Stripe Coupon code with one-time use - ruby-on-rails

Question

I have followed the stripe instructions to add coupons to my app. The coupons work great but I want to make a coupon that works all the time but can only be used once per user.
My coupon model
Coupon.rb
class Coupon
include Mongoid::Document
has_many :charges
has_one :manager
validates_presence_of :code, :discount_percent, :coupon_count, :description
validates_uniqueness_of :code
field :code, type: String
field :discount_percent, type: Integer
field :expires_at, type: Date
field :coupon_count, type: Integer
field :description, type: String
def self.get(code)
where(
:code => (normalize_code(code)),
:$and => [
{
:$or => [
{ :coupon_count.gte => 1 },
{ :coupon_count => nil }
]
}, {
:$or => [
{ :expires_at.gte => Date.today },
{ :expires_at => nil }
]
}
]
).first
end
def apply_discount(amount)
discount = amount * (self.discount_percent * 0.01)
(amount - discount.to_i)
end
def discount_percent_human
if discount_percent.present?
discount_percent.to_s + '%'
end
end
def generate_subscription_code(manager)
# Random, unguessable number as a base20 string
# .reverse ensures we don't use first character (which may not take all values)
raw_string = SecureRandom.random_number( 2**80 ).to_s( 20 ).reverse
# Convert Ruby base 20 to better characters for user experience
long_code = raw_string.tr( '0123456789abcdefghij', '234679QWERTYUPADFGHX' )
# Format the code for printing
short_code = long_code[0..3] + '-' + long_code[4..7] + '-' + long_code[8..11]
self.code = short_code
self.discount_percent = 100
self.expires_at = DateTime.now + 1.year
self.coupon_count = 120
self.description = "#{manager.email} Annual Subscription"
save
end
private
def self.normalize_code(code)
code.gsub(/ +/, '').upcase
end
end
Here is my charges controller also
charges_controller.rb
class Managers::ChargesController < ApplicationController
before_filter :authenticate_manager!
def new
#reportapproval = Reportapproval.find(params[:id])
#manager = current_manager
#amount = #reportapproval.manager_request_report_type
end
def create
# Amount in cents
#reportapproval = Reportapproval.find params[:reportapproval_id]
#manager = current_manager
#amount = #reportapproval.manager_request_report_type
#final_amount = #amount
#code = params[:couponCode]
if !#code.blank?
#coupon = Coupon.get(#code)
if #coupon.nil?
flash[:error] = 'Coupon code is not valid or expired.'
redirect_to new_managers_charge_path(id: #reportapproval.id)
return
elsif #coupon.discount_percent == 100
#reportapproval.report_paid = true
#reportapproval.free_coupon_used = true
#reportapproval.save!
#coupon.coupon_count = #coupon.coupon_count - 1
#coupon.save!
redirect_to managers_dashboard_path, :notice => "You have successfully requested a pre-paid report from #{#reportapproval.tenant_last_name} with a 'No-Pay' coupon."
return
else
#final_amount = #coupon.apply_discount(#amount.to_i)
#discount_amount = (#amount.to_i - #final_amount.to_i)
end
if #coupon.present?
charge_metadata = {
:coupon_code => #coupon.code,
:coupon_discount => #coupon.discount_percent_human
}
end
end
charge_metadata ||= {}
customer = Stripe::Customer.create(
:email => #manager.email,
:card => params[:stripeToken]
)
stripe_charge = Stripe::Charge.create(
:customer => customer.id,
:amount => #final_amount,
:description => 'Manager Paid Report',
:currency => 'usd',
:metadata => charge_metadata
)
#charge = Charge.create!(amount: #final_amount, coupon: #coupon, stripe_id: stripe_charge.id)
#reportapproval.report_paid = true
#reportapproval.save!
if #coupon.present?
#coupon.coupon_count = #coupon.coupon_count - 1
#coupon.save!
else
redirect_to managers_dashboard_path, :notice => "You have successfully requested a pre-paid report from #{#reportapproval.tenant_last_name}."
return
end
rescue Stripe::CardError => e
flash[:error] = e.message
redirect_to managers_charges_path
end
end
How can I add the ability to check if the manager has used the coupon before and only allow them to use once?