membership-be/payment_service.py

"""
Payment service for Stripe integration.
Handles subscription creation, checkout sessions, and webhook processing.
"""

import stripe
import os
from dotenv import load_dotenv
from datetime import datetime, timezone, timedelta

# Load environment variables
load_dotenv()

# Initialize Stripe with secret key
stripe.api_key = os.getenv("STRIPE_SECRET_KEY")

# Stripe webhook secret for signature verification
STRIPE_WEBHOOK_SECRET = os.getenv("STRIPE_WEBHOOK_SECRET")

def create_checkout_session(
    user_id: str,
    user_email: str,
    plan_id: str,
    stripe_price_id: str,
    success_url: str,
    cancel_url: str
):
    """
    Create a Stripe Checkout session for subscription payment.

    Args:
        user_id: User's UUID
        user_email: User's email address
        plan_id: SubscriptionPlan UUID
        stripe_price_id: Stripe Price ID for the plan
        success_url: URL to redirect after successful payment
        cancel_url: URL to redirect if user cancels

    Returns:
        dict: Checkout session object with session ID and URL
    """
    try:
        # Create Checkout Session
        checkout_session = stripe.checkout.Session.create(
            customer_email=user_email,
            payment_method_types=["card"],
            line_items=[
                {
                    "price": stripe_price_id,
                    "quantity": 1,
                }
            ],
            mode="subscription",
            success_url=success_url,
            cancel_url=cancel_url,
            metadata={
                "user_id": str(user_id),
                "plan_id": str(plan_id),
            },
            subscription_data={
                "metadata": {
                    "user_id": str(user_id),
                    "plan_id": str(plan_id),
                }
            }
        )

        return {
            "session_id": checkout_session.id,
            "url": checkout_session.url
        }

    except stripe.error.StripeError as e:
        raise Exception(f"Stripe error: {str(e)}")


def verify_webhook_signature(payload: bytes, sig_header: str) -> dict:
    """
    Verify Stripe webhook signature and construct event.

    Args:
        payload: Raw webhook payload bytes
        sig_header: Stripe signature header

    Returns:
        dict: Verified webhook event

    Raises:
        ValueError: If signature verification fails
    """
    try:
        event = stripe.Webhook.construct_event(
            payload, sig_header, STRIPE_WEBHOOK_SECRET
        )
        return event
    except ValueError as e:
        raise ValueError(f"Invalid payload: {str(e)}")
    except stripe.error.SignatureVerificationError as e:
        raise ValueError(f"Invalid signature: {str(e)}")


def get_subscription_end_date(billing_cycle: str = "yearly") -> datetime:
    """
    Calculate subscription end date based on billing cycle.

    Args:
        billing_cycle: "yearly" or "monthly"

    Returns:
        datetime: End date for the subscription
    """
    now = datetime.now(timezone.utc)

    if billing_cycle == "yearly":
        # Add 1 year
        return now + timedelta(days=365)
    elif billing_cycle == "monthly":
        # Add 1 month (approximation)
        return now + timedelta(days=30)
    else:
        # Default to yearly
        return now + timedelta(days=365)


def create_stripe_price(
    product_name: str,
    price_cents: int,
    billing_cycle: str = "yearly"
) -> str:
    """
    Create a Stripe Price object for a subscription plan.

    Args:
        product_name: Name of the product/plan
        price_cents: Price in cents
        billing_cycle: "yearly" or "monthly"

    Returns:
        str: Stripe Price ID
    """
    try:
        # Create a product first
        product = stripe.Product.create(name=product_name)

        # Determine recurring interval
        interval = "year" if billing_cycle == "yearly" else "month"

        # Create price
        price = stripe.Price.create(
            product=product.id,
            unit_amount=price_cents,
            currency="usd",
            recurring={"interval": interval},
        )

        return price.id

    except stripe.error.StripeError as e:
        raise Exception(f"Stripe error creating price: {str(e)}")


def get_customer_portal_url(stripe_customer_id: str, return_url: str) -> str:
    """
    Create a Stripe Customer Portal session for subscription management.

    Args:
        stripe_customer_id: Stripe Customer ID
        return_url: URL to return to after portal session

    Returns:
        str: Customer portal URL
    """
    try:
        session = stripe.billing_portal.Session.create(
            customer=stripe_customer_id,
            return_url=return_url,
        )
        return session.url
    except stripe.error.StripeError as e:
        raise Exception(f"Stripe error creating portal session: {str(e)}")