Feat: rework Surfshark servers data (#575)

- Feat: `MULTIHOP_ONLY` variable
- Feat: `COUNTRY` variable
- Feat: `CITY` variable
- Feat: `REGION` variable, with retro-compatibility
- Feat: merge servers from API, zip and hardcoded hostnames
- Fix: remove outdated and duplicate servers
- Maint: faster update with fully parallel DNS resolutions

internal/configuration/selection.go

@@ -40,6 +40,9 @@ type ServerSelection struct { //nolint:maligned
 	// VPNUnlimited
 	StreamOnly bool `json:"stream_only"`
 
+	// Surfshark
+	MultiHopOnly bool `json:"multihop_only"`
+
 	OpenVPN   OpenVPNSelection   `json:"openvpn"`
 	Wireguard WireguardSelection `json:"wireguard"`
 }

internal/configuration/surfshark.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
 )
 
 func (settings *Provider) readSurfshark(r reader) (err error) {
@@ -14,9 +15,14 @@ func (settings *Provider) readSurfshark(r reader) (err error) {
 		return err
 	}
 
-	settings.ServerSelection.Regions, err = r.env.CSVInside("REGION", constants.SurfsharkRegionChoices())
+	settings.ServerSelection.Countries, err = r.env.CSVInside("COUNTRY", constants.SurfsharkCountryChoices())
 	if err != nil {
-		return fmt.Errorf("environment variable REGION: %w", err)
+		return fmt.Errorf("environment variable COUNTRY: %w", err)
+	}
+
+	settings.ServerSelection.Cities, err = r.env.CSVInside("CITY", constants.SurfsharkCityChoices())
+	if err != nil {
+		return fmt.Errorf("environment variable CITY: %w", err)
 	}
 
 	settings.ServerSelection.Hostnames, err = r.env.CSVInside("SERVER_HOSTNAME", constants.SurfsharkHostnameChoices())
@@ -24,5 +30,45 @@ func (settings *Provider) readSurfshark(r reader) (err error) {
 		return fmt.Errorf("environment variable SERVER_HOSTNAME: %w", err)
 	}
 
+	regionChoices := constants.SurfsharkRegionChoices()
+	regionChoices = append(regionChoices, constants.SurfsharkRetroLocChoices()...)
+	regions, err := r.env.CSVInside("REGION", regionChoices)
+	if err != nil {
+		return fmt.Errorf("environment variable REGION: %w", err)
+	}
+
+	// Retro compatibility
+	// TODO remove in v4
+	for i, region := range regions {
+		locationData, isRetro :=
+			surfsharkConvertRetroLoc(region)
+		if !isRetro {
+			continue
+		}
+
+		regions[i] = locationData.Region
+		settings.ServerSelection.Countries = append(settings.ServerSelection.Countries, locationData.Country)
+		if locationData.City != "" { // city is empty for some servers
+			settings.ServerSelection.Cities = append(settings.ServerSelection.Cities, locationData.City)
+		}
+		settings.ServerSelection.Hostnames = append(settings.ServerSelection.Hostnames, locationData.Hostname)
+	}
+
+	settings.ServerSelection.MultiHopOnly, err = r.env.YesNo("MULTIHOP_ONLY")
+	if err != nil {
+		return fmt.Errorf("environment variable MULTIHOP_ONLY: %w", err)
+	}
+
 	return settings.ServerSelection.OpenVPN.readProtocolOnly(r.env)
 }
+
+// TODO remove in v4.
+func surfsharkConvertRetroLoc(retroLoc string) (
+	locationData models.SurfsharkLocationData, isRetro bool) {
+	for _, data := range constants.SurfsharkLocationData() {
+		if retroLoc == data.RetroLoc {
+			return data, true
+		}
+	}
+	return locationData, false
+}