Implémentation Paymill (code du slide #27 de mon talk à Lyon.rb le 10/04/2013 : http://michaelbaudino.github.io/presentation-paiements).

browser.js.coffee

# Initialize Paymill public API key
window.PAYMILL_PUBLIC_KEY = '8a8394c13bb2c160013bb7f6af8a1c85'

# Retrieve Paymill javascript snippet (the "bridge")
$.getScript('https://bridge.paymill.com')

# This should be called when the user validates the HTML form
paymill.createToken
  number: $('#card-number').val()           # required, without spaces and hyphens
  exp_month: $('#card-expiry-month').val()  # required
  exp_year: $('#card-expiry-year').val()    # required, four digits e.g. "2016"
  cvc: $('#card-cvc').val()                 # required
  amount_int: 4200                          # required, integer e.g. "15" for 0.15 EUR
  currency: 'EUR'                           # required, ISO 4217 e.g. "EUR" or "GBP"
, (error, result) ->
  if error
    alert 'error.apierror'
  else
    $.ajax(
      type: 'POST'
      url: '/pay/'
      dataType: 'json'
      data:
        token: result.token
      success: (data) ->
        alert 'Paiement réussi'
      error: (data) ->
        alert 'Paiement échoué'
    )

controller.rb

# This gist is using the paymill gem : https://github.com/dkd/paymill-ruby

# This is the real controller
def process_payment
  respond_to do |format|
    format.html { not_implemented__use(:json) }
    format.json begin
      response = Paymill::Transaction.create(
        amount:         4200,
        currency:       'EUR',
        token:          params[:token]
      )
      if response.status == 'closed' or response.status == :closed
        render :json => response, :status => :ok
      else
        raise Exception.new('Payment refused')
      end
    rescue Exception => e
      render :json => {:error => e.to_s}, :status => :unauthorized
    end
  end
end

form.html

<label for="card-number">Numéro de carte</label>
<input id="card-number" type="text" maxlength="16" />

<label for="card-expiry-month">Mois d'expiration</label>
<input id="card-expiry-month" type="text" placeholder="MM" maxlength="2" />

<label for="card-expiry-year">Année d'expiration</label>
<input id="card-expiry-year" type="text" placeholder="AAAA" maxlength="4" />

<label for="card-cvc">Numéro de sécurité</label>
<input id="card-cvc" type="text" maxlength="3" />

initializer.rb

# Configure Paymill by retrieving your private API key in an environment variable
Paymill::api_key = ENV['PAYMILL_API_KEY']