Maintenance: refactor servers updater code

- Require at least 80% of number of servers now to pass
- Each provider is in its own package with a common structure
- Unzip package with unzipper interface
- Openvpn package with extraction and download functions

internal/updater/providers/protonvpn/servers.go

@@ -0,0 +1,98 @@
+// Package protonvpn contains code to obtain the server information
+// for the ProtonVPN provider.
+package protonvpn
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+var ErrNotEnoughServers = errors.New("not enough servers found")
+
+func GetServers(ctx context.Context, client *http.Client, minServers int) (
+	servers []models.ProtonvpnServer, warnings []string, err error) {
+	data, err := fetchAPI(ctx, client)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	countryCodes := constants.CountryCodes()
+
+	var count int
+	for _, logicalServer := range data.LogicalServers {
+		count += len(logicalServer.Servers)
+	}
+
+	if count < minServers {
+		return nil, warnings, fmt.Errorf("%w: %d and expected at least %d",
+			ErrNotEnoughServers, count, minServers)
+	}
+
+	servers = make([]models.ProtonvpnServer, 0, count)
+	for _, logicalServer := range data.LogicalServers {
+		for _, physicalServer := range logicalServer.Servers {
+			server, warning, err := makeServer(
+				physicalServer, logicalServer, countryCodes)
+
+			if warning != "" {
+				warnings = append(warnings, warning)
+			}
+
+			if err != nil {
+				warnings = append(warnings, err.Error())
+				continue
+			}
+
+			servers = append(servers, server)
+		}
+	}
+
+	if len(servers) < minServers {
+		return nil, warnings, fmt.Errorf("%w: %d and expected at least %d",
+			ErrNotEnoughServers, len(servers), minServers)
+	}
+
+	sortServers(servers)
+
+	return servers, warnings, nil
+}
+
+var errServerStatusZero = errors.New("ignoring server with status 0")
+
+func makeServer(physical physicalServer, logical logicalServer,
+	countryCodes map[string]string) (server models.ProtonvpnServer,
+	warning string, err error) {
+	if physical.Status == 0 {
+		return server, "", fmt.Errorf("%w: %s",
+			errServerStatusZero, physical.Domain)
+	}
+
+	countryCode := logical.ExitCountry
+	country, warning := codeToCountry(countryCode, countryCodes)
+
+	server = models.ProtonvpnServer{
+		// Note: for multi-hop use the server name or hostname
+		// instead of the country
+		Country:  country,
+		Region:   getStringValue(logical.Region),
+		City:     getStringValue(logical.City),
+		Name:     logical.Name,
+		Hostname: physical.Domain,
+		EntryIP:  physical.EntryIP,
+		ExitIP:   physical.ExitIP,
+	}
+
+	return server, warning, nil
+}
+
+func getStringValue(ptr *string) string {
+	if ptr == nil {
+		return ""
+	}
+	return *ptr
+}