feat: Add video embedding for YouTube and Vimeo links in PostCard.

src/app/globals.css

@@ -338,6 +338,25 @@ a.btn-primary:visited {
   display: block;
 }
 
+.video-embed-container {
+  position: relative;
+  padding-bottom: 56.25%; /* 16:9 aspect ratio */
+  height: 0;
+  overflow: hidden;
+  border-radius: var(--radius-md);
+  margin-bottom: 12px;
+  border: 1px solid var(--border);
+  background: #000;
+}
+
+.video-embed-container iframe {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+}
+
 .post-actions {
   display: flex;
   gap: 24px;

src/components/PostCard.tsx

@@ -5,6 +5,7 @@ import Link from 'next/link';
 import { HeartIcon, RepeatIcon, MessageIcon, FlagIcon, TrashIcon } from '@/components/Icons';
 import { Post } from '@/lib/types';
 import { useAuth } from '@/lib/contexts/AuthContext';
+import { VideoEmbed } from '@/components/VideoEmbed';
 
 interface PostCardProps {
     post: Post;
@@ -181,6 +182,10 @@ export function PostCard({ post, onLike, onRepost, onComment, onDelete, isDetail
             )}
 
             {post.linkPreviewUrl && (
+                <VideoEmbed url={post.linkPreviewUrl} />
+            )}
+
+            {post.linkPreviewUrl && !post.linkPreviewUrl.match(/(youtube\.com|youtu\.be|vimeo\.com)/) && (
                 <a
                     href={post.linkPreviewUrl}
                     target="_blank"

src/components/VideoEmbed.tsx

@@ -0,0 +1,52 @@
+'use client';
+
+interface VideoEmbedProps {
+    url: string;
+}
+
+export function VideoEmbed({ url }: VideoEmbedProps) {
+    const getYouTubeId = (url: string) => {
+        const regExp = /^.*(youtu.be\/|v\/|u\/\w\/|embed\/|watch\?v=|\&v=)([^#\&\?]*).*/;
+        const match = url.match(regExp);
+        return (match && match[2].length === 11) ? match[2] : null;
+    };
+
+    const getVimeoId = (url: string) => {
+        const regExp = /(?:www\.|player\.)?vimeo.com\/(?:channels\/(?:\w+\/)?|groups\/(?:[^\/]*)\/videos\/|album\/(?:\d+)\/video\/|video\/|)(\d+)(?:$|\/|\?)/;
+        const match = url.match(regExp);
+        return match ? match[1] : null;
+    };
+
+    const youtubeId = getYouTubeId(url);
+    const vimeoId = getVimeoId(url);
+
+    if (youtubeId) {
+        return (
+            <div className="video-embed-container">
+                <iframe
+                    src={`https://www.youtube.com/embed/${youtubeId}`}
+                    title="YouTube video player"
+                    frameBorder="0"
+                    allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
+                    allowFullScreen
+                ></iframe>
+            </div>
+        );
+    }
+
+    if (vimeoId) {
+        return (
+            <div className="video-embed-container">
+                <iframe
+                    src={`https://player.vimeo.com/video/${vimeoId}`}
+                    title="Vimeo video player"
+                    frameBorder="0"
+                    allow="autoplay; fullscreen; picture-in-picture"
+                    allowFullScreen
+                ></iframe>
+            </div>
+        );
+    }
+
+    return null;
+}