4 files changed, 32 insertions, 10 deletions
diff --git a/lib/Minz/Extension.php b/lib/Minz/Extension.php
index a35d7d8b6..a280676c1 100644
--- a/lib/Minz/Extension.php
+++ b/lib/Minz/Extension.php
@@ -155,7 +155,7 @@ abstract class Minz_Extension {
 			$file_name_url = urlencode("{$dir}/static/{$filename}");
 			$mtime = @filemtime("{$this->path}/static/{$filename}");
 		} else {
-			$username = Minz_Session::param('currentUser');
+			$username = Minz_User::name();
 			$path = USERS_PATH . "/{$username}/{$this->config_key}/{$this->getName()}/{$filename}";
 			$file_name_url = urlencode("{$username}/{$this->config_key}/{$this->getName()}/{$filename}");
 			$mtime = @filemtime($path);
@@ -343,7 +343,7 @@ abstract class Minz_Extension {
 	}
 
 	public function saveFile(string $filename, string $content) {
-		$username = Minz_Session::param('currentUser');
+		$username = Minz_User::name();
 		$path = USERS_PATH . "/{$username}/{$this->config_key}/{$this->getName()}";
 
 		if (!file_exists($path)) {
@@ -354,7 +354,7 @@ abstract class Minz_Extension {
 	}
 
 	public function removeFile(string $filename) {
-		$username = Minz_Session::param('currentUser');
+		$username = Minz_User::name();
 		$path = USERS_PATH . "/{$username}/{$this->config_key}/{$this->getName()}/{$filename}";
 
 		if (file_exists($path)) {
diff --git a/lib/Minz/Log.php b/lib/Minz/Log.php
index 43f3c9d6d..117f231ac 100644
--- a/lib/Minz/Log.php
+++ b/lib/Minz/Log.php
@@ -31,14 +31,9 @@ class Minz_Log {
 		}
 
 		if (! ($env === 'silent' || ($env === 'production' && ($level >= LOG_NOTICE)))) {
-			$username = Minz_Session::param('currentUser', '');
-			if ($username == '') {
-				$username = '_';
-			}
+			$username = Minz_User::name() ?? Minz_User::INTERNAL_USER;
 			if ($file_name == null) {
 				$file_name = join_path(USERS_PATH, $username, LOG_FILENAME);
-			} else {
-				$username = '_';
 			}
 
 			switch ($level) {
diff --git a/lib/Minz/ModelPdo.php b/lib/Minz/ModelPdo.php
index 3bcf87247..b8c1ad89b 100644
--- a/lib/Minz/ModelPdo.php
+++ b/lib/Minz/ModelPdo.php
@@ -103,7 +103,7 @@ class Minz_ModelPdo {
 	 */
 	public function __construct($currentUser = null, $currentPdo = null) {
 		if ($currentUser === null) {
-			$currentUser = Minz_Session::param('currentUser');
+			$currentUser = Minz_User::name();
 		}
 		if ($currentPdo !== null) {
 			$this->pdo = $currentPdo;
diff --git a/lib/Minz/User.php b/lib/Minz/User.php
new file mode 100644
index 000000000..252584e83
--- /dev/null
+++ b/lib/Minz/User.php
@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * The Minz_User class handles the user information.
+ */
+final class Minz_User {
+
+	public const INTERNAL_USER = '_';
+
+	public const CURRENT_USER = 'currentUser';
+
+	/**
+	 * @return string the name of the current user, or null if there is none
+	 */
+	public static function name(): ?string {
+		$currentUser = trim(Minz_Session::param(Minz_User::CURRENT_USER, ''));
+		return $currentUser === '' ? null : $currentUser;
+	}
+
+	/**
+	 * @param string $name the name of the new user. Set to empty string to clear the user.
+	 */
+	public static function change(string $name = ''): void {
+		$name = trim($name);
+		Minz_Session::_param(Minz_User::CURRENT_USER, $name === '' ? false : $name);
+	}
+}