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<?php
namespace Digitigrade;
class LinkPreview implements \JsonSerializable {
public string $url;
public string $siteName;
public string $title;
public string $description;
public string $style;
public ?string $imageUrl = null;
/**
* Generates a link preview for the given URL.
* @param string $url
* @return LinkPreview|null the link preview, or null if none is available
*/
public static function generate(string $url): ?self {
$p = new self();
$p->url = $url;
return $p->update() ? $p : null;
}
/**
* Updates the information for this link preview.
* @return bool true if successful
*/
public function update(): bool {
if (!(str_starts_with($this->url, "https://") || str_starts_with($this->url, "http://"))) {
return false;
}
$d = new \DOMDocument();
$c = @file_get_contents($this->url);
if (!$c)
return false;
@$d->loadHTML($c);
$url = $this->url;
$siteName = hostname_from_uri($this->url);
$style = 'text';
$title = $d->getElementsByTagName('title')->item(0)?->textContent;
$metas = $d->getElementsByTagName('meta');
foreach ($metas as $tag) {
if ($tag->attributes->getNamedItem('name')?->textContent == 'description') {
// <meta name="description" content="...">
$description = $tag->attributes->getNamedItem('content')?->textContent;
} elseif ($prop = $tag->attributes->getNamedItem('property')) {
// <meta property="og:..." content="...">
$content = $tag->attributes->getNamedItem('content')?->textContent;
match ($prop->textContent) {
'og:title' => $title = $content,
'og:description' => $description = $content,
'og:url' => $url = $content,
'og:site_name' => $siteName = $content,
'og:image' => $imageUrl = $content,
default => null
};
} elseif ($tag->attributes->getNamedItem('name')?->textContent == 'twitter:card'
&& $tag->attributes->getNamedItem("content")?->textContent == 'summary_large_image') {
// <meta name="twitter:card" content="summary_large_image">
$style = 'largeImage';
}
}
// turn text into smallImage if an image is present
$style = ($style == 'text' && isset($imageUrl)) ? 'smallImage' : $style;
if (!isset($title, $description))
return false;
$this->url = $url;
$this->siteName = $siteName;
$this->title = $title;
$this->description = $description;
$this->style = $style;
$this->imageUrl = $imageUrl ?? null;
return true;
}
public function jsonSerialize(): array {
return [
'url' => $this->url,
'siteName' => $this->siteName,
'title' => $this->title,
'description' => $this->description,
'style' => $this->style,
'imageUrl' => $this->imageUrl
];
}
}
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