Parse a command's vpn address operand in one place again

The move to Results dropped the helper master had for the first operand,
and six commands grew the same two refusals, four of them the same tunnel
lookup after it. One helper parses the operand and one looks the tunnel
up; the wording each command uses is kept, since the output golden pins it.

- vpnAddrOperand returns the address or the refusal to return
- tunnelOperand adds the hostmap lookup for close-tunnel, change-remote, print-cert and print-tunnel
- the IsValid check after a successful ParseAddr goes: a parsed address is valid

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

commands.go

@@ -336,14 +336,42 @@ func textVersion(vi versionInfo, w io.Writer) error {
 	return err
 }
 
-func runQueryLighthouse(ifce *Interface, a []string) (commands.Result, error) {
+// vpnAddrOperand parses the vpn address a command takes as its first operand. noun is
+// how the command's messages name it, "vpn address" or "vpn addr", which the output
+// golden pins per command. With no operand, or one that does not parse, ok is false and
+// res is the refusal to return.
+func vpnAddrOperand(a []string, noun string) (vpnAddr netip.Addr, res commands.Result, ok bool) {
 	if len(a) == 0 {
-		return commands.Failed("No vpn address was provided"), nil
+		return netip.Addr{}, commands.Failed("No vpn address was provided"), false
 	}
 
 	vpnAddr, err := netip.ParseAddr(a[0])
-	if err != nil || !vpnAddr.IsValid() {
-		return commands.Failed("The provided vpn address could not be parsed: %s", a[0]), nil
+	if err != nil {
+		return netip.Addr{}, commands.Failed("The provided %s could not be parsed: %s", noun, a[0]), false
+	}
+
+	return vpnAddr, commands.Result{}, true
+}
+
+// tunnelOperand is vpnAddrOperand followed by the lookup of the tunnel it names.
+func tunnelOperand(ifce *Interface, a []string, noun string) (*HostInfo, commands.Result, bool) {
+	vpnAddr, res, ok := vpnAddrOperand(a, noun)
+	if !ok {
+		return nil, res, false
+	}
+
+	hostInfo := ifce.hostMap.QueryVpnAddr(vpnAddr)
+	if hostInfo == nil {
+		return nil, commands.Failed("Could not find tunnel for %s: %v", noun, a[0]), false
+	}
+
+	return hostInfo, commands.Result{}, true
+}
+
+func runQueryLighthouse(ifce *Interface, a []string) (commands.Result, error) {
+	vpnAddr, res, ok := vpnAddrOperand(a, "vpn address")
+	if !ok {
+		return res, nil
 	}
 
 	var cm *CacheMap
@@ -355,19 +383,9 @@ func runQueryLighthouse(ifce *Interface, a []string) (commands.Result, error) {
 }
 
 func runCloseTunnel(ifce *Interface, flags *closeTunnelFlags, a []string) (commands.Result, error) {
-
-	if len(a) == 0 {
-		return commands.Failed("No vpn address was provided"), nil
-	}
-
-	vpnAddr, err := netip.ParseAddr(a[0])
-	if err != nil || !vpnAddr.IsValid() {
-		return commands.Failed("The provided vpn address could not be parsed: %s", a[0]), nil
-	}
-
-	hostInfo := ifce.hostMap.QueryVpnAddr(vpnAddr)
-	if hostInfo == nil {
-		return commands.Failed("Could not find tunnel for vpn address: %v", a[0]), nil
+	hostInfo, res, ok := tunnelOperand(ifce, a, "vpn address")
+	if !ok {
+		return res, nil
 	}
 
 	if !flags.LocalOnly {
@@ -388,13 +406,9 @@ func runCloseTunnel(ifce *Interface, flags *closeTunnelFlags, a []string) (comma
 
 func runCreateTunnel(ifce *Interface, flags *createTunnelFlags, a []string) (commands.Result, error) {
 
-	if len(a) == 0 {
-		return commands.Failed("No vpn address was provided"), nil
-	}
-
-	vpnAddr, err := netip.ParseAddr(a[0])
-	if err != nil || !vpnAddr.IsValid() {
-		return commands.Failed("The provided vpn address could not be parsed: %s", a[0]), nil
+	vpnAddr, res, ok := vpnAddrOperand(a, "vpn address")
+	if !ok {
+		return res, nil
 	}
 
 	if hostInfo := ifce.hostMap.QueryVpnAddr(vpnAddr); hostInfo != nil {
@@ -407,6 +421,7 @@ func runCreateTunnel(ifce *Interface, flags *createTunnelFlags, a []string) (com
 
 	var addr netip.AddrPort
 	if flags.Address != "" {
+		var err error
 		addr, err = netip.ParseAddrPort(flags.Address)
 		if err != nil {
 			return commands.Failed("Address could not be parsed"), nil
@@ -440,14 +455,9 @@ func runChangeRemote(ifce *Interface, flags *changeRemoteFlags, a []string) (com
 		return commands.Failed("Address could not be parsed"), nil
 	}
 
-	vpnAddr, err := netip.ParseAddr(a[0])
-	if err != nil || !vpnAddr.IsValid() {
-		return commands.Failed("The provided vpn address could not be parsed: %s", a[0]), nil
-	}
-
-	hostInfo := ifce.hostMap.QueryVpnAddr(vpnAddr)
-	if hostInfo == nil {
-		return commands.Failed("Could not find tunnel for vpn address: %v", a[0]), nil
+	hostInfo, res, ok := tunnelOperand(ifce, a, "vpn address")
+	if !ok {
+		return res, nil
 	}
 
 	hostInfo.SetRemote(addr)
@@ -507,16 +517,10 @@ func runPrintCert(ifce *Interface, args *printCertFlags, a []string) (commands.R
 
 	c := ifce.pki.getCertState().GetDefaultCertificate()
 	if len(a) > 0 {
-		vpnAddr, err := netip.ParseAddr(a[0])
-		if err != nil || !vpnAddr.IsValid() {
-			return commands.Failed("The provided vpn addr could not be parsed: %s", a[0]), nil
+		hostInfo, res, ok := tunnelOperand(ifce, a, "vpn addr")
+		if !ok {
+			return res, nil
 		}
-
-		hostInfo := ifce.hostMap.QueryVpnAddr(vpnAddr)
-		if hostInfo == nil {
-			return commands.Failed("Could not find tunnel for vpn addr: %v", a[0]), nil
-		}
-
 		c = hostInfo.GetCert().Certificate
 	}
 
@@ -607,18 +611,9 @@ func runPrintRelays(ifce *Interface) any {
 }
 
 func runPrintTunnel(ifce *Interface, a []string) (commands.Result, error) {
-	if len(a) == 0 {
-		return commands.Failed("No vpn address was provided"), nil
-	}
-
-	vpnAddr, err := netip.ParseAddr(a[0])
-	if err != nil || !vpnAddr.IsValid() {
-		return commands.Failed("The provided vpn addr could not be parsed: %s", a[0]), nil
-	}
-
-	hostInfo := ifce.hostMap.QueryVpnAddr(vpnAddr)
-	if hostInfo == nil {
-		return commands.Failed("Could not find tunnel for vpn addr: %v", a[0]), nil
+	hostInfo, res, ok := tunnelOperand(ifce, a, "vpn addr")
+	if !ok {
+		return res, nil
 	}
 
 	return commands.Value(copyHostInfo(hostInfo, ifce.hostMap.GetPreferredRanges())), nil