manager-service/ManagerService/Services/StripeService.cs

using System.Threading.Tasks;
using ManagerService.Data;
using ManagerService.Helpers;
using Microsoft.Extensions.Options;
using Stripe;
using Stripe.Checkout;

namespace ManagerService.Services
{
    /// <summary>
    /// Stripe integration for the Essentiel plan self-service subscription (customer creation,
    /// Checkout Session, Billing Portal Session, webhook signature verification). Both Checkout
    /// and the Billing Portal are hosted by Stripe — no card form is built in any of our own apps.
    /// </summary>
    public class StripeService
    {
        private readonly StripeSettings _settings;
        private readonly CustomerService _customerService;
        private readonly SessionService _checkoutSessionService;
        private readonly Stripe.BillingPortal.SessionService _billingPortalSessionService;

        public StripeService(IOptions<StripeSettings> settings)
        {
            _settings = settings.Value;
            StripeConfiguration.ApiKey = _settings.SecretKey;
            _customerService = new CustomerService();
            _checkoutSessionService = new SessionService();
            _billingPortalSessionService = new Stripe.BillingPortal.SessionService();
        }

        public async Task<string> CreateCustomerAsync(Instance instance)
        {
            var customer = await _customerService.CreateAsync(new CustomerCreateOptions
            {
                Name = instance.Name,
                Metadata = new System.Collections.Generic.Dictionary<string, string>
                {
                    { "instanceId", instance.Id },
                },
            });
            return customer.Id;
        }

        /// <summary>
        /// Create a Stripe Checkout Session for the Essentiel plan subscription.
        /// Stripe Tax is applied automatically based on the customer's billing details.
        /// </summary>
        public async Task<string> CreateCheckoutSessionAsync(Instance instance, string successUrl, string cancelUrl)
        {
            var options = new SessionCreateOptions
            {
                Mode = "subscription",
                Customer = instance.StripeCustomerId,
                LineItems = new System.Collections.Generic.List<SessionLineItemOptions>
                {
                    new SessionLineItemOptions
                    {
                        Price = _settings.EssentielPriceId,
                        Quantity = 1,
                    },
                },
                AutomaticTax = new SessionAutomaticTaxOptions { Enabled = true },
                SuccessUrl = successUrl,
                CancelUrl = cancelUrl,
                Metadata = new System.Collections.Generic.Dictionary<string, string>
                {
                    { "instanceId", instance.Id },
                },
            };

            var session = await _checkoutSessionService.CreateAsync(options);
            return session.Url;
        }

        /// <summary>
        /// Create a Stripe Billing Portal Session: the customer manages card, invoices and
        /// cancellation on Stripe's own pages. Nothing to build on our side beyond the redirect.
        /// </summary>
        public async Task<string> CreateBillingPortalSessionAsync(Instance instance, string returnUrl)
        {
            var session = await _billingPortalSessionService.CreateAsync(
                new Stripe.BillingPortal.SessionCreateOptions
                {
                    Customer = instance.StripeCustomerId,
                    ReturnUrl = returnUrl,
                });
            return session.Url;
        }

        public Event ConstructWebhookEvent(string json, string stripeSignatureHeader)
        {
            return EventUtility.ConstructEvent(json, stripeSignatureHeader, _settings.WebhookSecret);
        }
    }
}