Add resilience against credit notes being created manually for progre…

…ssive billing invoices

app/services/credit_notes/validate_item_service.rb

@@ -53,9 +53,9 @@ def valid_fee?
       false
     end
 
-    # NOTE: Check if item amount is positive
+    # NOTE: Check if item amount is not negative
     def valid_item_amount?
-      return true if item.amount_cents.positive?
+      return true unless item.amount_cents.negative?
 
       add_error(field: :amount_cents, error_code: 'invalid_value')
     end

app/services/credits/progressive_billing_service.rb

@@ -23,7 +23,7 @@ def call
 
         total_charges_amount = invoice.fees.charge.where(subscription: subscription).sum(:amount_cents)
 
-        amount_to_credit = progressive_billing_invoice.fees_amount_cents
+        amount_to_credit = progressive_billed_result.amount_to_credit
 
         if amount_to_credit > total_charges_amount
           CreditNotes::CreateFromProgressiveBillingInvoice.call(

app/services/subscriptions/progressive_billed_amount.rb

@@ -23,8 +23,18 @@ def call
         .order("invoices.issuing_date" => :desc, "invoices.created_at" => :desc).first
 
       return result unless invoice_subscription
-      result.progressive_billing_invoice = invoice_subscription.invoice
+      invoice = invoice_subscription.invoice
+      result.progressive_billing_invoice = invoice
       result.progressive_billed_amount = result.progressive_billing_invoice.fees_amount_cents
+      result.to_credit_amount = invoice.fees_amount_cents
+
+      if invoice.progressive_billing_credits.exists? || invoice.credit_notes.available.exists?
+        result.to_credit_amount -= invoice.progressive_billing_credits.sum(:amount_cents)
+        result.to_credit_amount -= invoice.credit_notes.available.sum(:credit_amount_cents)
+
+        # if for some reason this goes below zero, it should be zero.
+        result.to_credit_amount = 0 if result.credit_amount.negative?
+      end
 
       result
     end