From 7a49aafac3a701a9a7408c09275606c3072106ca Mon Sep 17 00:00:00 2001
From: Stephen Paul Weber <singpolyma@singpolyma.net>
Date: Mon, 25 Apr 2022 10:23:44 -0500
Subject: [PATCH] ExpiringLock instead of require expired

We *want* to try billing a little before expiry, to prevent the account lapsing.
So use an ExpiringLock to prevent double-billing races.
---
 lib/bill_plan_command.rb | 45 ++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/lib/bill_plan_command.rb b/lib/bill_plan_command.rb
index e46bb50..25a06e1 100644
--- a/lib/bill_plan_command.rb
+++ b/lib/bill_plan_command.rb
@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 
+require_relative "expiring_lock"
+
 class BillPlanCommand
 	def self.for(customer)
 		return ForUnregistered.new(customer) unless customer.registered?
-		return ForNotExpired.new(customer) unless customer.expires_at <= Time.now
 
 		unless customer.balance > customer.monthly_price
 			return ForLowBalance.new(customer)
@@ -16,19 +17,30 @@ class BillPlanCommand
 		@customer = customer
 	end
 
+	def reload_customer(db)
+		@customer = Command.execution.customer_repo.with(db: db)
+			.find(customer_id).sync
+	end
+
 	def call
-		billed = @customer.bill_plan(note: "Renew account plan") { |db|
-			@customer = Command.execution.customer_repo.with(db: db)
-				.find(@customer.customer_id).sync
-			@customer.balance > @customer.monthly_price &&
-				@customer.expires_at <= Time.now
-		}
-		Command.reply do |reply|
-			reply.note_type = billed ? :info : :error
-			reply.note_text = "#{@customer.customer_id}#{billed ? '' : ' not'} billed"
+		ExpiringLock.new("jmp_customer_bill_plan-#{customer_id}").with {
+			@customer.bill_plan(note: "Renew account plan") { |db|
+				reload_customer(db).balance > @customer.monthly_price
+			}
+		}.then do |billed|
+			Command.reply do |reply|
+				reply.note_type = billed ? :info : :error
+				reply.note_text = "#{customer_id}#{billed ? '' : ' not'} billed"
+			end
 		end
 	end
 
+protected
+
+	def customer_id
+		@customer.customer_id
+	end
+
 	class ForLowBalance
 		def initialize(customer)
 			@customer = customer
@@ -76,17 +88,4 @@ class BillPlanCommand
 			end
 		end
 	end
-
-	class ForNotExpired
-		def initialize(customer)
-			@customer = customer
-		end
-
-		def call
-			Command.reply do |reply|
-				reply.note_type = :error
-				reply.note_text = "#{@customer.customer_id} is not expired"
-			end
-		end
-	end
 end
-- 
2.38.5