Allow to register more detectors

Author: oscarotero

README.md

@@ -250,6 +250,34 @@ $factory->removeAdapter('pinterest.com');
 $factory->setDefault(CustomExtractor::class);
 ```
 
+### Detectors
+
+Embed comes with several predefined detectors, but you may want to change or add more. Just create a class extending `Embed\Detectors\Detector` class and register it in the extractor factory. For example:
+
+```php
+use Embed\Embed;
+use Embed\Detectors\Detector;
+
+class Robots extends Detector
+{
+    public function detect(): ?string
+    {
+        $response = $this->extractor->getResponse();
+        $document = $this->extractor->getDocument();
+
+        return $response->getHeaderLine('x-robots-tag'),
+            ?: $document->meta('robots');
+    }
+}
+
+//Register the detector
+$embed = new Embed();
+$embed->getExtractorFactory()->addDetector('robots', Robots::class);
+
+//Use it
+$info = $embed->get('http://example.com');
+$robots = $info->robots;
+```
 ---
 
 If this library is useful for you, say thanks [buying me a beer :beer:](https://www.paypal.me/oscarotero)!

src/Extractor.php

@@ -43,6 +43,8 @@ class Extractor
     private OEmbed $oembed;
     private LinkedData $linkedData;
 
+    private array $customDetectors = [];
+
     protected AuthorName $authorName;
     protected AuthorUrl $authorUrl;
     protected Cms $cms;
@@ -99,7 +101,7 @@ public function __construct(UriInterface $uri, RequestInterface $request, Respon
 
     public function __get(string $name)
     {
-        $detector = $this->$name ?? null;
+        $detector = $this->customDetectors[$name] ?? $this->$name ?? null;
 
         if (!$detector || !($detector instanceof Detector)) {
             throw new DomainException(sprintf('Invalid key "%s". No detector found for this value', $name));
@@ -108,6 +110,11 @@ public function __get(string $name)
         return $detector->get();
     }
 
+    public function addDetector(string $name, Detector $detector): void
+    {
+        $this->customDetectors[$name] = $detector;
+    }
+
     public function getDocument(): Document
     {
         return $this->document;

src/ExtractorFactory.php

@@ -30,6 +30,7 @@ class ExtractorFactory
         'imagizer.imageshack.com' => Adapters\ImageShack\Extractor::class,
         'youtube.com' => Adapters\Youtube\Extractor::class,
     ];
+    private array $customDetectors = [];
 
     public function createExtractor(UriInterface $uri, RequestInterface $request, ResponseInterface $response, Crawler $crawler): Extractor
     {
@@ -38,14 +39,25 @@ public function createExtractor(UriInterface $uri, RequestInterface $request, Re
 
         $class = $this->adapters[$host] ?? $this->default;
 
-        return new $class($uri, $request, $response, $crawler);
+        $extractor = new $class($uri, $request, $response, $crawler);
+
+        foreach ($this->customDetectors as $name => $detector) {
+            $extractor->addDetector($name, new $detector($extractor));
+        }
+
+        return $extractor;
     }
 
     public function addAdapter(string $pattern, string $class): void
     {
         $this->adapters[$pattern] = $class;
     }
 
+    public function addDetector(string $name, string $class): void
+    {
+        $this->customDetectors[$name] = $class;
+    }
+
     public function removeAdapter(string $pattern): void
     {
         unset($this->adapters[$pattern]);