package main

import (
	"fmt"
	"net/http"
	"os"
	"strings"
)

func getClientIP(r *http.Request) string {
	// Check common headers for real client IP
	if ip := r.Header.Get("X-Real-Ip"); ip != "" {
		return ip
	}
	if forwardedFor := r.Header.Get("X-Forwarded-For"); forwardedFor != "" {
		ips := strings.Split(forwardedFor, ",")
		return strings.TrimSpace(ips[0])
	}
	// Fallback to remote address
	return r.RemoteAddr
}

func handler(w http.ResponseWriter, r *http.Request) {
	// Set content type
	w.Header().Set("Content-Type", "text/plain")

	// Get client IP
	clientIP := getClientIP(r)

	// Write response
	fmt.Fprintf(w, "Request IP: %s\n", clientIP)
	fmt.Fprintln(w, "Headers:")

	for name, values := range r.Header {
		for _, value := range values {
			fmt.Fprintf(w, "%s: %s\n", name, value)
		}
	}
}

func main() {
	// Get the listen address from the environment variable or use default
	listenAddr := os.Getenv("LISTEN")
	if listenAddr == "" {
		listenAddr = "0.0.0.0:8080"
	}

	http.HandleFunc("/", handler)

	fmt.Printf("Starting server on %s\n", listenAddr)
	if err := http.ListenAndServe(listenAddr, nil); err != nil {
		fmt.Printf("Error starting server: %s\n", err)
	}
}