feat(storage): add keep field for servers

internal/storage/merge.go

@@ -1,6 +1,7 @@
 package storage
 
 import (
+	"sort"
 	"time"
 
 	"github.com/qdm12/gluetun/internal/constants/providers"
@@ -26,18 +27,47 @@ func (s *Storage) mergeServers(hardcoded, persisted models.AllServers) models.Al
 
 func (s *Storage) mergeProviderServers(provider string,
 	hardcoded, persisted models.Servers) (merged models.Servers) {
-	if persisted.Timestamp <= hardcoded.Timestamp {
-		return hardcoded
+	if persisted.Timestamp > hardcoded.Timestamp {
+		diff := time.Unix(persisted.Timestamp, 0).Sub(time.Unix(hardcoded.Timestamp, 0))
+		if diff < 0 {
+			diff = -diff
+		}
+		diff = diff.Truncate(time.Second)
+		message := "Using " + provider + " servers from file which are " +
+			diff.String() + " more recent"
+		s.logger.Info(message)
+
+		return persisted
 	}
 
-	diff := time.Unix(persisted.Timestamp, 0).Sub(time.Unix(hardcoded.Timestamp, 0))
-	if diff < 0 {
-		diff = -diff
+	persistedServerKeyToServer := make(map[string]models.Server)
+	for _, persistedServer := range persisted.Servers {
+		if persistedServer.Keep {
+			persistedServerKeyToServer[persistedServer.Key()] = persistedServer
+		}
 	}
-	diff = diff.Truncate(time.Second)
-	message := "Using " + provider + " servers from file which are " +
-		diff.String() + " more recent"
-	s.logger.Info(message)
 
-	return persisted
+	merged = hardcoded // use all fields from hardcoded
+	merged.Servers = make([]models.Server, 0, len(hardcoded.Servers)+len(persistedServerKeyToServer))
+
+	for _, hardcodedServer := range hardcoded.Servers {
+		hardcodedServerKey := hardcodedServer.Key()
+		persistedServerToKeep, has := persistedServerKeyToServer[hardcodedServerKey]
+		if has {
+			// Drop hardcoded server and use persisted server matching the key.
+			merged.Servers = append(merged.Servers, persistedServerToKeep)
+			delete(persistedServerKeyToServer, hardcodedServerKey)
+		} else {
+			merged.Servers = append(merged.Servers, hardcodedServer)
+		}
+	}
+
+	// Add remaining persisted servers to keep
+	for _, persistedServer := range persistedServerKeyToServer {
+		merged.Servers = append(merged.Servers, persistedServer)
+	}
+
+	sort.Sort(models.SortableServers(merged.Servers))
+
+	return merged
 }