wakapi/routes/subscription.go

package routes

import (
	"encoding/json"
	"errors"
	"fmt"
	"github.com/emvi/logbuch"
	"github.com/gorilla/mux"
	conf "github.com/muety/wakapi/config"
	"github.com/muety/wakapi/middlewares"
	"github.com/muety/wakapi/models"
	"github.com/muety/wakapi/services"
	"github.com/stripe/stripe-go/v74"
	stripePortalSession "github.com/stripe/stripe-go/v74/billingportal/session"
	stripeCheckoutSession "github.com/stripe/stripe-go/v74/checkout/session"
	stripeCustomer "github.com/stripe/stripe-go/v74/customer"
	stripePrice "github.com/stripe/stripe-go/v74/price"
	"github.com/stripe/stripe-go/v74/webhook"
	"io/ioutil"
	"net/http"
	"strings"
	"time"
)

/*
  How to integrate with Stripe?
  ---
  1. Create a plan with recurring payment (https://dashboard.stripe.com/test/products?active=true), copy its ID and save it as 'standard_price_id'
  2. Create a webhook (https://dashboard.stripe.com/test/webhooks), with target URL '/subscription/webhook' and events ['customer.subscription.created', 'customer.subscription.updated', 'customer.subscription.deleted', 'checkout.session.completed'], copy the endpoint secret and save it to 'stripe_endpoint_secret'
  3. Create a secret API key (https://dashboard.stripe.com/test/apikeys), copy it and save it to 'stripe_secret_key'
  4. Copy the publishable API key (https://dashboard.stripe.com/test/apikeys) and save it to 'stripe_api_key'
*/

type SubscriptionHandler struct {
	config       *conf.Config
	userSrvc     services.IUserService
	mailSrvc     services.IMailService
	keyValueSrvc services.IKeyValueService
	httpClient   *http.Client
}

func NewSubscriptionHandler(
	userService services.IUserService,
	mailService services.IMailService,
	keyValueService services.IKeyValueService,
) *SubscriptionHandler {
	config := conf.Get()

	if config.Subscriptions.Enabled {
		stripe.Key = config.Subscriptions.StripeSecretKey

		price, err := stripePrice.Get(config.Subscriptions.StandardPriceId, nil)
		if err != nil {
			logbuch.Fatal("failed to fetch stripe plan details: %v", err)
		}
		config.Subscriptions.StandardPrice = strings.TrimSpace(fmt.Sprintf("%2.f €", price.UnitAmountDecimal/100.0)) // TODO: respect actual currency

		logbuch.Info("enabling subscriptions with stripe payment for %s / month", config.Subscriptions.StandardPrice)
	}

	return &SubscriptionHandler{
		config:       config,
		userSrvc:     userService,
		mailSrvc:     mailService,
		keyValueSrvc: keyValueService,
		httpClient:   &http.Client{Timeout: 10 * time.Second},
	}
}

// https://stripe.com/docs/billing/quickstart?lang=go

func (h *SubscriptionHandler) RegisterRoutes(router *mux.Router) {
	if !h.config.Subscriptions.Enabled {
		return
	}

	subRouterPublic := router.PathPrefix("/subscription").Subrouter()
	subRouterPublic.Path("/success").Methods(http.MethodGet).HandlerFunc(h.GetCheckoutSuccess)
	subRouterPublic.Path("/cancel").Methods(http.MethodGet).HandlerFunc(h.GetCheckoutCancel)
	subRouterPublic.Path("/webhook").Methods(http.MethodPost).HandlerFunc(h.PostWebhook)

	subRouterPrivate := subRouterPublic.PathPrefix("").Subrouter()
	subRouterPrivate.Use(
		middlewares.NewAuthenticateMiddleware(h.userSrvc).WithRedirectTarget(defaultErrorRedirectTarget()).Handler,
	)
	subRouterPrivate.Path("/checkout").Methods(http.MethodPost).HandlerFunc(h.PostCheckout)
	subRouterPrivate.Path("/portal").Methods(http.MethodPost).HandlerFunc(h.PostPortal)
}

func (h *SubscriptionHandler) PostCheckout(w http.ResponseWriter, r *http.Request) {
	if h.config.IsDev() {
		loadTemplates()
	}

	user := middlewares.GetPrincipal(r)
	if user.Email == "" {
		http.Redirect(w, r, fmt.Sprintf("%s/settings?error=%s#subscription", h.config.Server.BasePath, "missing e-mail address"), http.StatusFound)
		return
	}

	if err := r.ParseForm(); err != nil {
		http.Redirect(w, r, fmt.Sprintf("%s/settings?error=%s#subscription", h.config.Server.BasePath, "missing form values"), http.StatusFound)
		return
	}

	checkoutParams := &stripe.CheckoutSessionParams{
		Mode: stripe.String(string(stripe.CheckoutSessionModeSubscription)),
		LineItems: []*stripe.CheckoutSessionLineItemParams{
			{
				Price:    &h.config.Subscriptions.StandardPriceId,
				Quantity: stripe.Int64(1),
			},
		},
		ClientReferenceID: &user.ID,
		SuccessURL:        stripe.String(fmt.Sprintf("%s%s/subscription/success", h.config.Server.PublicUrl, h.config.Server.BasePath)),
		CancelURL:         stripe.String(fmt.Sprintf("%s%s/subscription/cancel", h.config.Server.PublicUrl, h.config.Server.BasePath)),
	}

	if user.StripeCustomerId != "" {
		checkoutParams.Customer = &user.StripeCustomerId
	} else {
		checkoutParams.CustomerEmail = &user.Email
	}

	session, err := stripeCheckoutSession.New(checkoutParams)
	if err != nil {
		conf.Log().Request(r).Error("failed to create stripe checkout session: %v", err)
		http.Redirect(w, r, fmt.Sprintf("%s/settings?error=%s#subscription", h.config.Server.BasePath, "something went wrong"), http.StatusFound)
		return
	}

	http.Redirect(w, r, session.URL, http.StatusSeeOther)
}

func (h *SubscriptionHandler) PostPortal(w http.ResponseWriter, r *http.Request) {
	if h.config.IsDev() {
		loadTemplates()
	}

	user := middlewares.GetPrincipal(r)
	if user.StripeCustomerId == "" {
		http.Redirect(w, r, fmt.Sprintf("%s/settings?error=%s#subscription", h.config.Server.BasePath, "no subscription found with your e-mail address, please contact us!"), http.StatusFound)
		return
	}

	portalParams := &stripe.BillingPortalSessionParams{
		Customer:  &user.StripeCustomerId,
		ReturnURL: &h.config.Server.PublicUrl,
	}

	session, err := stripePortalSession.New(portalParams)
	if err != nil {
		conf.Log().Request(r).Error("failed to create stripe portal session: %v", err)
		http.Redirect(w, r, fmt.Sprintf("%s/settings?error=%s#subscription", h.config.Server.BasePath, "something went wrong"), http.StatusFound)
		return
	}

	http.Redirect(w, r, session.URL, http.StatusSeeOther)
}

func (h *SubscriptionHandler) PostWebhook(w http.ResponseWriter, r *http.Request) {
	bodyReader := http.MaxBytesReader(w, r.Body, int64(65536))
	payload, err := ioutil.ReadAll(bodyReader)
	if err != nil {
		conf.Log().Request(r).Error("error in stripe webhook request: %v", err)
		w.WriteHeader(http.StatusServiceUnavailable)
		return
	}

	event, err := webhook.ConstructEventWithOptions(payload, r.Header.Get("Stripe-Signature"), h.config.Subscriptions.StripeEndpointSecret, webhook.ConstructEventOptions{
		IgnoreAPIVersionMismatch: true,
	})
	if err != nil {
		conf.Log().Request(r).Error("stripe webhook signature verification failed: %v", err)
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	switch event.Type {
	case "customer.subscription.deleted",
		"customer.subscription.updated",
		"customer.subscription.created":
		// example payload: https://pastr.de/p/k7bx3alx38b1iawo6amtx09k
		subscription, err := h.parseSubscriptionEvent(w, r, event)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		logbuch.Info("received stripe subscription event of type '%s' for subscription '%s' (customer '%s').", event.Type, subscription.ID, subscription.Customer.ID)

		// first, try to get user by associated customer id (requires checkout.session.completed event to have been processed before)
		user, err := h.userSrvc.GetUserByStripeCustomerId(subscription.Customer.ID)
		if err != nil {
			conf.Log().Request(r).Warn("failed to find user with stripe customer id '%s' to update their subscription (status '%s')", subscription.Customer.ID, subscription.Status)

			// second, resolve customer and try to get user by email
			customer, err := stripeCustomer.Get(subscription.Customer.ID, nil)
			if err != nil {
				conf.Log().Request(r).Error("failed to fetch stripe customer with id '%s', %v", subscription.Customer.ID, err)
				w.WriteHeader(http.StatusInternalServerError)
				return
			}

			u, err := h.userSrvc.GetUserByEmail(customer.Email)
			if err != nil {
				conf.Log().Request(r).Error("failed to get user with email '%s' as stripe customer '%s' for processing event for subscription %s, %v", customer.Email, subscription.Customer.ID, subscription.ID, err)
				w.WriteHeader(http.StatusInternalServerError)
				return
			}
			user = u
		}

		if err := h.handleSubscriptionEvent(subscription, user); err != nil {
			conf.Log().Request(r).Error("failed to handle subscription event %s (%s) for user %s, %v", event.ID, event.Type, user.ID, err)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}

	case "checkout.session.completed":
		// example payload: https://pastr.de/p/d01iniw9naq9hkmvyqtxin2w
		checkoutSession, err := h.parseCheckoutSessionEvent(w, r, event)
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			return
		}
		logbuch.Info("received stripe checkout session event of type '%s' for session '%s' (customer '%s' with email '%s').", event.Type, checkoutSession.ID, checkoutSession.Customer.ID, checkoutSession.CustomerEmail)

		user, err := h.userSrvc.GetUserById(checkoutSession.ClientReferenceID)
		if err != nil {
			conf.Log().Request(r).Error("failed to find user with id '%s' to update associated stripe customer (%s)", user.ID, checkoutSession.Customer.ID)
			w.WriteHeader(http.StatusInternalServerError)
			return
		}

		if user.StripeCustomerId == "" {
			user.StripeCustomerId = checkoutSession.Customer.ID
			if _, err := h.userSrvc.Update(user); err != nil {
				conf.Log().Request(r).Error("failed to update stripe customer id (%s) for user '%s', %v", checkoutSession.Customer.ID, user.ID, err)
			} else {
				logbuch.Info("associated user '%s' with stripe customer '%s'", user.ID, checkoutSession.Customer.ID)
			}
		} else if user.StripeCustomerId != checkoutSession.Customer.ID {
			conf.Log().Request(r).Error("invalid state: tried to associate user '%s' with stripe customer '%s', but '%s' already assigned", user.ID, checkoutSession.Customer.ID, user.StripeCustomerId)
		}

	default:
		logbuch.Warn("got stripe event '%s' with no handler defined", event.Type)
	}

	w.WriteHeader(http.StatusOK)
}

func (h *SubscriptionHandler) GetCheckoutSuccess(w http.ResponseWriter, r *http.Request) {
	http.Redirect(w, r, fmt.Sprintf("%s/settings?success=%s#subscription", h.config.Server.BasePath, "you have successfully subscribed to Wakapi!"), http.StatusFound)
}

func (h *SubscriptionHandler) GetCheckoutCancel(w http.ResponseWriter, r *http.Request) {
	http.Redirect(w, r, fmt.Sprintf("%s/settings#subscription", h.config.Server.BasePath), http.StatusFound)
}

func (h *SubscriptionHandler) handleSubscriptionEvent(subscription *stripe.Subscription, user *models.User) error {
	var hasSubscribed bool

	switch subscription.Status {
	case "active":
		until := models.CustomTime(time.Unix(subscription.CurrentPeriodEnd, 0))

		if user.SubscribedUntil == nil || !user.SubscribedUntil.T().Equal(until.T()) {
			hasSubscribed = true
			user.SubscribedUntil = &until
			logbuch.Info("user %s got active subscription %s until %v", user.ID, subscription.ID, user.SubscribedUntil)
		}

		if cancelAt := time.Unix(subscription.CancelAt, 0); !cancelAt.IsZero() && cancelAt.After(time.Now()) {
			logbuch.Info("user %s chose to cancel subscription %s by %v", user.ID, subscription.ID, cancelAt)
		}
	case "canceled", "unpaid":
		user.SubscribedUntil = nil
		logbuch.Info("user %s's subscription %s got canceled, because of status update to '%s'", user.ID, subscription.ID, subscription.Status)
	default:
		logbuch.Info("got subscription (%s) status update to '%s' for user '%s'", subscription.ID, subscription.Status, user.ID)
		return nil
	}

	_, err := h.userSrvc.Update(user)
	if err == nil && hasSubscribed {
		go h.clearSubscriptionNotificationStatus(user.ID)
	}
	return err
}

func (h *SubscriptionHandler) parseSubscriptionEvent(w http.ResponseWriter, r *http.Request, event stripe.Event) (*stripe.Subscription, error) {
	var subscription stripe.Subscription
	if err := json.Unmarshal(event.Data.Raw, &subscription); err != nil {
		conf.Log().Request(r).Error("failed to parse stripe webhook payload: %v", err)
		w.WriteHeader(http.StatusBadRequest)
		return nil, err
	}
	return &subscription, nil
}

func (h *SubscriptionHandler) parseCheckoutSessionEvent(w http.ResponseWriter, r *http.Request, event stripe.Event) (*stripe.CheckoutSession, error) {
	var checkoutSession stripe.CheckoutSession
	if err := json.Unmarshal(event.Data.Raw, &checkoutSession); err != nil {
		conf.Log().Request(r).Error("failed to parse stripe webhook payload: %v", err)
		w.WriteHeader(http.StatusBadRequest)
		return nil, err
	}

	return &checkoutSession, nil
}

func (h *SubscriptionHandler) findStripeCustomerByEmail(email string) (*stripe.Customer, error) {
	params := &stripe.CustomerSearchParams{
		SearchParams: stripe.SearchParams{
			Query: fmt.Sprintf(`email:"%s"`, email),
		},
	}

	results := stripeCustomer.Search(params)
	if err := results.Err(); err != nil {
		return nil, err
	}

	if results.Next() {
		return results.Customer(), nil
	} else {
		return nil, errors.New("no customer found with given criteria")
	}
}

func (h *SubscriptionHandler) clearSubscriptionNotificationStatus(userId string) {
	key := fmt.Sprintf("%s_%s", conf.KeySubscriptionNotificationSent, userId)
	if err := h.keyValueSrvc.DeleteString(key); err != nil {
		logbuch.Warn("failed to delete '%s', %v", key, err)
	}
}