Maint: configuration Openvpn selection structure

- Move network protocol from ServerSelection to OpenVPNSelection child
- Move PIA encryption preset from ServerSelection to OpenVPNSelection child
- Move custom port from ServerSelection to OpenVPNSelection child

internal/configuration/selection.go

@@ -1,12 +1,14 @@
 package configuration
 
 import (
+	"fmt"
 	"net"
+
+	"github.com/qdm12/golibs/params"
 )
 
 type ServerSelection struct { //nolint:maligned
 	// Common
-	TCP      bool   `json:"tcp"` // UDP if TCP is false
 	TargetIP net.IP `json:"target_ip,omitempty"`
 	// TODO comments
 	// Cyberghost, PIA, Protonvpn, Surfshark, Windscribe, Vyprvpn, NordVPN
@@ -27,20 +29,57 @@ type ServerSelection struct { //nolint:maligned
 	ISPs  []string `json:"isps"`
 	Owned bool     `json:"owned"`
 
-	// Mullvad, Windscribe, PIA
-	CustomPort uint16 `json:"custom_port"`
-
 	// NordVPN
 	Numbers []uint16 `json:"numbers"`
 
-	// PIA - needed to get the port number
-	EncryptionPreset string `json:"encryption_preset"`
-
 	// ProtonVPN
 	FreeOnly bool `json:"free_only"`
 
 	// VPNUnlimited
 	StreamOnly bool `json:"stream_only"`
+
+	OpenVPN OpenVPNSelection `json:"openvpn"`
+}
+
+type OpenVPNSelection struct {
+	TCP        bool   `json:"tcp"`               // UDP if TCP is false
+	CustomPort uint16 `json:"custom_port"`       // HideMyAss, Mullvad, PIA, ProtonVPN, Windscribe
+	EncPreset  string `json:"encryption_preset"` // PIA - needed to get the port number
+}
+
+func (settings *OpenVPNSelection) lines() (lines []string) {
+	lines = append(lines, lastIndent+"OpenVPN selection:")
+
+	lines = append(lines, indent+lastIndent+"Protocol: "+protoToString(settings.TCP))
+
+	if settings.CustomPort != 0 {
+		lines = append(lines, indent+lastIndent+"Custom port: "+fmt.Sprint(settings.CustomPort))
+	}
+
+	if settings.EncPreset != "" {
+		lines = append(lines, indent+lastIndent+"PIA encryption preset: "+settings.EncPreset)
+	}
+
+	return lines
+}
+
+func (settings *OpenVPNSelection) readProtocolOnly(env params.Env) (err error) {
+	settings.TCP, err = readProtocol(env)
+	return err
+}
+
+func (settings *OpenVPNSelection) readProtocolAndPort(env params.Env) (err error) {
+	settings.TCP, err = readProtocol(env)
+	if err != nil {
+		return err
+	}
+
+	settings.CustomPort, err = readPortOrZero(env, "PORT")
+	if err != nil {
+		return fmt.Errorf("environment variable PORT: %w", err)
+	}
+
+	return nil
 }
 
 // PortForwarding contains settings for port forwarding.