Allow negative cost_per_unit for geofences

lib/teslamate/locations/geo_fence.ex

@@ -34,7 +34,6 @@ defmodule TeslaMate.Locations.GeoFence do
     ])
     |> validate_required([:name, :latitude, :longitude, :radius])
     |> validate_number(:radius, greater_than: 0, less_than: 5000)
-    |> validate_number(:cost_per_unit, greater_than_or_equal_to: 0)
     |> validate_number(:session_fee, greater_than_or_equal_to: 0)
   end
 end

lib/teslamate_web/live/geofence_live/form.html.leex

@@ -68,7 +68,7 @@
         </p>
         <p class="control is-expanded">
           <%= text_input f, :cost_per_unit, class: "input",
-                             type: :number, inputmode: :decimal, min: 0.0, step: 0.0001,
+                             type: :number, inputmode: :decimal, step: 0.0001,
                              placeholder: "0.00" %>
         </p>
         <%= if @show_errors do %>

test/teslamate/locations/geofences_test.exs

@@ -29,7 +29,6 @@ defmodule TeslaMate.LocationsGeofencesTest do
     longitude: nil,
     radius: nil,
     billing_type: :per_hour,
-    cost_per_unit: -0.01,
     session_fee: -0.01
   }
 
@@ -67,7 +66,6 @@ defmodule TeslaMate.LocationsGeofencesTest do
                name: ["can't be blank"],
                radius: ["can't be blank"],
                billing_type: ["is invalid"],
-               cost_per_unit: ["must be greater than or equal to 0"],
                session_fee: ["must be greater than or equal to 0"]
              }
 

test/teslamate/log/log_charging_test.exs

@@ -543,6 +543,33 @@ defmodule TeslaMate.LogChargingTest do
       assert cproc.cost == Decimal.new("0.00")
     end
 
+    test "cost per unit can be negative" do
+      car = car_fixture()
+
+      assert %GeoFence{id: id} =
+               geofence_fixture(%{
+                 latitude: 50.1121,
+                 longitude: 11.597,
+                 radius: 50,
+                 cost_per_unit: -0.15,
+                 session_fee: 0.0
+               })
+
+      assert {:ok, cproc} =
+               log_charging_process(charges_fixture(:phases_nil),
+                 car: car,
+                 attrs: %{
+                   date: DateTime.utc_now(),
+                   latitude: 50.112198,
+                   longitude: 11.597669
+                 }
+               )
+
+      assert cproc.charge_energy_added == Decimal.from_float(12.77)
+      assert cproc.charge_energy_used == Decimal.from_float(12.46)
+      assert cproc.cost == Decimal.new("-1.92")
+    end
+
     test "sets charge cost to zero if free supercharging is enabled" do
       alias TeslaMate.Settings