Display default xero invoice dates

fixes #682

* pre-fill the invoice_date and due_date in the xero report generation form
* increase the default period between invoice_date and due_date to 1 month in
XeroInvoiceReport

app/controllers/spree/admin/reports_controller_decorator.rb

@@ -244,7 +244,9 @@ Spree::Admin::ReportsController.class_eval do
   def xero_invoices
     if request.get?
       params[:q] ||= {}
-      params[:q][:completed_at_gt] = Time.zone.now.beginning_of_month
+      params[:q][:completed_at_gt] = Time.zone.today.beginning_of_month
+      params[:invoice_date] = Time.zone.today
+      params[:due_date] = Time.zone.today + 1.month
     end
     @distributors = Enterprise.is_distributor.managed_by(spree_current_user)
     @order_cycles = OrderCycle.active_or_complete.accessible_by(spree_current_user).order('orders_close_at DESC')

lib/open_food_network/xero_invoices_report.rb

@@ -6,8 +6,8 @@ module OpenFoodNetwork
       @opts = opts.
               reject { |k, v| v.blank? }.
               reverse_merge({report_type: 'summary',
-                             invoice_date: Date.today,
-                             due_date: 2.weeks.from_now.to_date,
+                             invoice_date: Time.zone.today,
+                             due_date: Time.zone.today + 1.month,
                              account_code: 'food sales'})
     end
 

spec/lib/open_food_network/xero_invoices_report_spec.rb

@@ -11,7 +11,7 @@ module OpenFoodNetwork
 
       it "uses defaults when blank params are passed" do
         report.instance_variable_get(:@opts).should == {invoice_date: Date.civil(2015, 5, 5),
-                                                        due_date: Date.civil(2015, 5, 19),
+                                                        due_date: Date.civil(2015, 6, 5),
                                                         account_code: 'food sales',
                                                         report_type: 'summary'}
       end