http-nats-proxy/main.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"strings"
	"time"

	"github.com/nats-io/nats.go"
)

func main() {
	// Connect to NATS server
	nc, err := nats.Connect(nats.DefaultURL)
	if err != nil {
		log.Fatal(err)
	}
	defer nc.Close()

	// HTTP handler function
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		// Read the request body
		body, err := ioutil.ReadAll(r.Body)
		if err != nil {
			http.Error(w, "Error reading request body", http.StatusInternalServerError)
			return
		}
		defer r.Body.Close()

		// Drop the leading slash if there is one, and replace slashes with dots.
		subject := strings.ReplaceAll(strings.TrimPrefix(r.URL.Path, "/"), "/", ".")

		// Create a NATS message with the request body and headers
		msg := nats.Msg{
			Subject: fmt.Sprintf("http.%s", subject),
			Data:    body,
			Header:  nats.Header{},
		}
		log.Println("subject:", msg.Subject)

		// Copy HTTP headers to NATS message headers
		for key, values := range r.Header {
			for _, value := range values {
				msg.Header.Add(key, value)
			}
		}

		// Send request to NATS and wait for reply
		reply, err := nc.RequestMsg(&msg, 30*time.Second)
		if err != nil {
			http.Error(w, "Error processing request", http.StatusInternalServerError)
			log.Println("Error processing the request", err)
			return
		}

		// Copy NATS reply headers to HTTP response
		for key, values := range reply.Header {
			for _, value := range values {
				w.Header().Add(key, value)
			}
		}

		// Write NATS reply body to HTTP response
		w.Write(reply.Data)
	})

	// Start HTTP server
	fmt.Println("Server is running on http://localhost:8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}