Refactor saving session and system data to prevent saving older saves on previous waves (#26)

* chore: Refactor saving session data to prevent saving older sessions

* chore: Refactor saving system data to prevent saving older sessions

* Refactor saving session and system data to prevent saving older versions

db/savedata.go

@@ -20,6 +20,7 @@ package db
 import (
 	"bytes"
 	"encoding/gob"
+	"errors"
 
 	"github.com/pagefaultgames/rogueserver/defs"
 )
@@ -69,8 +70,13 @@ func ReadSystemSaveData(uuid []byte) (defs.SystemSaveData, error) {
 }
 
 func StoreSystemSaveData(uuid []byte, data defs.SystemSaveData) error {
+	systemData, err := ReadSystemSaveData(uuid)
+	if err == nil && systemData.Timestamp > data.Timestamp {
+		return errors.New("attempted to save an older system save")
+	}
+
 	var buf bytes.Buffer
-	err := gob.NewEncoder(&buf).Encode(data)
+	err = gob.NewEncoder(&buf).Encode(data)
 	if err != nil {
 		return err
 	}
@@ -120,8 +126,13 @@ func GetLatestSessionSaveDataSlot(uuid []byte) (int, error) {
 }
 
 func StoreSessionSaveData(uuid []byte, data defs.SessionSaveData, slot int) error {
+	session, err := ReadSessionSaveData(uuid, slot)
+	if err == nil && session.Seed == data.Seed && session.WaveIndex > data.WaveIndex {
+		return errors.New("attempted to save an older session")
+	}
+
 	var buf bytes.Buffer
-	err := gob.NewEncoder(&buf).Encode(data)
+	err = gob.NewEncoder(&buf).Encode(data)
 	if err != nil {
 		return err
 	}