Asynchronous Processing

package main

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

const webhookSignatureKey = "YOUR_WEBHOOK_SECRET_FROM_ADMIN_CONSOLE"

// NutritionRecord represents the webhook payload structure
type NutritionRecord struct {
	ApplicationID int64     `json:"application_id"`
	UID           string    `json:"uid"`
	RecordID      string    `json:"record_id"`
	Status        string    `json:"status"`
	DishName      string    `json:"dish_name"`
	NutriScore    string    `json:"nutri_score"`
	UploadedAt    time.Time `json:"uploaded_at"`
	ModifiedAt    time.Time `json:"modified_at"`
	// Add other fields as needed
}

func main() {
	http.HandleFunc("/nutrition-webhook", func(w http.ResponseWriter, r *http.Request) {
		// Verify HMAC signature
		signature := r.Header.Get("x-body-signature")
		if signature == "" {
			http.Error(w, "Missing signature", http.StatusBadRequest)
			return
		}

		// Read request body
		body, err := io.ReadAll(r.Body)
		if err != nil {
			http.Error(w, "Failed to read body", http.StatusInternalServerError)
			return
		}

		// Calculate and verify HMAC
		hm := hmac.New(sha256.New, []byte(webhookSignatureKey))
		hm.Write(body)
		expectedSignature := hex.EncodeToString(hm.Sum(nil))
		
		if signature != expectedSignature {
			http.Error(w, "Invalid signature", http.StatusUnauthorized)
			return
		}

		// Parse nutrition record
		var record NutritionRecord
		if err := json.Unmarshal(body, &record); err != nil {
			http.Error(w, "Invalid JSON", http.StatusBadRequest)
			return
		}

		// Process the nutrition record
		fmt.Printf("Received nutrition analysis: %s for user %s\n", record.Status, record.UID)
		if record.Status == "completed" {
			fmt.Printf("Dish: %s, Nutri-Score: %s\n", record.DishName, record.NutriScore)
			// Update your application with the results
		} else if record.Status == "failed" {
			fmt.Printf("Analysis failed for record %s\n", record.RecordID)
			// Handle failure case
		}

		// Respond with success
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("OK"))
	})

	fmt.Println("Starting nutrition webhook server on port 8000")
	http.ListenAndServe(":8000", nil)
}