link previews

2 files changed, 135 insertions, 1 deletions

diff --git a/Digitigrade/LinkPreview.php b/Digitigrade/LinkPreview.php
new file mode 100644
index 0000000..4716cc8
--- /dev/null
+++ b/Digitigrade/LinkPreview.php
@@ -0,0 +1,91 @@
+<?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
+        ];
+    }
+}
\ No newline at end of file
diff --git a/Digitigrade/Model/Note.php b/Digitigrade/Model/Note.php
index d5d4e69..ac9cc3c 100644
--- a/Digitigrade/Model/Note.php
+++ b/Digitigrade/Model/Note.php
@@ -4,12 +4,16 @@ namespace Digitigrade\Model;
 use Digitigrade\Db;
 use Digitigrade\FormattingProvider\CommonMark;
 use Digitigrade\FormattingProvider\SanitisedHtml;
+use Digitigrade\LinkPreview;
 use Digitigrade\Model\HomeTimelineItem;
 use Digitigrade\Notification\Notifyable;
 use Digitigrade\Timeline\TimelineIncludeable;
 use Digitigrade\Timeline\TimelineItem;
+use JsonMapper;
 
 class Note extends PushableModel implements TimelineIncludeable, Notifyable {
+    public const EXTENSION_LINK_PREVIEWS = 'https://pawpub.entities.org.uk/extension/link-previews';
+
     public ?int $id;
     public string $uri;
     public \DateTimeImmutable $created;
@@ -265,6 +269,45 @@ class Note extends PushableModel implements TimelineIncludeable, Notifyable {
         return htmlspecialchars($this->plainContent);
     }
 
+    /**
+     * Gets a list of LinkPreviews applicable to this note
+     * @return LinkPreview[]
+     */
+    public function getLinkPreviews(): array {
+        if (($this->extensions[self::EXTENSION_LINK_PREVIEWS] ?? []) == []) {
+            return [];
+        }
+        $mapper = new JsonMapper();
+        $results = [];
+        foreach ($this->extensions[self::EXTENSION_LINK_PREVIEWS] as $preview) {
+            $results[] = $mapper->map($preview, LinkPreview::class);
+        }
+        return $results;
+    }
+
+    /**
+     * Generates new LinkPreviews for this note (but does not save them automatically)
+     * @return LinkPreview[] the new link previews
+     */
+    public function generateLinkPreviews(): array {
+        $matches = [];
+        preg_match_all(
+            '`[a-z+]+://[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b(([-a-zA-Z0-9@:(%_\+.~#?&/=]|\)[^\s])*)`',
+            $this->getFormattedContent('text/markdown') ?? $this->plainContent,
+            $matches
+        );
+        $urls = $matches[0] ?? [];
+        $previews = array_filter(
+            array_map(fn($url) => LinkPreview::generate($url), $urls),
+            fn($p) => $p != null
+        );
+        $this->extensions[self::EXTENSION_LINK_PREVIEWS] = array_map(
+            fn($p) => json_decode(json_encode($p)),
+            $previews
+        );
+        return $previews;
+    }
+
     public function renderAsHtml() {
         render_template('note', ['note' => $this]);
     }
@@ -345,7 +388,7 @@ class Note extends PushableModel implements TimelineIncludeable, Notifyable {
                     'description' => $attachment->description
                 ];
             }, $this->attachments),
-            //'extensions' => []
+            'extensions' => $this->extensions
         ];
     }
 }
\ No newline at end of file