package handlers

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"log"
	"net/http"
	"strconv"

	"git.nixc.us/a250/ss-atlas/internal/accounts"
	stripego "github.com/stripe/stripe-go/v84"
	"github.com/stripe/stripe-go/v84/webhook"
)

const maxWebhookPayload = 65536

func (a *App) handleWebhook(w http.ResponseWriter, r *http.Request) {
	body, err := io.ReadAll(io.LimitReader(r.Body, maxWebhookPayload))
	if err != nil {
		http.Error(w, "read error", http.StatusBadRequest)
		return
	}

	sig := r.Header.Get("Stripe-Signature")
	event, err := webhook.ConstructEvent(body, sig, a.stripe.WebhookSecret())
	if err != nil {
		log.Printf("webhook signature verification failed: %v", err)
		http.Error(w, "invalid signature", http.StatusUnauthorized)
		return
	}

	switch event.Type {
	case "checkout.session.completed":
		a.onCheckoutCompleted(event)
	case "customer.subscription.deleted":
		a.onSubscriptionDeleted(event)
	case "customer.subscription.updated":
		a.onSubscriptionUpdated(event)
	case "invoice.paid":
		a.onInvoicePaid(event)
	default:
		log.Printf("unhandled webhook event: %s", event.Type)
	}

	w.WriteHeader(http.StatusOK)
}

// Reconciliation backstop: ensures the account, billing link, and instance exist.
func (a *App) onCheckoutCompleted(event stripego.Event) {
	var sess stripego.CheckoutSession
	if err := json.Unmarshal(event.Data.Raw, &sess); err != nil {
		log.Printf("checkout unmarshal error: %v", err)
		return
	}

	email := sess.CustomerDetails.Email
	customerID := sess.Customer.ID
	phone := ""
	domain := ""
	accountID := int64(0)
	if sess.Metadata != nil {
		phone = sess.Metadata["customer_phone"]
		domain = sess.Metadata["customer_domain"]
		accountID, _ = strconv.ParseInt(sess.Metadata["account_id"], 10, 64)
	}

	log.Printf("webhook: checkout completed email=%s customer=%s account_id=%d", email, customerID, accountID)

	if a.cfg.MaxSignups > 0 {
		count, err := a.accounts.CountCustomers(context.Background())
		if err == nil && count >= a.cfg.MaxSignups {
			log.Printf("webhook: signup limit reached (%d), skipping provision for %s", a.cfg.MaxSignups, email)
			return
		}
	}

	_, _, err := a.accounts.UpsertCheckout(context.Background(), accounts.CheckoutInput{
		AccountID:            accountID,
		Email:                email,
		DisplayName:          email,
		Phone:                phone,
		CustomerDomain:       domain,
		StripeCustomerID:     customerID,
		StripeSubscriptionID: subscriptionIDFromSession(&sess),
		StripeSessionID:      sess.ID,
		StripeEventID:        event.ID,
	})
	if err != nil {
		log.Printf("webhook: account ensure failed: %v", err)
	}

	subID := ""
	if sess.Subscription != nil && sess.Subscription.ID != "" {
		subID = sess.Subscription.ID
	} else {
		var raw struct {
			Subscription interface{} `json:"subscription"`
		}
		if json.Unmarshal(event.Data.Raw, &raw) == nil {
			if s, ok := raw.Subscription.(string); ok {
				subID = s
			}
		}
	}
	if subID != "" {
		a.maybeScheduleFreeTierCancel(subID)
	}
}

func (a *App) onSubscriptionDeleted(event stripego.Event) {
	var sub stripego.Subscription
	if err := json.Unmarshal(event.Data.Raw, &sub); err != nil {
		log.Printf("subscription unmarshal error: %v", err)
		return
	}

	customerID := sub.Customer.ID
	log.Printf("subscription deleted for customer %s", customerID)

	_, inst, err := a.accounts.AccountByStripeCustomerID(context.Background(), customerID)
	if err != nil {
		log.Printf("could not find account for customer %s: %v", customerID, err)
		return
	}

	if err := a.accounts.MarkSubscriptionStatus(context.Background(), customerID, "cancelled"); err != nil && !errors.Is(err, accounts.ErrNotFound) {
		log.Printf("subscription status update failed: %v", err)
	}

	if err := a.swarm.ArchiveVolumes(inst.StackName, a.cfg.ArchivePath); err != nil {
		log.Printf("archive failed for %s: %v", inst.StackName, err)
	}

	if err := a.swarm.RemoveStack(inst.StackName); err != nil {
		log.Printf("stack remove failed for %s: %v", inst.StackName, err)
	}
	_ = a.accounts.UpdateInstanceState(context.Background(), inst.StackName, "archived", false)

	log.Printf("deprovisioned stack for customer %s (%s), volumes archived", customerID, inst.Slug)
}

func (a *App) onSubscriptionUpdated(event stripego.Event) {
	var sub stripego.Subscription
	if err := json.Unmarshal(event.Data.Raw, &sub); err != nil {
		log.Printf("subscription update unmarshal error: %v", err)
		return
	}

	if sub.Status == stripego.SubscriptionStatusCanceled ||
		sub.Status == stripego.SubscriptionStatusUnpaid {
		if sub.Customer != nil && sub.Customer.ID != "" {
			_ = a.accounts.MarkSubscriptionStatus(context.Background(), sub.Customer.ID, string(sub.Status))
		}
		log.Printf("subscription %s status=%s, will be cleaned up on deletion", sub.ID, sub.Status)
	}
}