/**
* Parses a robots.txt-file and returns regular-expression-rules corresponding to the containing "disallow"-rules
* that are adressed to the given user-agent.
*
* @param PHPCrawlerURLDescriptor $BaseUrl The root-URL all rules from the robots-txt-file should relate to
* @param string $user_agent_string The useragent all rules from the robots-txt-file should relate to
* @param string $robots_txt_uri Optional. The location of the robots.txt-file as URI.
* If not set, the default robots.txt-file for the given BaseUrl gets parsed.
*
* @return array Numeric array containing regular-expressions for each "disallow"-rule defined in the robots.txt-file
* that's adressed to the given user-agent.
*/
public function parseRobotsTxt(PHPCrawlerURLDescriptor $BaseUrl, $user_agent_string, $robots_txt_uri = null)
{
PHPCrawlerBenchmark::start("processing_robotstxt");
// If robots_txt_uri not given, use the default one for the given BaseUrl
if ($robots_txt_uri === null) {
$robots_txt_uri = self::getRobotsTxtURL($BaseUrl->url_rebuild);
}
// Get robots.txt-content
$robots_txt_content = PHPCrawlerUtils::getURIContent($robots_txt_uri, $user_agent_string);
$non_follow_reg_exps = array();
// If content was found
if ($robots_txt_content != null) {
// Get all lines in the robots.txt-content that are adressed to our user-agent.
$applying_lines = $this->getUserAgentLines($robots_txt_content, $user_agent_string);
// Get valid reg-expressions for the given disallow-pathes.
$non_follow_reg_exps = $this->buildRegExpressions($applying_lines, PHPCrawlerUtils::getRootUrl($BaseUrl->url_rebuild));
}
PHPCrawlerBenchmark::stop("processing_robots.txt");
return $non_follow_reg_exps;
}