feat: implement exim autoresponder worker

exec/lib/MailboxDirectory.php

@@ -30,25 +30,64 @@ final class MailboxDirectory
         return $out;
     }
 
+    /** @return array{owner:string,domain:string,mailbox:string,email:string}|null */
+    public function resolveRecipient(string $email): ?array
+    {
+        $email = strtolower(trim($email));
+        if (!preg_match('/^([A-Za-z0-9._+-]+)@([A-Za-z0-9.-]+)$/', $email, $m)) {
+            return null;
+        }
+        $local = $m[1];
+        $domain = $m[2];
+        $owners = $this->domainOwners();
+        $owner = $owners[$domain] ?? null;
+        if ($owner === null) {
+            return null;
+        }
+        $passwd = $this->virtualRoot . '/' . $domain . '/passwd';
+        if (!is_file($passwd)) {
+            return null;
+        }
+        foreach (file($passwd, FILE_IGNORE_NEW_LINES) ?: [] as $line) {
+            $mailbox = strtolower(trim(strtok($line, ':') ?: ''));
+            if ($mailbox === $local) {
+                return ['owner' => $owner, 'domain' => $domain, 'mailbox' => $local, 'email' => $local . '@' . $domain];
+            }
+        }
+        return null;
+    }
+
     /** @return string[] */
     private function domainsForUser(string $username): array
+    {
+        $domains = [];
+        foreach ($this->domainOwners() as $domain => $owner) {
+            if ($owner === $username) {
+                $domains[] = $domain;
+            }
+        }
+        sort($domains);
+        return $domains;
+    }
+
+    /** @return array<string,string> */
+    private function domainOwners(): array
     {
         $path = $this->virtualRoot . '/domainowners';
         if (!is_file($path)) {
             return [];
         }
-        $domains = [];
+        $owners = [];
         foreach (file($path, FILE_IGNORE_NEW_LINES) ?: [] as $line) {
             if (!str_contains($line, ':')) {
                 continue;
             }
             [$domain, $owner] = array_map('trim', explode(':', $line, 2));
-            if ($owner !== $username || !preg_match('/^[A-Za-z0-9.-]+$/', $domain)) {
+            if (!preg_match('/^[A-Za-z0-9.-]+$/', $domain) || !preg_match('/^[A-Za-z0-9._-]+$/', $owner)) {
                 continue;
             }
-            $domains[] = strtolower($domain);
+            $owners[strtolower($domain)] = $owner;
         }
-        sort($domains);
-        return $domains;
+        return $owners;
     }
 }