Add `WayCostCollectionJSONSerializer`

A JSON serialiser for a collection of `WayCost`s. This will be used to
store `WayCost`s for a `Chouette::Route` in the `Route#costs` JSON
field.

Refs #6095

2 files changed, 53 insertions, 0 deletions

diff --git a/lib/way_cost_collection_json_serializer.rb b/lib/way_cost_collection_json_serializer.rb
new file mode 100644
index 000000000..191871cca
--- /dev/null
+++ b/lib/way_cost_collection_json_serializer.rb
@@ -0,0 +1,16 @@
+class WayCostCollectionJSONSerializer
+  def self.dump(way_costs)
+    return if way_costs.nil?
+
+    costs_by_id = {}
+
+    way_costs.each do |way_cost|
+      costs_by_id[way_cost.id] = {
+        distance: way_cost.distance,
+        time: way_cost.time
+      }
+    end
+
+    JSON.dump(costs_by_id)
+  end
+end
diff --git a/spec/lib/way_cost_collection_json_serializer_spec.rb b/spec/lib/way_cost_collection_json_serializer_spec.rb
new file mode 100644
index 000000000..22faf88d3
--- /dev/null
+++ b/spec/lib/way_cost_collection_json_serializer_spec.rb
@@ -0,0 +1,37 @@
+RSpec.describe WayCostCollectionJSONSerializer do
+  describe ".dump" do
+    it "creates a JSON hash of hashed WayCost attributes" do
+      way_costs = [
+        WayCost.new(
+          departure: Geokit::LatLng.new(48.85086, 2.36143),
+          arrival: Geokit::LatLng.new(47.91231, 1.87606),
+          distance: 1234,
+          time: 99,
+          id: '1-2'
+        ),
+        WayCost.new(
+          departure: Geokit::LatLng.new(47.91231, 1.87606),
+          arrival: Geokit::LatLng.new(52.50867, 13.42879),
+          distance: 5678,
+          time: 999,
+          id: '2-3'
+        )
+      ]
+
+      expect(
+        WayCostCollectionJSONSerializer.dump(way_costs)
+      ).to eq(<<-JSON.delete(" \n"))
+        {
+          "1-2": {
+            "distance": 1234,
+            "time": 99
+          },
+          "2-3": {
+            "distance": 5678,
+            "time": 999
+          }
+        }
+      JSON
+    end
+  end
+end