Here’s the mermaid diagram code for a web application with Stripe integration, including three different subscription plans:

mermaid
graph TB

subgraph Web Application
    UI["User Interface"]
    BE["Backend Server"]
    API["REST API"]
    DB["Database"]
end

subgraph Stripe
    SCP["Stripe Checkout Page"]
    SWH["Stripe Webhook"]
    SC["Stripe Customers"]
    SS["Stripe Subscriptions"]
    SPI["Stripe Payments API"]
end

UI -->|1. Select Plan| BE
BE -->|2. Create Checkout Session| SPI
SPI -->|3. Session ID| BE
BE -->|4. Redirect to Checkout| UI
UI -->|5. Checkout| SCP
SCP -->|6. Payment Success| SWH
SWH -->|7. Handle Event| BE
BE -->|8. Update User Subscription| DB
BE -->|9. Communicate with Stripe API| SPI
SPI -->|a. Manage Subscriptions| SS
SPI -->|b. Manage Customers| SC

classDef stripe fill:
          
          #f6e05e
       ,stroke:#333,stroke-width:2px;
class SCP,SWH,SC,SS,SPI stripe

This code snippet describes the following flow for a web application integrating with Stripe for subscription management:

1. The user interacts with the User Interface to select one of the three subscription plans.
2. The Backend Server creates a Checkout Session with Stripe’s Payments API.
3. The Stripe Payments API returns a Session ID to the Backend Server.
4. The Backend Server redirects the user to the Stripe Checkout Page with the Session ID.
5. The user completes the checkout process on the Stripe Checkout Page.
6. Upon successful payment, Stripe triggers an event to the Stripe Webhook.
7. The Stripe Webhook sends the event to the Backend Server, which handles it appropriately.
8. The Backend Server updates the user’s subscription status in the Database.
9. Additionally, the Backend Server communicates with the Stripe API as needed to manage subscriptions and customers.

The classes at the end of the code snippet are used to apply specific styling to the Stripe-related components, highlighting them in the diagram.