addr.go

package flagtypes

import (
	"fmt"
	"net"
	"net/url"
	"strconv"
	"strings"
)

// urlPrefixes is the list of string prefix values that may indicate a URL
// is present.
var urlPrefixes = []string{"http://", "https://", "tcp://", "unix://"}

// Addr is a flag type that attempts to load a host, IP, host:port, or
// URL value from a string argument. It tracks whether the value was set
// and allows the caller to provide defaults for the scheme and port.
type Addr struct {
	// Specified by the caller
	DefaultScheme string
	DefaultPort   int
	AllowPrefix   bool

	// Provided will be true if Set is invoked
	Provided bool
	// Value is the exact value provided on the flag
	Value string

	// URL represents the user input. The Host field is guaranteed
	// to be set if Provided is true
	URL *url.URL
	// Host is the hostname or IP portion of the user input
	Host string
	// IPv6Host is true if the hostname appears to be an IPv6 input
	IPv6Host bool
	// Port is the port portion of the user input. Will be 0 if no port was found
	// and no default port could be established.
	Port int
}

// Default creates a new Address with the value set
func (a Addr) Default() Addr {
	if err := a.Set(a.Value); err != nil {
		panic(err)
	}
	a.Provided = false
	return a
}

// String returns the string representation of the Addr
func (a *Addr) String() string {
	if a.URL == nil {
		return a.Value
	}
	return a.URL.String()
}

// Set attempts to set a string value to an address
func (a *Addr) Set(value string) error {
	scheme := a.DefaultScheme
	if len(scheme) == 0 {
		scheme = "tcp"
	}
	addr := &url.URL{
		Scheme: scheme,
	}

	switch {
	case a.isURL(value):
		parsed, err := url.Parse(value)
		if err != nil {
			return fmt.Errorf("not a valid URL: %v", err)
		}
		if !a.AllowPrefix {
			parsed.Path = ""
		}
		parsed.RawQuery = ""
		parsed.Fragment = ""

		if parsed.Scheme != "unix" && strings.Contains(parsed.Host, ":") {
			host, port, err := net.SplitHostPort(parsed.Host)
			if err != nil {
				return fmt.Errorf("not a valid host:port: %v", err)
			}
			portNum, err := strconv.ParseUint(port, 10, 64)
			if err != nil {
				return fmt.Errorf("not a valid port: %v", err)
			}
			a.Host = host
			a.Port = int(portNum)

		} else {
			port := 0
			switch parsed.Scheme {
			case "http":
				port = 80
			case "https":
				port = 443
			case "unix":
				port = 0
			default:
				return fmt.Errorf("no port specified")
			}
			a.Host = parsed.Host
			a.Port = port
		}
		addr = parsed

	case isIPv6Host(value):
		a.Host = value
		a.Port = a.DefaultPort

	case strings.Contains(value, ":"):
		host, port, err := net.SplitHostPort(value)
		if err != nil {
			return fmt.Errorf("not a valid host:port: %v", err)
		}
		portNum, err := strconv.ParseUint(port, 10, 64)
		if err != nil {
			return fmt.Errorf("not a valid port: %v", err)
		}
		a.Host = host
		a.Port = int(portNum)

	default:
		port := a.DefaultPort
		if port == 0 {
			switch a.DefaultScheme {
			case "http":
				port = 80
			case "https":
				port = 443
			default:
				return fmt.Errorf("no port specified")
			}
		}
		a.Host = value
		a.Port = port
	}
	if a.Port > 0 {
		addr.Host = net.JoinHostPort(a.Host, strconv.FormatInt(int64(a.Port), 10))
	} else {
		addr.Host = a.Host
	}

	if value != a.Value {
		a.Provided = true
	}
	a.URL = addr
	a.IPv6Host = isIPv6Host(a.Host)
	a.Value = value

	return nil
}

// Type returns a string representation of what kind of value this is
func (a *Addr) Type() string {
	return "string"
}

// isURL returns true if the provided value appears to be a valid URL.
func (a *Addr) isURL(value string) bool {
	prefixes := urlPrefixes
	if a.DefaultScheme != "" {
		prefixes = append(prefixes, fmt.Sprintf("%s://", a.DefaultScheme))
	}
	for _, p := range prefixes {
		if strings.HasPrefix(value, p) {
			return true
		}
	}
	return false
}

// isIPv6Host returns true if the value appears to be an IPv6 host string (that does
// not include a port).
func isIPv6Host(value string) bool {
	if strings.HasPrefix(value, "[") {
		return false
	}
	return strings.Contains(value, "%") || strings.Count(value, ":") > 1
}