<?php
// Logs recognized AI/search crawler user-agents that request public static evidence files, then serves the file unchanged.
$root=__DIR__; $dir=$root.'/private-data'; if(!is_dir($dir)) @mkdir($dir,0750,true);
$requested=trim($_GET['path'] ?? 'index.html','/');
if($requested==='' ) $requested='index.html';
if(strpos($requested,'..')!==false || strpos($requested,"\0")!==false) { http_response_code(400); exit; }
$target=realpath($root.'/'.$requested); $rootReal=realpath($root);
if(!$target || strpos($target,$rootReal)!==0 || !is_file($target)) { http_response_code(404); exit; }
$ua=$_SERVER['HTTP_USER_AGENT']??'';
$bots=['OAI-SearchBot'=>'OpenAI Search','GPTBot'=>'OpenAI Training','ChatGPT-User'=>'OpenAI User Fetch','Claude-SearchBot'=>'Anthropic Search','Claude-User'=>'Anthropic User Fetch','ClaudeBot'=>'Anthropic Training','PerplexityBot'=>'Perplexity Search','Perplexity-User'=>'Perplexity User Fetch','Google-Extended'=>'Google AI Control','Googlebot'=>'Google Search','Applebot-Extended'=>'Apple AI','Applebot'=>'Apple Search','CCBot'=>'Common Crawl','Amazonbot'=>'Amazon','Bytespider'=>'ByteDance','meta-externalagent'=>'Meta External Agent','Meta-ExternalAgent'=>'Meta External Agent','cohere-ai'=>'Cohere'];
$label='Recognized automated client'; foreach($bots as $needle=>$name){ if(stripos($ua,$needle)!==false){$label=$name;break;} }
$saltFile=$dir.'/.ai-log-salt'; if(!file_exists($saltFile)) @file_put_contents($saltFile,bin2hex(random_bytes(24)),LOCK_EX); $salt=@file_get_contents($saltFile)?:'useworthy';
$row=['ts'=>gmdate('c'),'channel'=>'crawler','bot'=>$label,'method'=>$_SERVER['REQUEST_METHOD']??'GET','path'=>'/'.$requested,'user_agent'=>$ua,'ip_hash'=>hash('sha256',$salt.'|'.($_SERVER['REMOTE_ADDR']??'')),'referer'=>substr($_SERVER['HTTP_REFERER']??'',0,500)];
$log=$dir.'/ai-crawler.ndjson'; if(file_exists($log)&&filesize($log)>10485760) @rename($log,$log.'.1'); @file_put_contents($log,json_encode($row,JSON_UNESCAPED_SLASHES|JSON_UNESCAPED_UNICODE)."\n",FILE_APPEND|LOCK_EX);
$ext=strtolower(pathinfo($target,PATHINFO_EXTENSION)); $types=['html'=>'text/html; charset=utf-8','md'=>'text/markdown; charset=utf-8','txt'=>'text/plain; charset=utf-8','json'=>'application/json; charset=utf-8','xml'=>'application/xml; charset=utf-8'];
header('Content-Type: '.($types[$ext]??'application/octet-stream')); header('X-Useworthy-Crawler-Logged: 1'); header('Vary: User-Agent');
$mtime=filemtime($target); $etag='"'.sha1_file($target).'"'; header('ETag: '.$etag); header('Last-Modified: '.gmdate('D, d M Y H:i:s',$mtime).' GMT');
if(($_SERVER['HTTP_IF_NONE_MATCH']??'')===$etag){http_response_code(304);exit;}
if($ext==='html'){
  $md=preg_replace('/\.html$/','.md','/'.$requested); if($requested==='index.html')$md='/index.md';
  header('Link: <'.$md.'>; rel="alternate"; type="text/markdown", </llms.txt>; rel="describedby"');
}
readfile($target);
?>