use JS IntersectionObserver to lazy load youtube videos

app/models.py

@@ -1072,13 +1072,14 @@ class Post(db.Model):
             file = File.query.get(self.image_id)
             file.delete_from_disk()
 
-    def youtube_embed(self) -> str:
+    def youtube_embed(self, rel=True) -> str:
         if self.url:
             parsed_url = urlparse(self.url)
             query_params = parse_qs(parsed_url.query)
 
             if 'v' in query_params:
                 video_id = query_params.pop('v')[0]
+                if rel:
                     query_params['rel'] = '0'
                 new_query = urlencode(query_params, doseq=True)
                 return f'{video_id}?{new_query}'
@@ -1087,6 +1088,7 @@ class Post(db.Model):
                 video_id = parsed_url.path.split('/shorts/')[1].split('/')[0]
                 if 't' in query_params:
                     query_params['start'] = query_params.pop('t')[0]
+                if rel:
                     query_params['rel'] = '0'
                 new_query = urlencode(query_params, doseq=True)
                 return f'{video_id}?{new_query}'

app/static/js/scripts.js

@@ -10,6 +10,7 @@ if(!setTheme) {
 
 // fires after DOM is ready for manipulation
 document.addEventListener("DOMContentLoaded", function () {
+    setupYouTubeLazyLoad();
     setupCommunityNameInput();
     setupShowMoreLinks();
     setupConfirmFirst();
@@ -27,6 +28,42 @@ document.addEventListener("DOMContentLoaded", function () {
     setupLightboxPostBody();
 });
 
+function setupYouTubeLazyLoad() {
+    const lazyVideos = document.querySelectorAll(".video-wrapper");
+
+    if ("IntersectionObserver" in window) {
+        let videoObserver = new IntersectionObserver((entries, observer) => {
+            entries.forEach((entry) => {
+                if (entry.isIntersecting) {
+                    let videoWrapper = entry.target;
+                    let iframe = document.createElement("iframe");
+                    iframe.src = videoWrapper.getAttribute("data-src");
+                    iframe.allow = "accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; fullscreen";
+
+                    videoWrapper.innerHTML = "";
+                    videoWrapper.appendChild(iframe);
+
+                    videoObserver.unobserve(videoWrapper);
+                }
+            });
+        });
+
+        lazyVideos.forEach((video) => {
+            videoObserver.observe(video);
+        });
+    } else {
+        // Fallback for older browsers
+        lazyVideos.forEach((video) => {
+            let iframe = document.createElement("iframe");
+            iframe.src = video.getAttribute("data-src");
+            iframe.allow = "accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; fullscreen";
+
+            video.innerHTML = "";
+            video.appendChild(iframe);
+        });
+    }
+}
+
 // All elements with the class "showElement" will show the DOM element referenced by the data-id attribute
 function setupShowElementLinks() {
     var elements = document.querySelectorAll('.showElement');

app/static/styles.css

@@ -911,6 +911,31 @@ div.navbar {
   background-color: white;
   opacity: 0.5;
 }
+.post_teaser_video_preview .video-wrapper {
+  position: relative;
+  padding-bottom: 56.25%;
+  /* 16:9 aspect ratio */
+  height: 0;
+  overflow: hidden;
+  background-color: #000;
+}
+.post_teaser_video_preview .video-wrapper img {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+  cursor: pointer;
+}
+.post_teaser_video_preview .video-wrapper iframe {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+  border: 0;
+}
 
 .max_width_512 {
   max-width: 512px;

app/static/styles.scss

@@ -503,6 +503,33 @@ div.navbar {
     background-color: white;
     opacity: 0.5;
   }
+
+  .video-wrapper {
+    position: relative;
+    padding-bottom: 56.25%; /* 16:9 aspect ratio */
+    height: 0;
+    overflow: hidden;
+    background-color: #000;
+  }
+
+  .video-wrapper img {
+      position: absolute;
+      top: 0;
+      left: 0;
+      width: 100%;
+      height: 100%;
+      object-fit: cover;
+      cursor: pointer;
+  }
+
+  .video-wrapper iframe {
+      position: absolute;
+      top: 0;
+      left: 0;
+      width: 100%;
+      height: 100%;
+      border: 0;
+  }
 }
 
 .max_width_512 {

app/templates/post/post_teaser/_video.html

@@ -43,7 +43,9 @@
                     <div style="padding-bottom: 56.25%; position: relative;"><iframe style="position: absolute; top: 0px; left: 0px; width: 100%; height: 100%;" src="{{ post.url.replace('redgifs.com/watch/', 'redgifs.com/ifr/') }}" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture; fullscreen"  width="100%" height="100%" frameborder="0"></iframe></div>
                 {% endif -%}
                 {% if 'youtube.com' in post.url -%}
-                    <div style="padding-bottom: 56.25%; position: relative;"><iframe style="position: absolute; top: 0px; left: 0px; width: 100%; height: 100%;" src="https://www.youtube.com/embed/{{ post.youtube_embed() }}" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture; fullscreen"  width="100%" height="100%" frameborder="0"></iframe></div>
+                    <div class="video-wrapper" data-src="https://www.youtube.com/embed/{{ post.youtube_embed() }}">
+                        <img src="https://img.youtube.com/vi/{{ post.youtube_embed(rel=False) }}/hqdefault.jpg" alt="Video Thumbnail">
+                    </div>
                 {% endif -%}
                 {% if 'videos/watch' in post.url -%}
                     <div style="padding-bottom: 56.25%; position: relative;"><iframe style="position: absolute; top: 0px; left: 0px; width: 100%; height: 100%;" src="{{ post.peertube_embed() }}" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture; fullscreen"  width="100%" height="100%" frameborder="0"></iframe></div>