honeyDueAPI/internal/handlers/subscription_webhook_handler.go

package handlers

import (
	"crypto/ecdsa"
	"crypto/x509"
	"encoding/base64"
	"encoding/json"
	"encoding/pem"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"

	"github.com/treytartt/casera-api/internal/config"
	"github.com/treytartt/casera-api/internal/models"
	"github.com/treytartt/casera-api/internal/repositories"
)

// SubscriptionWebhookHandler handles subscription webhook callbacks
type SubscriptionWebhookHandler struct {
	subscriptionRepo *repositories.SubscriptionRepository
	userRepo         *repositories.UserRepository
	appleRootCerts   []*x509.Certificate
}

// NewSubscriptionWebhookHandler creates a new webhook handler
func NewSubscriptionWebhookHandler(
	subscriptionRepo *repositories.SubscriptionRepository,
	userRepo *repositories.UserRepository,
) *SubscriptionWebhookHandler {
	return &SubscriptionWebhookHandler{
		subscriptionRepo: subscriptionRepo,
		userRepo:         userRepo,
	}
}

// ====================
// Apple App Store Server Notifications v2
// ====================

// AppleNotificationPayload represents the outer signed payload from Apple
type AppleNotificationPayload struct {
	SignedPayload string `json:"signedPayload"`
}

// AppleNotificationData represents the decoded notification data
type AppleNotificationData struct {
	NotificationType    string                      `json:"notificationType"`
	Subtype             string                      `json:"subtype"`
	NotificationUUID    string                      `json:"notificationUUID"`
	Data                AppleNotificationDataInner  `json:"data"`
	Version             string                      `json:"version"`
	SignedDate          int64                       `json:"signedDate"`
}

// AppleNotificationDataInner contains the transaction details
type AppleNotificationDataInner struct {
	AppAppleID            int64  `json:"appAppleId"`
	BundleID              string `json:"bundleId"`
	BundleVersion         string `json:"bundleVersion"`
	Environment           string `json:"environment"`
	SignedTransactionInfo string `json:"signedTransactionInfo"`
	SignedRenewalInfo     string `json:"signedRenewalInfo"`
}

// AppleTransactionInfo represents decoded transaction info
type AppleTransactionInfo struct {
	TransactionID         string `json:"transactionId"`
	OriginalTransactionID string `json:"originalTransactionId"`
	ProductID             string `json:"productId"`
	PurchaseDate          int64  `json:"purchaseDate"`
	ExpiresDate           int64  `json:"expiresDate"`
	Type                  string `json:"type"`
	AppAccountToken       string `json:"appAccountToken"` // Your user ID if set during purchase
	BundleID              string `json:"bundleId"`
	Environment           string `json:"environment"`
	RevocationDate        *int64 `json:"revocationDate,omitempty"`
	RevocationReason      *int   `json:"revocationReason,omitempty"`
}

// AppleRenewalInfo represents subscription renewal info
type AppleRenewalInfo struct {
	AutoRenewProductID string `json:"autoRenewProductId"`
	AutoRenewStatus    int    `json:"autoRenewStatus"` // 1 = will renew, 0 = turned off
	ExpirationIntent   int    `json:"expirationIntent"`
	IsInBillingRetry   bool   `json:"isInBillingRetryPeriod"`
}

// HandleAppleWebhook handles POST /api/subscription/webhook/apple/
func (h *SubscriptionWebhookHandler) HandleAppleWebhook(c *gin.Context) {
	body, err := io.ReadAll(c.Request.Body)
	if err != nil {
		log.Printf("Apple Webhook: Failed to read body: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "failed to read request body"})
		return
	}

	var payload AppleNotificationPayload
	if err := json.Unmarshal(body, &payload); err != nil {
		log.Printf("Apple Webhook: Failed to parse payload: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid payload"})
		return
	}

	// Decode and verify the signed payload (JWS)
	notification, err := h.decodeAppleSignedPayload(payload.SignedPayload)
	if err != nil {
		log.Printf("Apple Webhook: Failed to decode signed payload: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid signed payload"})
		return
	}

	log.Printf("Apple Webhook: Received %s (subtype: %s) for bundle %s",
		notification.NotificationType, notification.Subtype, notification.Data.BundleID)

	// Verify bundle ID matches our app
	cfg := config.Get()
	if cfg != nil && cfg.AppleIAP.BundleID != "" {
		if notification.Data.BundleID != cfg.AppleIAP.BundleID {
			log.Printf("Apple Webhook: Bundle ID mismatch: got %s, expected %s",
				notification.Data.BundleID, cfg.AppleIAP.BundleID)
			c.JSON(http.StatusBadRequest, gin.H{"error": "bundle ID mismatch"})
			return
		}
	}

	// Decode transaction info
	transactionInfo, err := h.decodeAppleTransaction(notification.Data.SignedTransactionInfo)
	if err != nil {
		log.Printf("Apple Webhook: Failed to decode transaction: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid transaction info"})
		return
	}

	// Decode renewal info if present
	var renewalInfo *AppleRenewalInfo
	if notification.Data.SignedRenewalInfo != "" {
		renewalInfo, _ = h.decodeAppleRenewalInfo(notification.Data.SignedRenewalInfo)
	}

	// Process the notification
	if err := h.processAppleNotification(notification, transactionInfo, renewalInfo); err != nil {
		log.Printf("Apple Webhook: Failed to process notification: %v", err)
		// Still return 200 to prevent Apple from retrying
	}

	// Always return 200 OK to acknowledge receipt
	c.JSON(http.StatusOK, gin.H{"status": "received"})
}

// decodeAppleSignedPayload decodes and verifies an Apple JWS payload
func (h *SubscriptionWebhookHandler) decodeAppleSignedPayload(signedPayload string) (*AppleNotificationData, error) {
	// JWS format: header.payload.signature
	parts := strings.Split(signedPayload, ".")
	if len(parts) != 3 {
		return nil, fmt.Errorf("invalid JWS format")
	}

	// Decode payload (we're trusting Apple's signature for now)
	// In production, you should verify the signature using Apple's root certificate
	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
	if err != nil {
		return nil, fmt.Errorf("failed to decode payload: %w", err)
	}

	var notification AppleNotificationData
	if err := json.Unmarshal(payload, &notification); err != nil {
		return nil, fmt.Errorf("failed to parse notification: %w", err)
	}

	return &notification, nil
}

// decodeAppleTransaction decodes a signed transaction info JWS
func (h *SubscriptionWebhookHandler) decodeAppleTransaction(signedTransaction string) (*AppleTransactionInfo, error) {
	parts := strings.Split(signedTransaction, ".")
	if len(parts) != 3 {
		return nil, fmt.Errorf("invalid JWS format")
	}

	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
	if err != nil {
		return nil, fmt.Errorf("failed to decode payload: %w", err)
	}

	var info AppleTransactionInfo
	if err := json.Unmarshal(payload, &info); err != nil {
		return nil, fmt.Errorf("failed to parse transaction info: %w", err)
	}

	return &info, nil
}

// decodeAppleRenewalInfo decodes signed renewal info JWS
func (h *SubscriptionWebhookHandler) decodeAppleRenewalInfo(signedRenewal string) (*AppleRenewalInfo, error) {
	parts := strings.Split(signedRenewal, ".")
	if len(parts) != 3 {
		return nil, fmt.Errorf("invalid JWS format")
	}

	payload, err := base64.RawURLEncoding.DecodeString(parts[1])
	if err != nil {
		return nil, fmt.Errorf("failed to decode payload: %w", err)
	}

	var info AppleRenewalInfo
	if err := json.Unmarshal(payload, &info); err != nil {
		return nil, fmt.Errorf("failed to parse renewal info: %w", err)
	}

	return &info, nil
}

// processAppleNotification handles the business logic for Apple notifications
func (h *SubscriptionWebhookHandler) processAppleNotification(
	notification *AppleNotificationData,
	transaction *AppleTransactionInfo,
	renewal *AppleRenewalInfo,
) error {
	// Find user by stored receipt data (original transaction ID)
	user, err := h.findUserByAppleTransaction(transaction.OriginalTransactionID)
	if err != nil {
		log.Printf("Apple Webhook: Could not find user for transaction %s: %v",
			transaction.OriginalTransactionID, err)
		// Not an error - might be a transaction we don't track
		return nil
	}

	log.Printf("Apple Webhook: Processing %s for user %d (product: %s)",
		notification.NotificationType, user.ID, transaction.ProductID)

	switch notification.NotificationType {
	case "SUBSCRIBED":
		// New subscription or resubscription
		return h.handleAppleSubscribed(user.ID, transaction, renewal)

	case "DID_RENEW":
		// Subscription successfully renewed
		return h.handleAppleRenewed(user.ID, transaction, renewal)

	case "DID_CHANGE_RENEWAL_STATUS":
		// User turned auto-renew on/off
		return h.handleAppleRenewalStatusChange(user.ID, transaction, renewal)

	case "DID_FAIL_TO_RENEW":
		// Billing issue - subscription may still be in grace period
		return h.handleAppleFailedToRenew(user.ID, transaction, renewal)

	case "EXPIRED":
		// Subscription expired
		return h.handleAppleExpired(user.ID, transaction)

	case "REFUND":
		// User got a refund
		return h.handleAppleRefund(user.ID, transaction)

	case "REVOKE":
		// Family sharing revoked or refund
		return h.handleAppleRevoke(user.ID, transaction)

	case "GRACE_PERIOD_EXPIRED":
		// Grace period ended without successful billing
		return h.handleAppleGracePeriodExpired(user.ID, transaction)

	default:
		log.Printf("Apple Webhook: Unhandled notification type: %s", notification.NotificationType)
	}

	return nil
}

func (h *SubscriptionWebhookHandler) findUserByAppleTransaction(originalTransactionID string) (*models.User, error) {
	// Look up user subscription by stored receipt data
	subscription, err := h.subscriptionRepo.FindByAppleReceiptContains(originalTransactionID)
	if err != nil {
		return nil, err
	}

	user, err := h.userRepo.FindByID(subscription.UserID)
	if err != nil {
		return nil, err
	}

	return user, nil
}

func (h *SubscriptionWebhookHandler) handleAppleSubscribed(userID uint, tx *AppleTransactionInfo, renewal *AppleRenewalInfo) error {
	expiresAt := time.Unix(tx.ExpiresDate/1000, 0)
	autoRenew := renewal != nil && renewal.AutoRenewStatus == 1

	if err := h.subscriptionRepo.UpgradeToPro(userID, expiresAt, "ios"); err != nil {
		return err
	}
	if err := h.subscriptionRepo.SetAutoRenew(userID, autoRenew); err != nil {
		return err
	}

	log.Printf("Apple Webhook: User %d subscribed, expires %v, autoRenew=%v", userID, expiresAt, autoRenew)
	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleRenewed(userID uint, tx *AppleTransactionInfo, renewal *AppleRenewalInfo) error {
	expiresAt := time.Unix(tx.ExpiresDate/1000, 0)

	if err := h.subscriptionRepo.UpgradeToPro(userID, expiresAt, "ios"); err != nil {
		return err
	}

	log.Printf("Apple Webhook: User %d renewed, new expiry %v", userID, expiresAt)
	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleRenewalStatusChange(userID uint, tx *AppleTransactionInfo, renewal *AppleRenewalInfo) error {
	if renewal == nil {
		return nil
	}

	autoRenew := renewal.AutoRenewStatus == 1
	if err := h.subscriptionRepo.SetAutoRenew(userID, autoRenew); err != nil {
		return err
	}

	if !autoRenew {
		// User turned off auto-renew (will cancel at end of period)
		now := time.Now().UTC()
		if err := h.subscriptionRepo.SetCancelledAt(userID, now); err != nil {
			return err
		}
		log.Printf("Apple Webhook: User %d turned off auto-renew, will expire at end of period", userID)
	} else {
		// User turned auto-renew back on
		if err := h.subscriptionRepo.ClearCancelledAt(userID); err != nil {
			return err
		}
		log.Printf("Apple Webhook: User %d turned auto-renew back on", userID)
	}

	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleFailedToRenew(userID uint, tx *AppleTransactionInfo, renewal *AppleRenewalInfo) error {
	// Subscription is in billing retry or grace period
	log.Printf("Apple Webhook: User %d failed to renew, may be in grace period", userID)
	// Don't downgrade yet - Apple may retry billing
	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleExpired(userID uint, tx *AppleTransactionInfo) error {
	if err := h.subscriptionRepo.DowngradeToFree(userID); err != nil {
		return err
	}

	log.Printf("Apple Webhook: User %d subscription expired, downgraded to free", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleRefund(userID uint, tx *AppleTransactionInfo) error {
	if err := h.subscriptionRepo.DowngradeToFree(userID); err != nil {
		return err
	}

	log.Printf("Apple Webhook: User %d got refund, downgraded to free", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleRevoke(userID uint, tx *AppleTransactionInfo) error {
	if err := h.subscriptionRepo.DowngradeToFree(userID); err != nil {
		return err
	}

	log.Printf("Apple Webhook: User %d subscription revoked, downgraded to free", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleAppleGracePeriodExpired(userID uint, tx *AppleTransactionInfo) error {
	if err := h.subscriptionRepo.DowngradeToFree(userID); err != nil {
		return err
	}

	log.Printf("Apple Webhook: User %d grace period expired, downgraded to free", userID)
	return nil
}

// ====================
// Google Real-time Developer Notifications
// ====================

// GoogleNotification represents a Google Pub/Sub push message
type GoogleNotification struct {
	Message      GooglePubSubMessage `json:"message"`
	Subscription string              `json:"subscription"`
}

// GooglePubSubMessage represents the Pub/Sub message wrapper
type GooglePubSubMessage struct {
	Data        string            `json:"data"` // Base64 encoded
	MessageID   string            `json:"messageId"`
	PublishTime string            `json:"publishTime"`
	Attributes  map[string]string `json:"attributes"`
}

// GoogleDeveloperNotification represents the decoded notification
type GoogleDeveloperNotification struct {
	Version                  string                          `json:"version"`
	PackageName              string                          `json:"packageName"`
	EventTimeMillis          string                          `json:"eventTimeMillis"`
	SubscriptionNotification *GoogleSubscriptionNotification `json:"subscriptionNotification"`
	OneTimeProductNotification *GoogleOneTimeNotification    `json:"oneTimeProductNotification"`
	TestNotification         *GoogleTestNotification         `json:"testNotification"`
}

// GoogleSubscriptionNotification represents subscription-specific data
type GoogleSubscriptionNotification struct {
	Version          string `json:"version"`
	NotificationType int    `json:"notificationType"`
	PurchaseToken    string `json:"purchaseToken"`
	SubscriptionID   string `json:"subscriptionId"`
}

// GoogleOneTimeNotification represents one-time purchase data
type GoogleOneTimeNotification struct {
	Version          string `json:"version"`
	NotificationType int    `json:"notificationType"`
	PurchaseToken    string `json:"purchaseToken"`
	SKU              string `json:"sku"`
}

// GoogleTestNotification represents a test notification
type GoogleTestNotification struct {
	Version string `json:"version"`
}

// Google subscription notification types
const (
	GoogleSubRecovered            = 1  // Subscription recovered from account hold
	GoogleSubRenewed              = 2  // Active subscription renewed
	GoogleSubCanceled             = 3  // Subscription was cancelled (voluntary or involuntary)
	GoogleSubPurchased            = 4  // New subscription purchased
	GoogleSubOnHold               = 5  // Subscription entered account hold
	GoogleSubInGracePeriod        = 6  // Subscription entered grace period
	GoogleSubRestarted            = 7  // User reactivated subscription
	GoogleSubPriceChangeConfirmed = 8  // Price change confirmed by user
	GoogleSubDeferred             = 9  // Subscription deferred
	GoogleSubPaused               = 10 // Subscription paused
	GoogleSubPauseScheduleChanged = 11 // Pause schedule changed
	GoogleSubRevoked              = 12 // Subscription revoked
	GoogleSubExpired              = 13 // Subscription expired
)

// HandleGoogleWebhook handles POST /api/subscription/webhook/google/
func (h *SubscriptionWebhookHandler) HandleGoogleWebhook(c *gin.Context) {
	body, err := io.ReadAll(c.Request.Body)
	if err != nil {
		log.Printf("Google Webhook: Failed to read body: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "failed to read request body"})
		return
	}

	var notification GoogleNotification
	if err := json.Unmarshal(body, &notification); err != nil {
		log.Printf("Google Webhook: Failed to parse notification: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid notification"})
		return
	}

	// Decode the base64 data
	data, err := base64.StdEncoding.DecodeString(notification.Message.Data)
	if err != nil {
		log.Printf("Google Webhook: Failed to decode message data: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid message data"})
		return
	}

	var devNotification GoogleDeveloperNotification
	if err := json.Unmarshal(data, &devNotification); err != nil {
		log.Printf("Google Webhook: Failed to parse developer notification: %v", err)
		c.JSON(http.StatusBadRequest, gin.H{"error": "invalid developer notification"})
		return
	}

	// Handle test notification
	if devNotification.TestNotification != nil {
		log.Printf("Google Webhook: Received test notification")
		c.JSON(http.StatusOK, gin.H{"status": "test received"})
		return
	}

	// Verify package name
	cfg := config.Get()
	if cfg != nil && cfg.GoogleIAP.PackageName != "" {
		if devNotification.PackageName != cfg.GoogleIAP.PackageName {
			log.Printf("Google Webhook: Package name mismatch: got %s, expected %s",
				devNotification.PackageName, cfg.GoogleIAP.PackageName)
			c.JSON(http.StatusBadRequest, gin.H{"error": "package name mismatch"})
			return
		}
	}

	// Process subscription notification
	if devNotification.SubscriptionNotification != nil {
		if err := h.processGoogleSubscriptionNotification(devNotification.SubscriptionNotification); err != nil {
			log.Printf("Google Webhook: Failed to process notification: %v", err)
			// Still return 200 to acknowledge
		}
	}

	// Acknowledge the message
	c.JSON(http.StatusOK, gin.H{"status": "received"})
}

// processGoogleSubscriptionNotification handles Google subscription events
func (h *SubscriptionWebhookHandler) processGoogleSubscriptionNotification(notification *GoogleSubscriptionNotification) error {
	// Find user by purchase token
	user, err := h.findUserByGoogleToken(notification.PurchaseToken)
	if err != nil {
		log.Printf("Google Webhook: Could not find user for token: %v", err)
		return nil // Not an error - might be unknown token
	}

	log.Printf("Google Webhook: Processing type %d for user %d (subscription: %s)",
		notification.NotificationType, user.ID, notification.SubscriptionID)

	switch notification.NotificationType {
	case GoogleSubPurchased:
		return h.handleGooglePurchased(user.ID, notification)

	case GoogleSubRenewed:
		return h.handleGoogleRenewed(user.ID, notification)

	case GoogleSubRecovered:
		return h.handleGoogleRecovered(user.ID, notification)

	case GoogleSubCanceled:
		return h.handleGoogleCanceled(user.ID, notification)

	case GoogleSubOnHold:
		return h.handleGoogleOnHold(user.ID, notification)

	case GoogleSubInGracePeriod:
		return h.handleGoogleGracePeriod(user.ID, notification)

	case GoogleSubRestarted:
		return h.handleGoogleRestarted(user.ID, notification)

	case GoogleSubRevoked:
		return h.handleGoogleRevoked(user.ID, notification)

	case GoogleSubExpired:
		return h.handleGoogleExpired(user.ID, notification)

	case GoogleSubPaused:
		return h.handleGooglePaused(user.ID, notification)

	default:
		log.Printf("Google Webhook: Unhandled notification type: %d", notification.NotificationType)
	}

	return nil
}

func (h *SubscriptionWebhookHandler) findUserByGoogleToken(purchaseToken string) (*models.User, error) {
	subscription, err := h.subscriptionRepo.FindByGoogleToken(purchaseToken)
	if err != nil {
		return nil, err
	}

	user, err := h.userRepo.FindByID(subscription.UserID)
	if err != nil {
		return nil, err
	}

	return user, nil
}

func (h *SubscriptionWebhookHandler) handleGooglePurchased(userID uint, notification *GoogleSubscriptionNotification) error {
	// New subscription - we should have already processed this via the client
	// This is a backup notification
	log.Printf("Google Webhook: User %d purchased subscription %s", userID, notification.SubscriptionID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleRenewed(userID uint, notification *GoogleSubscriptionNotification) error {
	// Need to query Google API for new expiry date
	// For now, extend by typical period (1 month for monthly, 1 year for yearly)
	var extension time.Duration
	if strings.Contains(notification.SubscriptionID, "monthly") {
		extension = 30 * 24 * time.Hour
	} else {
		extension = 365 * 24 * time.Hour
	}

	newExpiry := time.Now().UTC().Add(extension)
	if err := h.subscriptionRepo.UpgradeToPro(userID, newExpiry, "android"); err != nil {
		return err
	}

	log.Printf("Google Webhook: User %d renewed, extended to %v", userID, newExpiry)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleRecovered(userID uint, notification *GoogleSubscriptionNotification) error {
	// Subscription recovered from account hold - reactivate
	newExpiry := time.Now().UTC().AddDate(0, 1, 0) // 1 month from now
	if err := h.subscriptionRepo.UpgradeToPro(userID, newExpiry, "android"); err != nil {
		return err
	}

	log.Printf("Google Webhook: User %d subscription recovered", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleCanceled(userID uint, notification *GoogleSubscriptionNotification) error {
	// User canceled - will expire at end of period
	now := time.Now().UTC()
	if err := h.subscriptionRepo.SetCancelledAt(userID, now); err != nil {
		return err
	}
	if err := h.subscriptionRepo.SetAutoRenew(userID, false); err != nil {
		return err
	}

	log.Printf("Google Webhook: User %d canceled, will expire at end of period", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleOnHold(userID uint, notification *GoogleSubscriptionNotification) error {
	// Account hold - payment issue, may recover
	log.Printf("Google Webhook: User %d subscription on hold", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleGracePeriod(userID uint, notification *GoogleSubscriptionNotification) error {
	// In grace period - user still has access but billing failed
	log.Printf("Google Webhook: User %d in grace period", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleRestarted(userID uint, notification *GoogleSubscriptionNotification) error {
	// User restarted subscription
	newExpiry := time.Now().UTC().AddDate(0, 1, 0)
	if err := h.subscriptionRepo.UpgradeToPro(userID, newExpiry, "android"); err != nil {
		return err
	}
	if err := h.subscriptionRepo.ClearCancelledAt(userID); err != nil {
		return err
	}
	if err := h.subscriptionRepo.SetAutoRenew(userID, true); err != nil {
		return err
	}

	log.Printf("Google Webhook: User %d restarted subscription", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleRevoked(userID uint, notification *GoogleSubscriptionNotification) error {
	// Subscription revoked - immediate downgrade
	if err := h.subscriptionRepo.DowngradeToFree(userID); err != nil {
		return err
	}

	log.Printf("Google Webhook: User %d subscription revoked", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGoogleExpired(userID uint, notification *GoogleSubscriptionNotification) error {
	// Subscription expired
	if err := h.subscriptionRepo.DowngradeToFree(userID); err != nil {
		return err
	}

	log.Printf("Google Webhook: User %d subscription expired", userID)
	return nil
}

func (h *SubscriptionWebhookHandler) handleGooglePaused(userID uint, notification *GoogleSubscriptionNotification) error {
	// Subscription paused by user
	log.Printf("Google Webhook: User %d subscription paused", userID)
	return nil
}

// ====================
// Signature Verification (Optional but Recommended)
// ====================

// VerifyAppleSignature verifies the JWS signature using Apple's root certificate
// This is optional but recommended for production
func (h *SubscriptionWebhookHandler) VerifyAppleSignature(signedPayload string) error {
	// Load Apple's root certificate if not already loaded
	if h.appleRootCerts == nil {
		// Apple's root certificates can be downloaded from:
		// https://www.apple.com/certificateauthority/
		// You'd typically embed these or load from a file
		return nil // Skip verification for now
	}

	// Parse the JWS token
	token, err := jwt.Parse(signedPayload, func(token *jwt.Token) (interface{}, error) {
		// Get the x5c header (certificate chain)
		x5c, ok := token.Header["x5c"].([]interface{})
		if !ok || len(x5c) == 0 {
			return nil, fmt.Errorf("missing x5c header")
		}

		// Decode the first certificate (leaf)
		certData, err := base64.StdEncoding.DecodeString(x5c[0].(string))
		if err != nil {
			return nil, fmt.Errorf("failed to decode certificate: %w", err)
		}

		cert, err := x509.ParseCertificate(certData)
		if err != nil {
			return nil, fmt.Errorf("failed to parse certificate: %w", err)
		}

		// Verify the certificate chain (simplified)
		// In production, you should verify the full chain

		return cert.PublicKey.(*ecdsa.PublicKey), nil
	})

	if err != nil {
		return fmt.Errorf("failed to verify signature: %w", err)
	}

	if !token.Valid {
		return fmt.Errorf("invalid token")
	}

	return nil
}

// VerifyGooglePubSubToken verifies the Pub/Sub push token (if configured)
func (h *SubscriptionWebhookHandler) VerifyGooglePubSubToken(c *gin.Context) bool {
	// If you configured a push endpoint with authentication, verify here
	// The token is typically in the Authorization header

	// For now, we rely on the endpoint being protected by your infrastructure
	// (e.g., only accessible from Google's IP ranges)
	return true
}

// Helper function to load Apple root certificates from file
func loadAppleRootCertificates(certPath string) ([]*x509.Certificate, error) {
	data, err := os.ReadFile(certPath)
	if err != nil {
		return nil, err
	}

	var certs []*x509.Certificate
	for {
		block, rest := pem.Decode(data)
		if block == nil {
			break
		}
		if block.Type == "CERTIFICATE" {
			cert, err := x509.ParseCertificate(block.Bytes)
			if err != nil {
				return nil, err
			}
			certs = append(certs, cert)
		}
		data = rest
	}

	return certs, nil
}