allow to set default field values via api

app/controllers/api/submissions_controller.rb

@@ -2,6 +2,9 @@
 
 module Api
   class SubmissionsController < ApiBaseController
+    UnknownFieldName = Class.new(StandardError)
+    UnknownSubmitterName = Class.new(StandardError)
+
     def create
       template = current_account.templates.find(params[:template_id])
 
@@ -13,28 +16,65 @@ module Api
                                          send_email: params[:send_email] != 'false',
                                          emails: params[:emails] || params[:email])
         else
+          submissions_attrs = normalize_submissions_params!(submissions_params[:submission], template)
+
           Submissions.create_from_submitters(template:,
                                              user: current_user,
                                              source: :api,
                                              send_email: params[:send_email] != 'false',
-                                             submissions_attrs: submissions_params[:submission])
+                                             submissions_attrs:)
         end
 
       submitters = submissions.flat_map(&:submitters)
 
-      if params[:send_email] != 'false'
-        submitters.each do |submitter|
-          SubmitterMailer.invitation_email(submitter, message: params[:message]).deliver_later!
-        end
-      end
+      send_invitation_emails(submitters) if params[:send_email] != 'false'
 
       render json: submitters
+    rescue UnknownFieldName, UnknownSubmitterName => e
+      render json: { error: e.message }, status: :unprocessable_entity
     end
 
     private
 
+    def send_invitation_emails(submitters)
+      submitters.each do |submitter|
+        SubmitterMailer.invitation_email(submitter, message: params[:message]).deliver_later!
+      end
+    end
+
     def submissions_params
-      params.permit(submission: [{ submitters: [%i[uuid name email]] }])
+      params.permit(submission: [{ submitters: [[:uuid, :name, :email, { values: {} }]] }])
+    end
+
+    def normalize_submissions_params!(submissions_params, template)
+      submissions_params.each do |submission|
+        submission[:submitters].each_with_index do |submitter, index|
+          next if submitter[:values].blank?
+
+          submitter[:values] =
+            normalize_submitter_values(template,
+                                       submitter[:values], submitter[:name] || template.submitters[index]['name'])
+        end
+      end
+
+      submissions_params
+    end
+
+    def normalize_submitter_values(template, values, submitter_name)
+      submitter =
+        template.submitters.find { |e| e['name'] == submitter_name } ||
+        raise(UnknownSubmitterName, "Unknown submitter: #{submitter_name}")
+
+      fields = template.fields.select { |e| e['submitter_uuid'] == submitter['uuid'] }
+
+      fields_uuid_index = fields.index_by { |e| e['uuid'] }
+      fields_name_index = fields.index_by { |e| e['name'] }
+
+      values.transform_keys do |key|
+        next key if fields_uuid_index[key].present?
+
+        fields_name_index[key]&.dig('uuid') || raise(UnknownFieldName, "Unknown field: #{key}")
+      end
     end
   end
 end