Stripe Checkout PaymentsController

payments_controller.rb

class PaymentsController < ApplicationController
  CHECKOUT_SESSION_ID_KEY = :checkout_session_id

  before_action :authenticate_user!

  def new
    stripe_customer = find_or_create_stripe_customer
    checkout_session = create_checkout_session(stripe_customer)

    redirect_to checkout_session.url, allow_other_host: true
  end

  def show
    checkout_session = find_checkout_session(params.fetch(CHECKOUT_SESSION_ID_KEY))
    stripe_customer = Stripe::Customer.retrieve(checkout_session.customer)
    stripe_subscription = Stripe::Subscription.retrieve(checkout_session.subscription)

    StripeSubscription.create!(
      stripe_customer: StripeCustomer.find_by(stripe_customer_id: stripe_customer.id),
      stripe_subscription_id: stripe_subscription.id
    )

    redirect_to new_space_path
  end

  private

  def find_or_create_stripe_customer
    find_stripe_customer || create_stripe_customer
  end

  def find_stripe_customer
    return nil if current_user.stripe_customer_id.blank?

    Stripe::Customer.retrieve(current_user.stripe_customer_id)
  end

  def create_stripe_customer
    stripe_customer = Stripe::Customer.create(
      email: current_user.email,
      metadata: { user_id: current_user.id }
    )

    current_user.create_stripe_customer!(stripe_customer_id: stripe_customer.id)
    stripe_customer
  end

  def create_checkout_session(stripe_customer)
    success_url = url_for(action: :show)
    cancel_url = pricing_index_url

    attributes = {
      mode: "subscription",
      customer: stripe_customer.id,
      line_items: [{ price: ENV["STRIPE_PRICE"], quantity: 1 }],
      success_url: concat_unescaped_stripe_checkout_session_id(success_url),
      cancel_url: concat_unescaped_stripe_checkout_session_id(cancel_url)
    }

    Stripe::Checkout::Session.create(**attributes)
  end

  def concat_unescaped_stripe_checkout_session_id(url)
    stripe_callback_parameter = "#{CHECKOUT_SESSION_ID_KEY}={CHECKOUT_SESSION_ID}"

    if URI(url).query
      url.concat("&#{stripe_callback_parameter}")
    else
      url.concat("?#{stripe_callback_parameter}")
    end
  end

  def find_checkout_session(checkout_session_id)
    Stripe::Checkout::Session.retrieve(checkout_session_id)
  end
end