# Overview

Solidus has a flexible payments system that allows multiple payment methods to be used during checkout.

The logic for processing payments is decoupled from Solidus's orders system. This allows you to easily define your own payment methods with custom processing logic.

The payments system has many moving parts. The following lists summarizes the essential parts of the payments system:

1. Payment service providers. Before your store can have a functional payments system, you need create an account with a payment service provider Braintree or Stripe.
2. Payment methods. A store may have multiple Spree::PaymentMethods configured. Payment methods send payment information to a payment service provider.
3. Payments. After a customer submits their payment details for an order, a new Spree::Payment object is created.
4. Payment sources. Spree::Payments can have a payment source. The source depends on the payment method that is used. For example, the payment source could be a Spree::CreditCard, Spree::StoreCredit, or a non-Spree model provided by your payment service provider integration.
5. Payment processing. Once an order is complete, a payment can be processed. At this point, the Spree::Payment::Processing class calls on Spree::PaymentMethod and attempts to capture the payment.

The complexity of your store's payments system depends on the payment gateways that you use and the amount of payment methods that you need to support.

The rest of this article summarizes these parts of the system.

# Payment service providers (PSPs)

In order for you to successfully process payments, your Spree::PaymentMethods need to send information to a payment service provider (PSP).

The Solidus community has created a number of Solidus extensions to connect you popular PSPs like Braintree, Adyen, Affirm, and Paybright.

Typically, PSP integrations use the Spree::PaymentMethod base class to build out to the PSP's specifications and API.

Solidus is not built to process payments by itself, and it does not include any integrations for popular PSPs. You must install an extension or create your own integration.

# Payment methods

In Solidus, each Spree::PaymentMethod represents a way that your store chooses to accept payments. For example, you may want to set up separate payment methods for PayPal payments and credit card payments.

Solidus does not include working payment methods by default. Typically, you need to integrate your payment method with a payment service provider.

Solidus includes bogus credit card methods for testing, a basic Spree::PaymentMethod::CreditCard class that you can use for modeling your own credit card payment methods, and some other basic payment methods.

For more information, see the Payment methods article.

# Payments

The Spree::Payment model in Solidus tracks payments. A new payment is created once the customer has submitted their payment details during checkout.

Payments relate to a specific Spree::Order, as well as one of your available Spree::PaymentMethods and a payment source (which could be a Spree::CreditCard, a Spree::StoreCredit or some other non-Spree model).

Note that a payment being created does not mean that a payment has been made successfully. The Spree::Payment model has a state machine that tracks the status of a payment. Once the payment is processed by your payment service provider, the state could become complete, failed, void, and so on.

# Payment sources

Each Spree::Payment tracks a payment source. The payment source depends on the types of payments you accept for each payment method.

For example, if you use Solidus's built-in Spree::PaymentMethod::CreditCart payment method, the payment source class should always be set to Spree::CreditCard.

Your payment methods may have more complex payment source classes. For example, if you use the solidus_paypal_braintree gem, payments made using your Braintree payment methods have the payment source SolidusPaypalBraintree::Source. However, the SolidusPaypalBraintree::Source class has a payment_type method that could have a value of ApplePay, CreditCard or PayPalAccount.

# Payment processing

The Spree::Payment::Processing class's process! method can can operate on completed orders. It attempts to capture orders, invoking the customer's selected Spree::PaymentMethod and sending payment details to the payment service provider.

For more information about processing payments, see the Payment processing article.