Add CSV download of H2 curves

app/controllers/api/v3/curves_controller.rb

@@ -53,6 +53,16 @@ def household_heat_curves
         end
       end
 
+      # Downloads the total demand and supply for hydrogen, with additional
+      # columns for the storage demand and supply.
+      def hydrogen
+        presenter = Api::V3::HydrogenCSVPresenter.new(scenario.gql.future_graph)
+
+        send_csv('hydrogen') do |csv|
+          presenter.to_csv_rows.each { |row| csv << row }
+        end
+      end
+
       private
 
       def merit_required

app/models/api/v3/hydrogen_csv_presenter.rb

@@ -0,0 +1,63 @@
+module Api
+  module V3
+    # Creates CSV rows describing hydrogen production.
+    class HydrogenCSVPresenter
+      def initialize(graph)
+        @graph = graph
+      end
+
+      # Public: Creates an array of rows for a CSV file containing the loads of
+      # hydrogen producers and consumers.
+      #
+      # Returns an array of arrays.
+      def to_csv_rows
+        # Empty CSV if time-resolved calculations are not enabled.
+        unless @graph.plugin(:time_resolve)&.hydrogen
+          return [['Merit order and time-resolved calculation are not ' \
+                   'enabled for this scenario']]
+        end
+
+        [*producer_columns, *consumer_columns].transpose
+      end
+
+      private
+
+      # Internal: Data about hydrogen production.
+      def producer_columns
+        converters_of_type(:producer, :import, :storage).map do |converter|
+          column_from_converter(converter, :output)
+        end
+      end
+
+      # Internal: Data about consumption production.
+      def consumer_columns
+        converters_of_type(:consumer, :export, :storage).map do |converter|
+          column_from_converter(converter, :input)
+        end
+      end
+
+      # Internal: Creates a column representing data for a converter in a
+      # direction.
+      def column_from_converter(converter, direction)
+        loads = converter.converter_api
+          .public_send("hydrogen_#{direction}_curve").map { |val| val.round(2) }
+
+        ["#{converter.key}.#{direction}", *loads]
+      end
+
+      def converters_of_type(*types)
+        types.flat_map { |type| converters[type] }.sort_by(&:key)
+      end
+
+      def converters
+        @converters ||= @graph.converters.select(&:hydrogen)
+          .each_with_object({}) do |converter, data|
+            next unless converter.hydrogen
+
+            data[converter.hydrogen.type] ||= []
+            data[converter.hydrogen.type].push(converter)
+          end
+      end
+    end
+  end
+end

config/routes.rb

@@ -44,6 +44,10 @@
           to: 'curves#household_heat_curves',
           as: :curves_household_heat_download
 
+        get 'curves/hydrogen',
+          to: 'curves#hydrogen',
+          as: :curves_hydrogen_download
+
         # Old paths for Merit downloads.
         get 'merit/loads', to: redirect('api/v3/scenarios/%{scenario_id}/curves/loads')
         get 'merit/price', to: redirect('api/v3/scenarios/%{scenario_id}/curves/price')