url.go

package url

import (
	"errors"
	"net"
	"net/url"
	"strings"
)

func AddPortToURL(hostUrl, port string) (*url.URL, error) {
	if !strings.HasPrefix(hostUrl, "http") {
		return nil, errors.New("No scheme provided for host URL")
	}
	url, err := url.Parse(hostUrl)
	if err != nil {
		return nil, err
	}

	// strip : from port if it exists
	port = strings.Replace(port, ":", "", strings.Count(port, ":"))

	host := url.Host

	// split apart host and port, if any port exists already
	// then build back up with the port passed in to this function
	host, p, err := net.SplitHostPort(url.Host)
	if err != nil {
		addErr := err.(*net.AddrError)
		if addErr.Err == "missing port in address" {
			host = url.Host
		} else {
			return err
		}
	}

	if port == "" {
		url.Host = host
	} else if strings.HasPrefix(url.Host, "[") {
		// JoinHostPort does not already handle existing [ and ]
		// it will just add more [ and ] to host e.g. [[host]]
		url.Host = host + ":" + port
	} else {
		url.Host = net.JoinHostPort(host, port)
	}

	return url, nil
}