割引を動的に更新する

# Set your secret key. Remember to switch to your live secret key in production.
# See your keys here: https://dashboard.stripe.com/apikeys
Stripe.api_key = 
'sk_test_BQokikJOvBiI2HlWgH4olfQ2'
Stripe.api_version = '2025-03-31.basil; checkout_server_update_beta=v1;'

curl https://api.stripe.com/v1/checkout/sessions \
  -u "
sk_test_BQokikJOvBiI2HlWgH4olfQ2
:" \
  -H "Stripe-Version: 2025-03-31.basil; checkout_server_update_beta=v1;" \
  -d ui_mode=custom \
  -d "permissions[update_discounts]"=server_only \
  -d "line_items[0][price]"=
"{{PRICE_ID}}" \
  -d "line_items[0][quantity]"=1 \
  -d mode=payment \
  --data-urlencode return_url="https://example.com/return"

require 'sinatra'
require 'json'
require 'stripe'

set :port, 4242

# Set your secret key. Remember to switch to your live secret key in production!
# See your keys here: https://dashboard.stripe.com/apikeys
Stripe.api_key = 
"sk_test_BQokikJOvBiI2HlWgH4olfQ2"

# Return a boolean indicating whether the discounts are valid.
def validate_discounts(discounts, session
  # Basic validation - ensure we only have one discount if any
  return true if discounts.empty? || discounts == ""

  # Ensure only one discount is being applied
  return false if discounts.is_a?(Array) && discounts.length > 1

  # Add your own validation logic here
  # For example, validate promo codes against your internal system
  true
end

# Return an array of the updated discounts or the original ones if no update is needed.
def recompute_discounts(discounts, session)
  # If removing discounts, return empty
  return [] if discounts.empty? || discounts == ""

  # Example: Access your internal discounts system
  # This could be based on customer ID, promo codes, cart value, etc.
  customer_id = session.customer || session.client_reference_id
  cart_total = session.amount_total

  # Example internal discount calculation
  discount_amount = calculate_customer_discount(customer_id, cart_total)

  if discount_amount > 0
    # Create a dynamic discount using coupon_data
    [{
      coupon_data: {
        name: "Customer Discount",
        amount_off: discount_amount,
        currency: session.currency || 'usd'
      }
    }]
  else
    # No discount applicable
    []
  end
end

# Example function to integrate with your internal discounts system
def calculate_customer_discount(customer_id, cart_total)
  # Example logic - replace with your actual discount system
  # This could check:
  # - Customer loyalty tier
  # - Active promotions
  # - Cart value thresholds
  # - Seasonal discounts

  # Example: 10% off for carts over 100 USD, max 20 USD discount
  if cart_total > 10000  # 100 USD in cents
    discount = [cart_total * 0.1, 2000].min  # Max 20 USD discount
    discount.to_i
  else
    0
  end
end

post '/update-discounts' do
  content_type :json
  request.body.rewind
  request_data = JSON.parse(request.body.read)

  checkout_session_id = request_data['checkout_session_id']
  discounts = request_data['discounts']

  # 1. Retrieve the Checkout Session
  session = Stripe::Checkout::Session.retrieve(checkout_session_id)

  # 2. Validate the discounts
  if !validate_discounts(discounts, session)
    return { type: 'error', message: 'Your discounts are invalid. Please refresh your session.' }.to_json
  end

  # 3. Recompute the discounts with your custom logic
  discounts = recompute_discounts(discounts, session)

  # 4. Update the Checkout Session with the new discounts
  if discounts
    Stripe::Checkout::Session.update(checkout_session_id, {
      discounts: discounts,
    })

    return { type: 'object', value: { succeeded: true } }.to_json
  else
    return { type: 'error', message: "We could not update your discounts. Please try again." }.to_json
  end
end