add new endpoint to parse all rel values from a URL

Grabs rel values from both HTTP headers and link tags and merges them together, and resolves any relative values. Also returns the final URL requested and the HTTP response.

composer.json

@@ -14,6 +14,7 @@
       "controllers/Main.php",
       "controllers/Parse.php",
       "controllers/Token.php",
+      "controllers/Rels.php",
       "controllers/Certbot.php",
       "lib/HTTPCurl.php",
       "lib/HTTPStream.php",

controllers/Rels.php

@@ -0,0 +1,93 @@
+<?php
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+
+class Rels {
+
+  public $http;
+  private $_pretty = false;
+
+  public function __construct() {
+    $this->http = new p3k\HTTP();
+  }
+
+  private function respond(Response $response, $code, $params, $headers=[]) {
+    $response->setStatusCode($code);
+    foreach($headers as $k=>$v) {
+      $response->headers->set($k, $v);
+    }
+    $response->headers->set('Content-Type', 'application/json');
+    $opts = JSON_UNESCAPED_SLASHES + JSON_FORCE_OBJECT;
+    if($this->_pretty) $opts += JSON_PRETTY_PRINT;
+    $response->setContent(json_encode($params, $opts)."\n");
+    return $response;
+  }
+
+  public function fetch(Request $request, Response $response) {
+    if($request->get('timeout')) {
+      // We might make 2 HTTP requests, so each request gets half the desired timeout
+      $this->http->timeout = $request->get('timeout') / 2;
+    }
+
+    if($request->get('max_redirects')) {
+      $this->http->max_redirects = (int)$request->get('max_redirects');
+    }
+
+    if($request->get('pretty')) {
+      $this->_pretty = true;
+    }
+
+    $url = $request->get('url');
+
+    if(!$url) {
+      return $this->respond($response, 400, [
+        'error' => 'missing_url',
+        'error_description' => 'Provide a URL to fetch'
+      ]);
+    }
+
+    // Attempt some basic URL validation
+    $scheme = parse_url($url, PHP_URL_SCHEME);
+    if(!in_array($scheme, ['http','https'])) {
+      return $this->respond($response, 400, [
+        'error' => 'invalid_url',
+        'error_description' => 'Only http and https URLs are supported'
+      ]);
+    }
+
+    $host = parse_url($url, PHP_URL_HOST);
+    if(!$host) {
+      return $this->respond($response, 400, [
+        'error' => 'invalid_url',
+        'error_description' => 'The URL provided was not valid'
+      ]);
+    }
+
+    $url = \normalize_url($url);
+
+    $result = $this->http->get($url);
+
+    $html = $result['body'];
+    $mf2 = mf2\Parse($html, $result['url']);
+
+    $rels = p3k\HTTP::link_rels($result['headers']);
+    if(isset($mf2['rels'])) {
+      $rels = array_merge($rels, $mf2['rels']);
+    }
+
+    // Resolve all relative URLs
+    foreach($rels as $rel=>$values) {
+      foreach($values as $i=>$value) {
+        $value = \mf2\resolveUrl($result['url'], $value);
+        $rels[$rel][$i] = $value;
+      }
+    }
+
+    return $this->respond($response, 200, [
+      'url' => $result['url'],
+      'code' => $result['code'],
+      'rels' => $rels
+    ]);
+  }
+
+}

public/index.php

@@ -24,6 +24,8 @@ $router->addRoute('GET', '/parse', 'Parse::parse');
 $router->addRoute('POST', '/parse', 'Parse::parse');
 $router->addRoute('POST', '/token', 'Token::token');
 
+$router->addRoute('GET', '/rels', 'Rels::fetch');
+
 $router->addRoute('GET', '/cert', 'Certbot::index');
 $router->addRoute('GET', '/cert/auth', 'Certbot::start_auth');
 $router->addRoute('GET', '/cert/logout', 'Certbot::logout');