Functional inputs serialisation to csv

app/controllers/api/v3/inputs_controller.rb

@@ -6,6 +6,7 @@ class InputsController < ::Api::V3::BaseController
       before_action do
         @scenario = Scenario.find(params[:scenario_id])
         authorize!(:read, @scenario)
+        set_default_format
       end
 
       # GET /api/v3/inputs
@@ -17,11 +18,33 @@ class InputsController < ::Api::V3::BaseController
       def index
         extras = ActiveModel::Type::Boolean.new.cast(params[:include_extras])
 
-        render json: InputSerializer.collection(
-          Input.all,
-          @scenario,
-          **serializer_args(extra_attributes: extras)
-        )
+        respond_to do |format|
+          format.json do
+            render json: InputSerializer.collection(
+              Input.all,
+              @scenario,
+              **serializer_args(extra_attributes: extras)
+            )
+          end
+
+          format.csv do
+            csv_data = CSV.generate(headers: true) do |csv|
+              csv << ["Key", "Min", "Max", "Default", "User value", "Unit", "Share Group"]
+              Input.all.each do |input|
+                serializer = InputSerializer.serializer_for(
+                  input,
+                  @scenario,
+                  **serializer_args(extra_attributes: extras)
+                )
+                csv << serializer.to_csv_row
+              end
+            end
+
+            send_data csv_data,
+                      filename: "scenario_#{@scenario.id}_inputs.csv",
+                      type: "text/csv"
+          end
+        end
       end
 
       # GET /api/v3/inputs/:id
@@ -77,6 +100,10 @@ def serializer_args(extra_attributes:)
           extra_attributes:
         }
       end
+
+      def set_default_format
+        request.format = :json unless params[:format]
+      end
     end
   end
 end

app/serializers/input_serializer.rb

@@ -124,6 +124,19 @@ def as_json(*)
     json
   end
 
+  def to_csv_row
+    json = as_json.with_indifferent_access
+    [
+      @input.key,               # Key
+      json[:min] || "",         # Min Value
+      json[:max] || "",         # Max Value
+      json[:default] || "",     # Default Value
+      json[:user] || "",        # User Value
+      json[:unit] || "",        # Unit
+      json[:share_group] || ""  # Share Group
+    ]
+  end
+
   # A simple wrapper around Scenario which converts user and balanced values
   # to an indifferent-access hash. Prevents creating new copies of these
   # hashes for each and every input being presented.