Fix file processing and optimize when the same file if multiple times

src/PHPMailerEnhanced/PHPMailerEnhanced.php

@@ -209,7 +209,7 @@ class PHPMailerEnhanced extends PHPMailer {
                 $link = $match[0];
 
                 //region Check the link has no protocol (http, cid, etc.) or it's “file”
-                if (preg_match('#^(?<protocol>[a-z][a-z\d+.-]*):(?<path>.+)$#i', $link, $match) === 1) {
+                if (preg_match('#^(?:(?<protocol>[a-z][a-z\d+.-]*):)?(?<path>.+)$#i', $link, $match) === 1) {
                     if (($match['protocol'] ?? '') !== 'file') {
                         return $link;
                     }
@@ -229,11 +229,17 @@ class PHPMailerEnhanced extends PHPMailer {
                         return $link;
                     }
                 }
+                $path = realpath($path);
                 //endregion
 
                 //region Associate a cid to the file
-                $cid = $this->cidGenerate();
-                $embeddedImages[$cid] = $path;
+                if (array_key_exists($path, $embeddedImages)) {
+                    $cid = $embeddedImages[$path];
+                }
+                else {
+                    $cid = $this->cidGenerate();
+                    $embeddedImages[$path] = $cid;
+                }
                 //endregion
 
                 return 'cid:' . $cid;
@@ -251,7 +257,7 @@ class PHPMailerEnhanced extends PHPMailer {
         $this->$bodyProperty = $body;
         //endregion
         //region Embed the files in the mail
-        foreach ($embeddedImages as $cid => $path) {
+        foreach ($embeddedImages as $path => $cid) {
             $this->addEmbeddedImage($path, $cid);
         }
         //endregion