[ongoing] chain invoice records

app/models/invoice.rb

@@ -14,7 +14,7 @@ class Invoice < ActiveRecord::Base
 
   has_one :avoir, class_name: 'Invoice', foreign_key: :invoice_id, dependent: :destroy
 
-  after_create :update_reference
+  after_create :update_reference, :chain_record
   after_commit :generate_and_send_invoice, on: [:create], if: :persisted?
 
   validates_with ClosedPeriodValidator
@@ -211,6 +211,17 @@ class Invoice < ActiveRecord::Base
     total - (wallet_amount || 0)
   end
 
+  def chain_record
+    sha256 = Digest::SHA256.new
+
+    previous = Invoice.where(created_at: Invoice.select('MAX(created_at)')).limit(1).first
+
+    self.footprint = sha256.hexdigest "#{id}#{invoice_id}#{invoiced_type}#{stp_invoice_id}#{total}#{created_at}#{updated_at}" \
+                                      "#{user_id}#{reference}#{avoir_mode}#{avoir_date}#{invoice_id}#{type}" \
+                                      "#{subscription_to_expire}#{description}#{wallet_amount}#{wallet_transaction_id}" \
+                                      "#{coupon_id}#{previous ? previous.footprint : ''}"
+  end
+
   private
 
   def generate_and_send_invoice

db/migrate/20190211124135_add_footprint_to_invoice.rb

@@ -0,0 +1,5 @@
+class AddFootprintToInvoice < ActiveRecord::Migration
+  def change
+    add_column :invoices, :footprint, :string
+  end
+end

db/migrate/20190211124726_add_footprint_to_invoice_item.rb

@@ -0,0 +1,5 @@
+class AddFootprintToInvoiceItem < ActiveRecord::Migration
+  def change
+    add_column :invoice_items, :footprint, :string
+  end
+end