Stripe Cancellations In Fastapi And Sqlmodel

Today I am working on fokais.com, trying to get to a point where I can launch by workig through stripe integrations. This is my first time using stripe, so there has been quite a bit to learn, and I am probably building in more than I need to before launching, but I am learning, and not in a rush to launch.

I am building the fokais backent in python primarilyt with fastapi and sqlmodel on sqlite. My billing integration is going to be all Stripe.

Stripe Subscription Cancellations Docs

Here is a link to the stripe docs for your refrence, especially if you want to see how to cancel subscriptions in other languages. They include code samples for many popular languages.

User Model

This is the part of the user model that includes the cancel and reactivate methods. It pretty much follows the stripe guide.

        
class UserBase(SQLModel, table=False):  # type: ignore[call-arg]
    username: str = Field(unique=True)
    full_name: str
    email: str
    email_verified: bool = False
    disabled: bool = False
    signup_date: Optional[datetime] = Field(default_factory=datetime.utcnow)
    stripe_customer_id: Optional[str]

    def cancel_subscription(self):
        for subscription in self.active_subscriptions:
            stripe.Subscription.modify(
                subscription.id,
                cancel_at_period_end=True,
            )
        self.refresh()

    def reactivate_subscription(self):
        for subscription in self.active_subscriptions:
            stripe.Subscription.modify(
                subscription.id,
                cancel_at_period_end=False,
            )
        self.refresh()

Cancellations api

Here is the cancellations api. I created an are you sure form that I can link to from the accounts page with a normal anchor tag. Note that I am doing a POST request to do the cancellation from a form. I want this to work for any user whether there is js or not. This is an operation that will change the users data, and I want to make sure that it avoids all browser and cdn caching. As a scrappy startup we are running light on infrastructure and are caching hard at the CDN to avoid excessive server hits.

        
@pricing_router.get("/cancel")
@pricing_router.get("/cancel/")
def get_cancel(
    request: Request,
    current_user: Annotated[User, Depends(get_current_user_if_logged_in)],
):
    return config.templates.TemplateResponse(
        "cancel.html",
        {
            "request": request,
            "prices": products.prices,
            "products": products.products,
            "current_user": current_user,
        },
    )


@pricing_router.post("/cancel")
@pricing_router.post("/cancel/")
def post_cancel(
    request: Request,
    current_user: Annotated[User, Depends(get_current_user_if_logged_in)],
):
    current_user.cancel_subscription()
    return HTMLResponse('<p id="cancel" hx-swap-oob="outerHTML">Your Subscription has been Cancelled</p>')

Reactivations

Reactivating accounts looks just about the same as cancelling, only flippng True to False.

        
@pricing_router.get("/reactivate")
@pricing_router.get("/reactivate/")
def get_reactivate(
    request: Request,
    current_user: Annotated[User, Depends(get_current_user_if_logged_in)],
):
    return config.templates.TemplateResponse(
        "reactivate.html",
        {
            "request": request,
            "prices": products.prices,
            "products": products.products,
            "current_user": current_user,
        },
    )


@pricing_router.post("/reactivate")
@pricing_router.post("/reactivate/")
def post_reactivate(
    request: Request,
    current_user: Annotated[User, Depends(get_current_user_if_logged_in)],
):
    current_user.reactivate_subscription()
    return HTMLResponse('<p id="reactivate" hx-swap-oob="outerHTML">Your Subscription has been reactivated</p>')

Full User Model

This is the full user model, completely subject to change in the future, but it includes the cancel and reactivate methods.

        
class UserBase(SQLModel, table=False):  # type: ignore[call-arg]
    username: str = Field(unique=True)
    full_name: str
    email: str
    email_verified: bool = False
    disabled: bool = False
    signup_date: Optional[datetime] = Field(default_factory=datetime.utcnow)
    stripe_customer_id: Optional[str]

    @property
    def session(self):
        return next(get_session())

    @classmethod
    def get_by_id(cls, id):
        return next(get_session()).get(cls, id)

    def refresh(self):
        cache.set(f"active_subscriptions_{self.id}", None, 3600)
        cache.set(f"active_products_{self.id}", None, 3600)

    def get_checkout_sessions(self):
        return [
            stripe.checkout.Session.retrieve(s.stripe_checkout_session_id)
            for s in self.session.exec(select(CheckoutSession).where(CheckoutSession.user_id == self.id)).all()
            if s.stripe_checkout_session_id is not None
        ]

    def get_active_subscriptions(self):
        subscriptions = [
            s.subscription
            for s in [
                stripe.checkout.Session.retrieve(s.stripe_checkout_session_id)
                for s in self.session.exec(select(CheckoutSession).where(CheckoutSession.user_id == self.id)).all()
                if s.stripe_checkout_session_id is not None
            ]
            if s.status == "complete"
        ]
        active_subscriptions = [stripe.Subscription.retrieve(subscription) for subscription in subscriptions]
        return active_subscriptions

    def has_active_subscription(self):
        return len(self.active_subscriptions) > 0

    @property
    def active_subscriptions(self):
        active_subscriptions = cache.get(f"active_subscriptions_{self.id}")
        if active_subscriptions is not None:
            return active_subscriptions
        active_subscriptions = self.get_active_subscriptions()
        cache.set(f"active_subscriptions_{self.id}", active_subscriptions, 3600)

        return active_subscriptions

    @property
    def active_plans(self):
        subscriptions = self.active_subscriptions
        plans = [subscription.plan for subscription in subscriptions]
        return plans

    @property
    def subscription_to_plan(self):
        subscriptions = self.active_subscriptions
        plans = {subscription.id: subscription.plan.id for subscription in subscriptions}
        return plans

    @property
    def plan_to_subscription(self):
        plans = {v: k for k, v in self.subscription_to_plan.items()}

        return plans

    def get_active_products(self):
        plans = self.active_plans
        products = [stripe.Product.retrieve(plan.product) for plan in plans]
        return products

    @property
    def plan_to_product(self):
        plans = self.active_plans
        products = {plan.id: stripe.Product.retrieve(plan.product).id for plan in plans}
        return products

    @property
    def prodct_to_plan(self):
        plans = self.active_plans
        products = {stripe.Product.retrieve(plan.product).id: plan.id for plan in plans}
        return products

    @property
    def active_products(self):
        products = cache.get(f"active_products_{self.id}")
        if products is not None:
            return products
        products = self.get_active_products()
        cache.set(f"active_products_{self.id}", products, 3600)

        return products

    @property
    def best_active_subscription(self):
        subscriptions = self.active_subscriptions
        return subscriptions[0]

    @property
    def best_active_product(self):
        products = self.active_products
        products.sort(key=lambda p: p.metadata.get('level', 0))
        return products[0]

    @property
    def best_active_subscription(self):
        subscription_id = self.plan_to_subscription[self.prodct_to_plan[self.best_active_product.id]]
        return stripe.Subscription.retrieve(subscription_id)

    @property
    def config(self):
        product = self.best_active_product
        return product.metadata

    def subscription_status(self):
        subscriptions = self.active_subscriptions()

    def cancel_subscription(self):
        for subscription in self.active_subscriptions:
            stripe.Subscription.modify(
                subscription.id,
                cancel_at_period_end=True,
            )
        self.refresh()

    def reactivate_subscription(self):
        for subscription in self.active_subscriptions:
            stripe.Subscription.modify(
                subscription.id,
                cancel_at_period_end=False,
            )
        self.refresh()