users: Implement login key slot decoder

Issue #13

pkg/users/utils.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2022 Lukasz Janyst <lukasz@jany.st>
+//
+// This file is part of Peroxide.
+//
+// Peroxide is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Peroxide is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Peroxide.  If not, see <https://www.gnu.org/licenses/>.
+
+package users
+
+import (
+	"strings"
+)
+
+// Extract the login and key slot from the login information
+func DecodeLogin(login string) (string, string) {
+	if login == "" {
+		return "", "main"
+	}
+
+	splitLogin := strings.Split(login, "@")
+	if len(splitLogin) > 2 || len(splitLogin) == 0 {
+		return login, "main"
+	}
+
+	splitUser := strings.Split(splitLogin[0], "..")
+	if len(splitUser) > 2 || len(splitUser) == 0 {
+		return login, "main"
+	}
+
+	userName := splitUser[0]
+	slot := "main"
+	if len(splitUser) == 2 {
+		slot = splitUser[1]
+	}
+
+	if len(splitLogin) == 2 {
+		userName = userName + "@" + splitLogin[1]
+	}
+
+	return userName, slot
+}