From 0ea4fd7a9c3be48bdcdf61e60996ce2ebe46c5c3 Mon Sep 17 00:00:00 2001
From: Anton Maminov <anton.linux@gmail.com>
Date: Thu, 11 Apr 2024 15:24:36 +0300
Subject: [PATCH] add geocrystal/geojson and to_geojson methods

---
 shard.yml                |  2 ++
 spec/geo/coord_spec.cr   |  8 ++++++++
 spec/geo/polygon_spec.cr | 18 ++++++++++++++++++
 src/geo.cr               |  1 +
 src/geo/coord.cr         |  4 ++++
 src/geo/polygon.cr       |  6 ++++++
 6 files changed, 39 insertions(+)

diff --git a/shard.yml b/shard.yml
index a55b005..9c2242b 100644
--- a/shard.yml
+++ b/shard.yml
@@ -16,6 +16,8 @@ dependencies:
     github: geocrystal/geo_bearing
   ring_area:
     github: geocrystal/ring_area
+  geojson:
+    github: geocrystal/geojson
 
 development_dependencies:
   ameba:
diff --git a/spec/geo/coord_spec.cr b/spec/geo/coord_spec.cr
index e9bf473..a95c5db 100644
--- a/spec/geo/coord_spec.cr
+++ b/spec/geo/coord_spec.cr
@@ -103,6 +103,14 @@ describe Geo::Coord do
     end
   end
 
+  describe "#to_geojson" do
+    coord = Geo::Coord.new(-15, 125)
+
+    geojson = coord.to_geojson
+
+    geojson.should be_a(GeoJSON::Coordinates)
+  end
+
   describe "comparisons" do
     describe "equality" do
       pos1 = Geo::Coord.new(45.3142533036254, -93.47527313511819)
diff --git a/spec/geo/polygon_spec.cr b/spec/geo/polygon_spec.cr
index 73b213c..94c88d0 100644
--- a/spec/geo/polygon_spec.cr
+++ b/spec/geo/polygon_spec.cr
@@ -100,6 +100,24 @@ describe Geo::Polygon do
     it { polygon.area.should eq(7748891609977.457) }
   end
 
+  describe "#to_geojson" do
+    coords = [
+      Geo::Coord.new(-15, 125),
+      Geo::Coord.new(-22, 113),
+      Geo::Coord.new(-37, 117),
+      Geo::Coord.new(-33, 130),
+      Geo::Coord.new(-39, 148),
+      Geo::Coord.new(-27, 154),
+      Geo::Coord.new(-15, 144),
+      Geo::Coord.new(-15, 125),
+    ]
+
+    polygon = Geo::Polygon.new(coords)
+    geojson = polygon.to_geojson
+
+    geojson.should be_a(GeoJSON::Polygon)
+  end
+
   describe "comparisons" do
     describe "equality" do
       polygon1 = Geo::Polygon.new([pos1, pos2])
diff --git a/src/geo.cr b/src/geo.cr
index 104323b..76a70d5 100644
--- a/src/geo.cr
+++ b/src/geo.cr
@@ -3,6 +3,7 @@ require "geohash"
 require "geo_bearing"
 require "haversine"
 require "ring_area"
+require "geojson"
 require "./geo/utils"
 require "./geo/coord"
 require "./geo/polygon"
diff --git a/src/geo/coord.cr b/src/geo/coord.cr
index e7e14f3..9d9aa62 100644
--- a/src/geo/coord.cr
+++ b/src/geo/coord.cr
@@ -156,6 +156,10 @@ module Geo
       Geohash.encode(lat.to_f, lng.to_f, precision)
     end
 
+    def to_geojson : GeoJSON::Coordinates
+      GeoJSON::Coordinates.new(lng.to_f64, lat.to_f64)
+    end
+
     # Returns a string representing coordinates.
     #
     # ```
diff --git a/src/geo/polygon.cr b/src/geo/polygon.cr
index fd54eb6..0a7ea4a 100644
--- a/src/geo/polygon.cr
+++ b/src/geo/polygon.cr
@@ -100,6 +100,12 @@ module Geo
       size == other.size
     end
 
+    def to_geojson : GeoJSON::Polygon
+      coordinates = @coords.map { |coord| GeoJSON::Coordinates.new(coord.lng.to_f64, coord.lat.to_f64) }
+
+      GeoJSON::Polygon.new([coordinates])
+    end
+
     private def calculate_centroid : Geo::Coord
       centroid_lat = 0.0
       centroid_lng = 0.0