Added route and serializer for fetching output curves in bulk

app/controllers/api/v3/export_controller.rb

@@ -71,6 +71,26 @@ def costs_parameters
         send_csv(CostsParametersSerializer.new(@scenario), 'costs_parameters.%d.csv')
       end
 
+      # GET /api/v3/scenarios/:id/bulk_output_curves
+      #
+      # Returns a single CSV file with specified output curves as columns.
+      # Query parameter 'curve_types' specifies which curves to include (comma-separated).
+      def bulk_output_curves
+        curve_types = params[:curve_types]&.split(',')&.map(&:strip)
+
+        if curve_types.blank?
+          render json: { error: 'curve_types parameter is required' }, status: :bad_request
+          return
+        end
+
+        serializer = OutputCurvesBulkSerializer.new(@scenario, curve_types)
+        send_data(
+          serializer.as_csv,
+          type: 'text/csv',
+          filename: "output_curves.#{@scenario.id}.csv"
+        )
+      end
+
       private
 
       def send_csv(serializer, filename_template)

app/serializers/output_curves_bulk_serializer.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# Serializes specified output curves for a scenario as a single CSV with each curve as a column.
+class OutputCurvesBulkSerializer
+
+  def initialize(scenario, curve_types)
+    @scenario = scenario
+    @curve_types = curve_types || []
+  end
+
+  def as_csv
+    return empty_csv if @curve_types.empty?
+
+    curves = {}
+    @curve_types.each do |curve_type|
+      csv = QueryCurveCsvSerializer.new(@scenario, curve_type).as_csv
+      lines = csv.lines.map(&:strip).reject(&:empty?)
+      lines.shift if lines.first && lines.first.match?(/[^\d.\-eE]/)
+      curves[curve_type] = lines
+    rescue
+      curves[curve_type] = []
+    end
+
+    max_len = curves.values.map(&:length).max || 0
+    require 'csv'
+    CSV.generate do |csv|
+      csv << curves.keys
+      (0...max_len).each do |i|
+        csv << curves.keys.map { |k| curves[k][i] }
+      end
+    end
+  end
+
+  private
+
+  def empty_csv
+    require 'csv'
+    CSV.generate { |csv| csv << [] }
+  end
+end

config/routes.rb

@@ -26,6 +26,7 @@
           get :costs_parameters,       to: 'export#costs_parameters'
           get :sankey,                 to: 'export#sankey'
           get :storage_parameters,     to: 'export#storage_parameters'
+          get :bulk_output_curves,     to: 'export#bulk_output_curves'
           get :merit
           get :dump
           put :dashboard
@@ -80,7 +81,6 @@
           controller: :user_sortables, sortable_type: :space_heating
 
         resources :custom_curves, only: %i[index]
-
         get    'custom_curves/*id', to: 'custom_curves#show'
         put    'custom_curves/*id', to: 'custom_curves#update'
         delete 'custom_curves/*id', to: 'custom_curves#destroy'