Payment gateway integration in Ruby on Rails requires careful planning and robust implementation. I’ve worked with various payment providers, and I’ll share proven techniques to build reliable payment processing systems.

Payment Provider Abstraction

Creating an abstraction layer for payment providers allows seamless switching between gateways. This approach isolates gateway-specific code and provides a unified interface for your application.

module PaymentGateway
  class Base
    def charge(amount:, currency:, source:)
      raise NotImplementedError
    end
    
    def refund(transaction_id:, amount:)
      raise NotImplementedError
    end
  end
  
  class Stripe < Base
    def charge(amount:, currency:, source:)
      Stripe::Charge.create(
        amount: amount,
        currency: currency,
        source: source
      )
    end
  end
  
  class PayPal < Base
    def charge(amount:, currency:, source:)
      PayPal::Payment.new.create(
        amount: amount,
        currency: currency,
        source_token: source
      )
    end
  end
end

Transaction handling requires atomic operations and proper error management. I recommend using ActiveRecord transactions and implementing retry mechanisms for failed payments.

class TransactionManager
  include Retriable
  
  def process(order)
    ActiveRecord::Base.transaction do
      payment = create_payment(order)
      
      retriable(tries: 3, on: NetworkError) do
        response = gateway.charge(build_charge_params(order))
        update_payment_status(payment, response)
      end
      
      notify_customer(payment)
    end
  end
end

Webhook handling is crucial for asynchronous payment updates. Implement signature verification and idempotency checks:

class WebhookProcessor
  def process(payload, signature)
    return unless valid_signature?(payload, signature)
    
    event = parse_webhook(payload)
    
    WebhookEvent.transaction do
      return if WebhookEvent.exists?(external_id: event.id)
      
      WebhookEvent.create!(
        external_id: event.id,
        event_type: event.type,
        payload: payload
      )
      
      process_event(event)
    end
  end
end

Refund processing requires careful state management and proper error handling:

class RefundService
  def process(payment, amount)
    return false unless payment.refundable?
    
    Refund.transaction do
      refund = Refund.create!(
        payment: payment,
        amount: amount,
        status: :pending
      )
      
      response = gateway.refund(
        transaction_id: payment.transaction_id,
        amount: amount
      )
      
      update_refund_status(refund, response)
    end
  rescue GatewayError => e
    handle_refund_error(payment, e)
    false
  end
end

Error recovery requires comprehensive logging and automated recovery processes:

class ErrorRecovery
  def recover_failed_payments
    Payment.failed.find_each do |payment|
      next if payment.attempts >= 3
      
      begin
        retry_payment(payment)
      rescue StandardError => e
        Rails.logger.error("Recovery failed for payment #{payment.id}: #{e.message}")
        notify_admin(payment, e)
      end
    end
  end
end

Payment retry logic implementation with exponential backoff:

class RetryManager
  def calculate_next_retry(payment)
    return nil if payment.attempts >= 3
    
    base_delay = 30.minutes
    exponential_delay = base_delay * (2 ** payment.attempts)
    Time.current + exponential_delay
  end
end

Security compliance requires proper data encryption and PCI DSS guidelines adherence:

class SecurePaymentData
  def encrypt_card_data(card_number)
    cipher = OpenSSL::Cipher.new('aes-256-gcm')
    cipher.encrypt
    cipher.key = encryption_key
    
    encrypted_data = cipher.update(card_number) + cipher.final
    { data: encrypted_data, iv: cipher.iv, auth_tag: cipher.auth_tag }
  end
end

For multi-provider support, implement a factory pattern:

class PaymentGatewayFactory
  def self.create(provider_name)
    case provider_name.to_sym
    when :stripe
      PaymentGateway::Stripe.new
    when :paypal
      PaymentGateway::PayPal.new
    else
      raise UnsupportedGatewayError
    end
  end
end

Implement comprehensive logging for transaction tracking:

class TransactionLogger
  def log_transaction(payment)
    Rails.logger.info(
      payment_id: payment.id,
      amount: payment.amount,
      status: payment.status,
      provider: payment.provider,
      timestamp: Time.current
    )
  end
end

Add payment validation rules:

class PaymentValidator
  def validate(payment)
    errors = []
    errors << "Invalid amount" unless valid_amount?(payment.amount)
    errors << "Invalid currency" unless valid_currency?(payment.currency)
    errors << "Invalid card" unless valid_card?(payment.source)
    errors.empty? ? true : errors
  end
end

Create a notification system for payment status updates:

class PaymentNotifier
  def notify(payment)
    return unless payment.status_changed?
    
    notification = {
      to: payment.customer.email,
      template: status_template(payment),
      variables: {
        amount: payment.amount,
        status: payment.status,
        transaction_id: payment.transaction_id
      }
    }
    
    NotificationService.deliver(notification)
  end
end

This implementation provides a solid foundation for payment processing in Rails applications. Regular testing, monitoring, and maintenance ensure reliable payment operations. Consider implementing additional features like payment analytics, fraud detection, and automated reconciliation based on your specific needs.

Remember to handle edge cases, implement proper logging, and maintain comprehensive documentation. Regular security audits and compliance checks are essential for maintaining a secure payment system.

The success of a payment integration system largely depends on proper error handling, reliable retry mechanisms, and clear logging. Keep the code modular and maintainable while following security best practices.