fix error when there is no history file yet

.gitignore

@@ -15,5 +15,8 @@
 /hack/switch/switcher_darwin_amd64
 /hack/switch/switcher_darwin_amd64.tar.gz
 
+/hack/switch/switcher_darwin_arm64
+/hack/switch/switcher_darwin_arm64.tar.gz
+
 /hack/switch/switcher_linux_amd64
 /hack/switch/switcher_linux_amd64.tar.gz

pkg/subcommands/history/history.go

@@ -34,6 +34,8 @@ func SwitchToHistory(stores []store.KubeconfigStore, config *types.Config, state
 		return err
 	}
 
+	historyLength := len(history)
+
 	idx, err := fuzzyfinder.Find(
 		history,
 		func(i int) string {
@@ -48,6 +50,10 @@ func SwitchToHistory(stores []store.KubeconfigStore, config *types.Config, state
 				return fmt.Sprintf("%d: %s", len(history)-i-1, *context)
 			}
 
+			if i+1 == historyLength {
+				return fmt.Sprintf("%d: %s (ns: %s)", 0, *context, *ns)
+			}
+
 			previousContext, _, err := util.ParseHistoryEntry(history[i+1])
 			if err != nil {
 				logger.Debugf("failed to parse previous namespace history entry")

pkg/subcommands/history/util/util.go

@@ -30,6 +30,9 @@ func ReadHistory() ([]string, error) {
 	fileName := os.ExpandEnv(historyFilePath)
 	file, err := os.Open(fileName)
 	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, fmt.Errorf("no history entries yet - please run `switch` first")
+		}
 		return nil, err
 	}
 	defer file.Close()
@@ -46,6 +49,13 @@ func ReadHistory() ([]string, error) {
 // AppendToHistory appends the given context: namespace to the history file
 func AppendToHistory(context, namespace string) error {
 	filepath := os.ExpandEnv(historyFilePath)
+	f, err := os.OpenFile(filepath,
+		os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
 	historyEntry := fmt.Sprintf("%s:: %s\n", context, namespace)
 
 	lastHistoryEntry, err := getLastLineWithSeek(filepath)
@@ -54,17 +64,10 @@ func AppendToHistory(context, namespace string) error {
 	}
 
 	// do not entry history entry if previous entry is identical
-	if strings.Contains(historyEntry, lastHistoryEntry) {
+	if historyEntry == lastHistoryEntry {
 		return nil
 	}
 
-	f, err := os.OpenFile(filepath,
-		os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
 	if _, err := f.WriteString(historyEntry); err != nil {
 		return err
 	}
@@ -99,6 +102,11 @@ func getLastLineWithSeek(filepath string) (string, error) {
 	var cursor int64 = 0
 	stat, _ := fileHandle.Stat()
 	filesize := stat.Size()
+
+	if filesize == 0 {
+		return "", nil
+	}
+
 	for {
 		cursor -= 1
 		if _, err := fileHandle.Seek(cursor, io.SeekEnd); err != nil {