Ruby script to find duplicate Stripe customers

duplicate_stripe_customers.rb

require 'stripe'

Stripe.api_key = "YOUR_STRIPE_API_KEY"
duplicate_customers = []
last_customer_id = nil # Cursor for paginating through results

# Stripe can retrieve a maximum of 100 customers in one go, so we need to loop.
loop do
  customers = Stripe::Customer.all(limit: 100, starting_after: last_customer_id)
  emails = customers.data.each.map { |d| d["email"] }
  emails.detect { |email| duplicate_customers << email if emails.count(email) > 1 }

  break if customers.count != 100
  last_customer_id = customers.data[99]["id"]
end

if duplicate_customers.empty?
  puts "No duplicate customers found!"
else
  puts "Duplicate Customers:\n"
  puts "--------------------\n"
  duplicate_customers.each { |dup| puts dup }
end