Make calculate_amount a private method

app/controllers/pfmps_controller.rb

@@ -20,9 +20,9 @@ def new
   def edit; end
 
   def create
-    @pfmp = Pfmp.new(pfmp_params.merge(schooling: @schooling))
+    @pfmp = Pfmp.new
 
-    if PfmpManager.new(@pfmp).update(pfmp_params)
+    if PfmpManager.new(@pfmp).update(pfmp_params.merge(schooling: @schooling))
       redirect_to student_path(@schooling.student),
                   notice: t("pfmps.new.success")
     else

app/services/pfmp_manager.rb

@@ -22,10 +22,12 @@ def update(params)
   end
 
   def update!(params)
+    params = params.to_h.with_indifferent_access
+
     Pfmp.transaction do
       pfmp.update!(params)
-      transition!
       recalculate_amounts! if params[:day_count].present?
+      transition!
     end
   end
 
@@ -47,23 +49,14 @@ def retry_incomplete_payment_request!
 
   def rectify_and_update_attributes!(confirmed_pfmp_params, confirmed_address_params)
     Pfmp.transaction do
-      PfmpManager.new(pfmp).update!(confirmed_pfmp_params)
+      update!(confirmed_pfmp_params)
       pfmp.student.update!(confirmed_address_params)
       pfmp.rectify!
     end
   end
 
-  def calculate_amount
-    return 0 if pfmp.day_count.nil?
-
-    [
-      pfmp.day_count * pfmp.wage.daily_rate,
-      pfmp.wage.yearly_cap - previously_locked_amount
-    ].min
-  end
-
-  def previously_locked_amount
-    other_priced_pfmps
+  def previously_locked_amount(pfmp)
+    other_priced_pfmps(pfmp)
       .map(&:amount)
       .compact
       .sum
@@ -78,31 +71,40 @@ def retry_payment_request!(reasons)
 
   private
 
+  def calculate_amount(target_pfmp)
+    return 0 if target_pfmp.day_count.nil?
+
+    [
+      target_pfmp.day_count * target_pfmp.wage.daily_rate,
+      target_pfmp.wage.yearly_cap - previously_locked_amount(target_pfmp)
+    ].min
+  end
+
   def recalculate_amounts!
     raise PfmpNotModifiableError unless pfmp.can_be_modified?
 
     pfmp.all_pfmps_for_mef.lock!
-    pfmp.update!(amount: calculate_amount)
+    pfmp.update!(amount: calculate_amount(pfmp))
     rebalance_other_pfmps!
   end
 
-  def other_pfmps_for_mef
-    pfmp.all_pfmps_for_mef.excluding(pfmp)
+  def other_pfmps_for_mef(excluded_pfmp)
+    pfmp.all_pfmps_for_mef.excluding(excluded_pfmp)
   end
 
-  def other_priced_pfmps
-    other_pfmps_for_mef
+  def other_priced_pfmps(pfmp)
+    other_pfmps_for_mef(pfmp)
       .where.not(amount: nil)
   end
 
   def rebalancable_pfmps
-    @rebalancable_pfmps ||= other_pfmps_for_mef
+    @rebalancable_pfmps ||= other_pfmps_for_mef(pfmp)
                             .select(&:can_be_rebalanced?)
   end
 
   def rebalance_other_pfmps!
     rebalancable_pfmps.each do |rebalancable_pfmp|
-      rebalancable_pfmp.update!(amount: PfmpManager.new(rebalancable_pfmp).calculate_amount)
+      rebalancable_pfmp.update!(amount: calculate_amount(rebalancable_pfmp))
     end
   end
 

spec/services/pfmp_manager_spec.rb

@@ -113,7 +113,7 @@
   end
 
   describe "#calculate_amount" do # rubocop:disable RSpec/MultipleMemoizedHelpers
-    subject(:amount) { described_class.new(pfmp.reload).calculate_amount }
+    subject(:amount) { described_class.new(pfmp.reload).send(:calculate_amount, pfmp) }
 
     let(:establishment) { create(:establishment) }
     let(:pfmp) do
@@ -202,7 +202,7 @@
     end
 
     def other_pfmps_for_mef
-      manager.send(:other_pfmps_for_mef)
+      manager.send(:other_pfmps_for_mef, pfmp)
     end
 
     context "when there is no other pfmp for that school year and mef" do