greatCircle(start: Position, end: Position, pointCount: Int = 100, antimerid
     }
 }
 
+
+/**
+ * Takes any [GeoJson] and returns a [Feature] containing a rectangular [Polygon] that encompasses all vertices.
+ * @param geoJson input containing any coordinates
+ * @return a rectangular [Polygon] feature that encompasses all vertices
+ */
+@ExperimentalTurfApi
+fun envelope(geoJson: GeoJson): Feature {
+    val coordinates = when (geoJson) {
+        is Feature -> geoJson.coordAll()
+        is FeatureCollection -> geoJson.coordAll()
+        is GeometryCollection -> geoJson.coordAll()
+        is Geometry -> geoJson.coordAll()
+    }.orEmpty()
+
+    val bbox = geoJson.bbox ?: computeBbox(coordinates)
+
+    return Feature(
+        geometry = bboxPolygon(bbox),
+        bbox = bbox
+    )
+}

turf/src/commonTest/kotlin/io/github/dellisd/spatialk/turf/TurfMeasurementTest.kt

@@ -3,13 +3,16 @@
 package io.github.dellisd.spatialk.turf
 
 import io.github.dellisd.spatialk.geojson.BoundingBox
+import io.github.dellisd.spatialk.geojson.Feature
 import io.github.dellisd.spatialk.geojson.LineString
 import io.github.dellisd.spatialk.geojson.MultiLineString
-import io.github.dellisd.spatialk.geojson.Feature
 import io.github.dellisd.spatialk.geojson.Point
 import io.github.dellisd.spatialk.geojson.Polygon
 import io.github.dellisd.spatialk.geojson.Position
+import io.github.dellisd.spatialk.geojson.dsl.featureCollection
 import io.github.dellisd.spatialk.geojson.dsl.geometryCollection
+import io.github.dellisd.spatialk.geojson.dsl.lineString
+import io.github.dellisd.spatialk.geojson.dsl.point
 import io.github.dellisd.spatialk.geojson.dsl.polygon
 import io.github.dellisd.spatialk.turf.utils.assertDoubleEquals
 import io.github.dellisd.spatialk.turf.utils.readResource
@@ -186,4 +189,54 @@ class TurfMeasurementTest {
             greatCircle(start, antipodal)
         }
     }
+
+    @Test
+    fun envelopeProcessesFeatureCollection() {
+        val fc = featureCollection {
+            feature(
+                geometry = point(102.0, 0.5)
+            )
+            feature(
+                geometry = lineString {
+                    point(102.0, -10.0)
+                    point(103.0, 1.0)
+                    point(104.0, 0.0)
+                    point(130.0, 4.0)
+                }
+            )
+            feature(
+                geometry = polygon {
+                    ring {
+                        point(102.0, -10.0)
+                        point(103.0, 1.0)
+                        point(104.0, 0.0)
+                        point(130.0, 4.0)
+                        point(20.0, 0.0)
+                        point(101.0, 0.0)
+                        point(101.0, 1.0)
+                        point(100.0, 1.0)
+                        point(100.0, 0.0)
+                    }
+                }
+            )
+        }
+
+        val enveloped = envelope(fc)
+
+        assertIs<Polygon>(enveloped.geometry, "geometry type should be Polygon")
+        assertEquals(
+            listOf(
+                listOf(
+                    Position(20.0, -10.0),
+                    Position(130.0, -10.0),
+                    Position(130.0, 4.0),
+                    Position(20.0, 4.0),
+                    Position(20.0, -10.0),
+                )
+            ),
+            (enveloped.geometry as Polygon).coordinates,
+            "positions should be correct"
+        )
+    }
+
 }