Implement IMAP email-to-ticket gateway

InboundPolicy.php

@@ -0,0 +1,101 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Box\Mod\Mailgateway;
+
+use FOSSBilling\InformationException;
+
+class InboundPolicy
+{
+    private const FIELDS = [
+        'auto-submitted', 'precedence', 'return-path', 'content-type',
+        'x-auto-response-suppress', 'x-autoreply', 'x-autorespond', 'list-id',
+    ];
+
+    /** Normalize parsed MIME headers and supported flat header fields. */
+    public function headers(array $data): array
+    {
+        $raw = $data['headers'] ?? [];
+        if (!is_array($raw)) {
+            throw new InformationException('headers must be an array of header values');
+        }
+        foreach (self::FIELDS as $field) {
+            $flat = str_replace('-', '_', $field);
+            if (array_key_exists($flat, $data)) {
+                $raw[$field] = array_merge((array) ($raw[$field] ?? []), (array) $data[$flat]);
+            }
+        }
+        $headers = [];
+        foreach ($raw as $name => $values) {
+            if (!is_string($name)) {
+                throw new InformationException('Header names must be strings');
+            }
+            $name = strtolower(str_replace('_', '-', $name));
+            if (!in_array($name, self::FIELDS, true)) {
+                continue;
+            }
+            $values = is_array($values) ? $values : [$values];
+            if (count($values) > 20) {
+                throw new InformationException('Too many repeated header values');
+            }
+            foreach ($values as $value) {
+                if (!is_string($value) || strlen($value) > 16384) {
+                    throw new InformationException('Header values must be strings of at most 16384 bytes');
+                }
+                $value = preg_replace('/\r?\n[ \t]+/', ' ', $value);
+                if (preg_match('/[\x00-\x08\x0A-\x1F\x7F]/', $value)) {
+                    throw new InformationException('Invalid control character in header value');
+                }
+                $headers[$name][] = strtolower(trim($value));
+            }
+        }
+        ksort($headers);
+
+        return $headers;
+    }
+
+    public function ignoreReason(array $headers): ?string
+    {
+        foreach ($headers['auto-submitted'] ?? [] as $value) {
+            if (trim(explode(';', $value, 2)[0]) !== 'no') {
+                return 'auto_submitted';
+            }
+        }
+        foreach ($headers['return-path'] ?? [] as $value) {
+            if (preg_match('/^<\s*>$/D', $value)) {
+                return 'null_return_path';
+            }
+        }
+        foreach ($headers['content-type'] ?? [] as $value) {
+            if (preg_match('/^multipart\/report\s*(?:;|$)/', $value)
+                || preg_match('/^message\/(?:delivery-status|disposition-notification|global-delivery-status)\s*(?:;|$)/', $value)) {
+                return 'delivery_report';
+            }
+        }
+        foreach ($headers['precedence'] ?? [] as $value) {
+            if (in_array(trim(explode(';', $value, 2)[0]), ['bulk', 'list', 'junk'], true)) {
+                return 'bulk_mail';
+            }
+        }
+        foreach ($headers['list-id'] ?? [] as $value) {
+            if ($value !== '') {
+                return 'mailing_list';
+            }
+        }
+        foreach ($headers['x-auto-response-suppress'] ?? [] as $value) {
+            if (preg_match('/(?:^|[\s,;])(?:all|autoreply|oof|dr|ndr|rn|nrn)(?:$|[\s,;])/', $value)) {
+                return 'response_suppressed';
+            }
+        }
+        foreach (['x-autoreply', 'x-autorespond'] as $field) {
+            foreach ($headers[$field] ?? [] as $value) {
+                if (!in_array($value, ['', 'no', 'false', '0'], true)) {
+                    return 'legacy_autoresponder';
+                }
+            }
+        }
+
+        return null;
+    }
+}