[Core] add PsrLogger and support RFC 5424 log level

app/Mage.php

@@ -870,7 +870,7 @@ public static function isInstalled($options = [])
      * log facility (??)
      *
      * @param array|object|string $message
-     * @param null|int|Level::* $level
+     * @param null|int|Level::*|string $level
      * @param null|string $file
      * @param bool $forceLog
      */
@@ -906,8 +906,31 @@ public static function log($message, $level = null, $file = '', $forceLog = fals
             $levelValue = $level->value;
         } elseif (is_null($level)) {
             $levelValue = Level::Debug->value;
+        } elseif (is_string($level) && !is_numeric($level)) {
+            // PSR 3 Log level
+            try {
+                $levelValue = Level::fromName($level)->value;
+            } catch (ValueError) {
+                $levelValue = Level::Debug->value; // fallback to debug level
+            }
         } else {
             $levelValue = (int) $level;
+            // change RFC 5424 Log Level into Monolog.
+            if ($levelValue >= 0 && $levelValue <= 7) {
+                $levelValue = (match ($levelValue) {
+                    7 => Level::Debug,
+                    6 => Level::Info,
+                    5 => Level::Notice,
+                    4 => Level::Warning,
+                    3 => Level::Error,
+                    2 => Level::Critical,
+                    1 => Level::Alert,
+                    0 => Level::Emergency,
+                })->value;
+            } elseif ($levelValue < 100) {
+                // unknown levels are treated as debug
+                $levelValue = Level::Debug->value; // fallback to debug level
+            }
         }
 
         if (!self::$_isDeveloperMode && $levelValue > $maxLogLevel && !$forceLog) {

app/code/core/Mage/Core/Helper/PsrLogger.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @copyright  For copyright and license information, read the COPYING.txt file.
+ * @link       /COPYING.txt
+ * @license    Open Software License (OSL 3.0)
+ * @package    Mage_Core
+ */
+
+use Psr\Log\InvalidArgumentException;
+use Psr\Log\LoggerInterface;
+use Psr\Log\LoggerTrait;
+use Psr\Log\LogLevel;
+
+/**
+ * Provides a PSR-3 LoggerInterface implementation that wraps Mage::log().
+ *
+ * This class enables integration with PSR-3 compatible logging libraries and tools
+ * by forwarding log messages to the native Mage::log() method. It allows Magento
+ * modules and external libraries to use standardized logging practices within the
+ * OpenMage framework.
+ *
+ * @package    Mage_Core
+ */
+class Mage_Core_Helper_PsrLogger extends Mage_Core_Helper_Abstract implements LoggerInterface
+{
+    use LoggerTrait;
+
+    public function log($level, string|\Stringable $message, array $context = []): void
+    {
+        // unknown log level need to throw an InvalidArgumentException
+        $reflectionClass = new ReflectionClass(LogLevel::class);
+        if (!in_array($level, $reflectionClass->getConstants())) {
+            throw new InvalidArgumentException('Level "' . $level . '" is not defined, use one of: ' . implode(', ', $reflectionClass->getConstants()));
+        }
+
+        Mage::log((string) $message, $level, null, false, $context);
+    }
+}