feat(parse): accept gzip-encoded values for VehiclePositions

apps/parse/lib/parse/vehicle_positions.ex

@@ -9,16 +9,30 @@ defmodule Parse.VehiclePositions do
   alias Parse.Realtime.FeedMessage
   import Parse.Helpers
 
+  def parse(<<31, 139, _::binary>> = blob) do
+    # gzip encoded
+    blob
+    |> :zlib.gunzip()
+    |> parse
+  end
+
   def parse("{" <> _ = blob) do
     Parse.VehiclePositionsJson.parse(blob)
   end
 
   def parse(blob) do
-    blob
-    |> FeedMessage.decode()
-    |> (fn message -> message.entity end).()
-    |> Stream.map(fn entity -> entity.vehicle end)
-    |> Stream.map(&parse_vehicle_update/1)
+    decoded = FeedMessage.decode(blob)
+
+    entities =
+      decoded.entity
+      |> Stream.map(fn entity -> entity.vehicle end)
+      |> Stream.map(&parse_vehicle_update/1)
+
+    if decoded.header.incrementality == :DIFFERENTIAL do
+      {:partial, entities}
+    else
+      entities
+    end
   end
 
   def parse_vehicle_update(update) do

apps/parse/lib/parse/vehicle_positions_json.ex

@@ -7,10 +7,18 @@ defmodule Parse.VehiclePositionsJson do
   alias Model.Vehicle
 
   def parse(body) do
-    body
-    |> Jason.decode!(strings: :copy)
-    |> Map.get("entity")
-    |> Enum.flat_map(&parse_entity/1)
+    decoded = Jason.decode!(body, strings: :copy)
+
+    entities =
+      decoded
+      |> Map.get("entity")
+      |> Enum.flat_map(&parse_entity/1)
+
+    if decoded["header"]["incrementality"] in ["DIFFERENTIAL", 1] do
+      {:partial, entities}
+    else
+      entities
+    end
   end
 
   def parse_entity(
@@ -109,6 +117,10 @@ defmodule Parse.VehiclePositionsJson do
     Parse.Timezone.unix_to_local(timestamp)
   end
 
+  defp unix_to_local(timestamp) when is_float(timestamp) do
+    Parse.Timezone.unix_to_local(trunc(timestamp))
+  end
+
   defp unix_to_local(nil) do
     DateTime.utc_now()
   end

apps/parse/test/parse/vehicle_positions_test.exs

@@ -108,6 +108,12 @@ defmodule Parse.VehiclePositionsTest do
       actual = parse(body)
       assert actual == expected
     end
+
+    test "can parse gzip-encoded JSON" do
+      body = :zlib.gzip(Jason.encode!(%{entity: [@vehicle]}))
+      actual = parse(body)
+      assert [_] = actual
+    end
   end
 
   describe "parse_vehicle_update/1" do