feat: smtp sending

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

lib/Smtp/SmtpCapabilities.php

@@ -0,0 +1,72 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: Sebastian Krupinski <krupinski01@gmail.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace KTXM\ProviderImap\Smtp;
+
+use KTXM\ProviderImap\Smtp\Protocol\Reply;
+
+/**
+ * Parsed EHLO capabilities.
+ *
+ * The first line of an EHLO reply is the server greeting/domain; every
+ * subsequent line is a capability keyword optionally followed by parameters
+ * (e.g. "AUTH PLAIN LOGIN", "SIZE 35882577").
+ */
+final class SmtpCapabilities
+{
+    /**
+     * @param array<string,list<string>> $keywords capability keyword => parameters
+     */
+    private function __construct(
+        private readonly array $keywords,
+    ) {}
+
+    public static function fromEhlo(Reply $reply): self
+    {
+        $keywords = [];
+        $lines = $reply->lines();
+
+        // Skip the first line (greeting/domain); the rest are capabilities.
+        foreach (array_slice($lines, 1) as $line) {
+            $parts = preg_split('/\s+/', trim($line)) ?: [];
+            $keyword = strtoupper((string) array_shift($parts));
+            if ($keyword === '') {
+                continue;
+            }
+            $keywords[$keyword] = array_map('strtoupper', $parts);
+        }
+
+        return new self($keywords);
+    }
+
+    public function has(string $keyword): bool
+    {
+        return isset($this->keywords[strtoupper($keyword)]);
+    }
+
+    public function supportsStartTls(): bool
+    {
+        return $this->has('STARTTLS');
+    }
+
+    /**
+     * @return list<string> Advertised AUTH mechanisms (uppercased).
+     */
+    public function authMechanisms(): array
+    {
+        return $this->keywords['AUTH'] ?? [];
+    }
+
+    public function maxSize(): ?int
+    {
+        $size = $this->keywords['SIZE'][0] ?? null;
+
+        return $size !== null && ctype_digit($size) ? (int) $size : null;
+    }
+}