feat(classifier): count_placeholder_fields() helper for drop-logic

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

includes/class-classifier.php

@@ -46,6 +46,14 @@ final class Classifier
         'rambler.ru', 'gmail.com',
     ];
 
+    /** Service field keys excluded from placeholder count. */
+    private const SERVICE_FIELD_KEYS = [
+        'acceptance-data',
+        '_wpcf7', '_wpcf7_version', '_wpcf7_locale', '_wpcf7_unit_tag',
+        '_wpcf7_container_post', '_wpcf7_posted_data_hash',
+        'g-recaptcha-response',
+    ];
+
     /**
      * @param array<string,mixed> $fields CF7 posted_data (field => value or array of values)
      * @param array{reason?:string} $meta  Context: reason = Akismet / Honeypot / CF7 rules / Неизвестно
@@ -266,4 +274,32 @@ final class Classifier
         if ($name === '') return false;
         return (bool)preg_match('/^[A-Za-z0-9]{1,3}$/', $name);
     }
+
+    /**
+     * Counts non-empty fields whose value is exactly 1-2 ASCII alphanumeric chars
+     * (the typical "AB", "70" placeholder pattern bots fill custom-keyed fields with).
+     *
+     * Skips service keys (acceptance-data, _wpcf7*, g-recaptcha-response) and any key
+     * starting with `_wpcf7`. Array values are joined without separators before length
+     * check (so `['A','B']` collapses to "AB" — still counted).
+     *
+     * @param array<string,string|string[]|null> $fields CF7 posted_data
+     * @return int Number of fields matching the placeholder pattern
+     */
+    public static function count_placeholder_fields(array $fields): int
+    {
+        $count = 0;
+        foreach ($fields as $k => $v) {
+            if (is_string($k)) {
+                if (in_array($k, self::SERVICE_FIELD_KEYS, true)) continue;
+                if (strpos($k, '_wpcf7') === 0) continue;
+            }
+            if (is_array($v)) $v = implode('', array_map('strval', $v));
+            $v = trim((string)$v);
+            if ($v === '') continue;
+            if (!preg_match('/^[A-Za-z0-9]{1,2}$/', $v)) continue;
+            $count++;
+        }
+        return $count;
+    }
 }