Add subscribe URL retrieval to server poll

src/classes/Pollers/Server.php

@@ -147,6 +147,10 @@ class Server
 				$addons = $probe_result['data']['plugins'];
 			}
 
+			if ($probe_result['data']['admin']['profile']) {
+				$subscribe = $this->getSubscribeUrl($probe_result['data']['url'], $probe_result['data']['admin']['profile']);
+			}
+
 			$this->atlas->perform(
 				'UPDATE `server`
 				SET `available`     = 1,
@@ -161,6 +165,7 @@ class Server
 					`admin_name`    = :admin_name,
 					`admin_profile` = :admin_profile,
 					`noscrape_url`  = :noscrape_url,
+					`subscribe_url` = :subscribe_url,
 					`ssl_state`     = :ssl_state
 				WHERE `id` = :server_id',
 				[
@@ -175,6 +180,7 @@ class Server
 					'admin_name'    => $probe_result['data']['admin']['name'],
 					'admin_profile' => $probe_result['data']['admin']['profile'],
 					'noscrape_url'  => $probe_result['data']['no_scrape_url'] ?? null,
+					'subscribe_url' => $subscribe ?? null,
 					'ssl_state'     => $probe_result['ssl_state']
 				]
 			);
@@ -452,4 +458,38 @@ class Server
 			}
 		}
 	}
+
+	public function getSubscribeUrl($base_url, $profile)
+	{
+		$xrdRequest = new WebRequest($base_url . '/xrd');
+		$xrdRequest->addRequestHeader('Accept', 'application/jrd+json');
+		$xrdJsonData = $xrdRequest->get(['uri' => $profile]);
+
+		$this->logger->debug('WebRequest: ' . $xrdRequest->getLastFetchedUrl() . ' Status: ' . $xrdRequest->getLastStatus());
+
+		if ($xrdRequest->getLastStatus() != 200) {
+			$this->logger->info('Unsuccessful XRD request: ' . $xrdRequest->getLastFetchedUrl());
+			return null;
+		}
+
+		try {
+			$xrdData = json_decode($xrdJsonData);
+		} catch (\Throwable $e) {
+			$this->logger->notice('Invalid JSON string for XRD URL: ' . $xrdRequest->getLastFetchedUrl());
+			return null;
+		}
+
+		if (!isset($xrdData->links)) {
+			$this->logger->notice('Invalid JSON structure for XRD URL: ' . $xrdRequest->getLastFetchedUrl());
+			return null;
+		}
+
+		foreach ($xrdData->links as $link) {
+			if ($link->rel == 'http://ostatus.org/schema/1.0/subscribe') {
+				return $link->template ?? null;
+			}
+		}
+
+		return null;
+	}
 }