func Serve()

in serve.go [33:124]
68 lines of code
11 McCabe index (conditional complexity)

func Serve(olarisDir string, args []string) error {
	flag := flag.NewFlagSet("serve", flag.ExitOnError)
	flag.Usage = func() {
		fmt.Println(`Serve a local directory on http://localhost:9768. You can change port with the OPS_PORT environment variable.

Usage:
  ops -serve [options] <dir>

Options:
  -h, --help Print help message
  --no-open Do not open browser automatically
  --proxy <proxy> Use proxy server
		`)
	}
	// Define command line flags

	var helpFlag bool
	var noBrowserFlag bool
	var proxyFlag string

	flag.BoolVar(&helpFlag, "h", false, "Print help message")
	flag.BoolVar(&helpFlag, "help", false, "Print help message")
	flag.BoolVar(&noBrowserFlag, "no-open", false, "Do not open browser")
	flag.StringVar(&proxyFlag, "proxy", "", "Use proxy server")

	// Parse command line flags
	os.Args = args
	err := flag.Parse(os.Args[1:])
	if err != nil {
		return err
	}

	// Print help message if requested
	if flag.NArg() != 1 || helpFlag {
		flag.Usage()
		return nil
	}

	webDir := flag.Arg(0)

	// run ops server and open browser
	port := getOpsPort()
	webDirPath := joinpath(os.Getenv("OPS_PWD"), webDir)
	log.Println("Serving directory: " + webDirPath)

	if !noBrowserFlag {
		if err := browser.OpenURL("http://localhost:" + port); err != nil {
			return err
		}
	}

	localHandler := webFileServerHandler(webDirPath)

	var proxy *httputil.ReverseProxy = nil
	if proxyFlag != "" {
		remoteUrl, err := url.Parse(proxyFlag)
		if err != nil {
			return err
		}
		proxy = httputil.NewSingleHostReverseProxy(remoteUrl)
	}

	customHandler := func(w http.ResponseWriter, r *http.Request) {
		// Check if the file exists locally

		_, err := http.Dir(webDirPath).Open(r.URL.Path)
		if err == nil {
			// Serve the file using the file server
			localHandler.ServeHTTP(w, r)
			return
		}

		// File not found locally, proxy the request to the remote server
		log.Printf("not found locally %s\n", r.URL.Path)

		if proxy != nil {
			log.Printf("Proxying to %s\n", proxyFlag)
			proxy.ServeHTTP(w, r)
		}
	}

	handler := http.HandlerFunc(customHandler)

	if checkPortAvailable(port) {
		log.Println("OpenServerless config server started at http://localhost:" + port)
		addr := fmt.Sprintf(":%s", port)
		return http.ListenAndServe(addr, handler)
	} else {
		log.Println("OpenServerless config server failed to start. Port already in use?")
		return nil
	}
}