chore(validation): uniformize server filters build

internal/configuration/settings/validation/servers.go

@@ -0,0 +1,111 @@
+package validation
+
+import (
+	"sort"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+func sortedInsert(ss []string, s string) []string {
+	i := sort.SearchStrings(ss, s)
+	ss = append(ss, "")
+	copy(ss[i+1:], ss[i:])
+	ss[i] = s
+	return ss
+}
+
+func ExtractCountries(servers []models.Server) (values []string) {
+	seen := make(map[string]struct{}, len(servers))
+	values = make([]string, 0, len(servers))
+	for _, server := range servers {
+		value := server.Country
+		_, alreadySeen := seen[value]
+		if alreadySeen {
+			continue
+		}
+		seen[value] = struct{}{}
+
+		values = sortedInsert(values, value)
+	}
+	return values
+}
+
+func ExtractRegions(servers []models.Server) (values []string) {
+	seen := make(map[string]struct{}, len(servers))
+	values = make([]string, 0, len(servers))
+	for _, server := range servers {
+		value := server.Region
+		_, alreadySeen := seen[value]
+		if alreadySeen {
+			continue
+		}
+		seen[value] = struct{}{}
+
+		values = sortedInsert(values, value)
+	}
+	return values
+}
+
+func ExtractCities(servers []models.Server) (values []string) {
+	seen := make(map[string]struct{}, len(servers))
+	values = make([]string, 0, len(servers))
+	for _, server := range servers {
+		value := server.City
+		_, alreadySeen := seen[value]
+		if alreadySeen {
+			continue
+		}
+		seen[value] = struct{}{}
+
+		values = sortedInsert(values, value)
+	}
+	return values
+}
+
+func ExtractISPs(servers []models.Server) (values []string) {
+	seen := make(map[string]struct{}, len(servers))
+	values = make([]string, 0, len(servers))
+	for _, server := range servers {
+		value := server.ISP
+		_, alreadySeen := seen[value]
+		if alreadySeen {
+			continue
+		}
+		seen[value] = struct{}{}
+
+		values = sortedInsert(values, value)
+	}
+	return values
+}
+
+func ExtractServerNames(servers []models.Server) (values []string) {
+	seen := make(map[string]struct{}, len(servers))
+	values = make([]string, 0, len(servers))
+	for _, server := range servers {
+		value := server.ServerName
+		_, alreadySeen := seen[value]
+		if alreadySeen {
+			continue
+		}
+		seen[value] = struct{}{}
+
+		values = sortedInsert(values, value)
+	}
+	return values
+}
+
+func ExtractHostnames(servers []models.Server) (values []string) {
+	seen := make(map[string]struct{}, len(servers))
+	values = make([]string, 0, len(servers))
+	for _, server := range servers {
+		value := server.Hostname
+		_, alreadySeen := seen[value]
+		if alreadySeen {
+			continue
+		}
+		seen[value] = struct{}{}
+
+		values = sortedInsert(values, value)
+	}
+	return values
+}