server.go

package main

import (
	"encoding/json"
	"log"
	"net/http"
)

// RunServer starts a simple HTTP API for subnet calculations.
// Endpoints:
//
//	GET /api/subnet?cidr=<ip/prefix>
//
// Example:
//
//	curl 'http://localhost:8080/api/subnet?cidr=192.168.1.10/26'
func RunServer(addr string) error {
	mux := http.NewServeMux()
	mux.HandleFunc("/api/subnet", func(w http.ResponseWriter, r *http.Request) {
		// Basic CORS for local dev
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
		w.Header().Set("Access-Control-Allow-Methods", "GET, OPTIONS")
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}

		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}

		cidr := r.URL.Query().Get("cidr")
		if cidr == "" {
			http.Error(w, "missing cidr query param", http.StatusBadRequest)
			return
		}

    s := Subnet{ip: cidr}
    address, prefix, total, networks, hosts, broadcasts, err := s.calc(cidr)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}

		resp := map[string]interface{}{
			"address":    address,
			"prefix":     prefix,
			"total":      total,
			"networks":   networks,
			"hosts":      hosts,
			"broadcasts": broadcasts,
		}

		// Add detailed fields while keeping existing keys for compatibility
		if a, p, mask, wildcard, netAddr, first, last, bcast, usable, _, derr := computeDetails(cidr); derr == nil {
			resp["prefix"] = p // keep prefix consistent
			resp["subnetMask"] = mask
			resp["wildcardMask"] = wildcard
			resp["network"] = netAddr
			resp["firstHost"] = first
			resp["lastHost"] = last
			resp["broadcast"] = bcast
			resp["usableHosts"] = usable
			_ = a // already included as address
		}
		w.Header().Set("Content-Type", "application/json")
		if err := json.NewEncoder(w).Encode(resp); err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
	})

	log.Printf("subnet API listening on %s\n", addr)
	log.Printf("try: http://localhost%[1]s/api/subnet?cidr=192.168.1.10/26\n", addr)
	return http.ListenAndServe(addr, mux)
}