Add fields for talk YouTube video URL and video image

The image of a YouTube video is automatically downloaded when the talk
is saved through the Django admin. This allows serving the video
thumbnail without tracking the user by YouTube.

Author: jsmitka

program/admin.py

@@ -1,5 +1,11 @@
+from pathlib import PurePath
+from urllib.parse import quote
+
+import requests
 from django.contrib import admin
+from django.core.files.base import ContentFile
 from django.db import transaction
+from django.utils.html import format_html
 
 from program import pretalx, pretalx_sync
 from program.models import Room, Slot, Speaker, Talk, Utility, Workshop
@@ -140,7 +146,6 @@ class TalkAdmin(admin.ModelAdmin):
                 "fields": [
                     "pretalx_code",
                     "og_image",
-                    "video_id",
                 ],
             },
         ),
@@ -153,6 +158,15 @@ class TalkAdmin(admin.ModelAdmin):
                 ],
             },
         ),
+        (
+            "Slides and Video",
+            {
+                "fields": [
+                    "video_url",
+                    "video_image_html",
+                ],
+            },
+        ),
         (
             "Talk info (edit in pretalx)",
             {
@@ -181,10 +195,29 @@ class TalkAdmin(admin.ModelAdmin):
         "minimum_python_knowledge",
         "minimum_topic_knowledge",
         "type",
+        "video_image_html",
     ]
     actions = [make_public, make_not_public, talk_update_from_pretalx]
     change_form_template = "program/admin/change_form_session.html"
 
+    @admin.display(description="Video Image")
+    def video_image_html(self, obj: Talk):
+        if not obj.video_image:
+            return "(no image)"
+
+        html = (
+            '<a href="{image_url}" style="display: inline-block">'
+            '<img src="{image_url}" height="180"/><br>'
+            '<span style="display: inline-block; margin-top: 1ex;">{image_name}</span>'
+            "</a>"
+        )
+
+        return format_html(
+            html,
+            image_url=obj.video_image.url,
+            image_name=obj.video_image.name,
+        )
+
     def get_queryset(self, request):
         qs = super().get_queryset(request)
         qs = qs.prefetch_related("talk_speakers")
@@ -201,12 +234,52 @@ def get_readonly_fields(self, request, obj=None):
         return ro_fields
 
     def save_model(self, request, obj: Talk, form, change: bool) -> None:
+        if change:
+            self._update_video_image(obj)
+
         obj.save()
 
         if not change and obj.pretalx_code:
             sync = create_pretalx_sync()
             sync.update_talks([obj])
 
+    def _update_video_image(self, talk: Talk):
+        video_id = talk.video_id
+        if not video_id:
+            # Delete the existing image, if any.
+            if talk.video_image:
+                talk.video_image.delete(save=False)
+            return
+
+        # Get the video ID of the current image:
+        # the image is always named <video_id>.jpg
+        image_video_id: str | None = None
+        if talk.video_image:
+            image_path = PurePath(talk.video_image.name)
+            image_video_id = image_path.stem
+
+        # Check if the video ID has changed and download a new image when necessary.
+        if video_id != image_video_id:
+            image_data = self._download_youtube_video_image(video_id)
+            talk.video_image.save(
+                name=image_data.name,
+                content=image_data,
+                save=False,
+            )
+
+    def _download_youtube_video_image(self, video_id: str) -> ContentFile:
+        image_url = self._format_youtube_video_image_url(video_id)
+
+        with requests.get(image_url, timeout=30) as image_response:
+            image_response.raise_for_status()
+            return ContentFile(
+                content=image_response.content,
+                name=f"{video_id}.jpg",
+            )
+
+    def _format_youtube_video_image_url(self, video_id):
+        return f"https://img.youtube.com/vi/{quote(video_id)}/maxresdefault.jpg"
+
 
 @admin.action(description="Update from pretalx")
 def workshop_update_from_pretalx(modeladmin, request, queryset):

program/migrations/0022_talk_video.py

@@ -0,0 +1,46 @@
+# Generated by Django 4.2.1 on 2023-11-01 10:05
+
+import re
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("program", "0021_alter_room_options_remove_room_floor_room_order_and_more"),
+    ]
+
+    operations = [
+        migrations.RemoveField(
+            model_name="talk",
+            name="video_id",
+        ),
+        migrations.AddField(
+            model_name="talk",
+            name="video_image",
+            field=models.ImageField(
+                blank=True, null=True, upload_to="video-images/session/"
+            ),
+        ),
+        migrations.AddField(
+            model_name="talk",
+            name="video_url",
+            field=models.CharField(
+                blank=True,
+                help_text="YouTube video URL: <code>https://www.youtube.com/watch?v=&lt;VIDEO_ID&gt;</code>. Do not include any additional parameters, such as start time or tracking (UTM) parameters.",
+                max_length=1024,
+                null=True,
+                validators=[
+                    django.core.validators.RegexValidator(
+                        code="invalid_youtube_url",
+                        message="Invalid YouTube URL format.",
+                        regex=re.compile(
+                            "^https://www\\.youtube\\.com/watch\\?v=(?P<video_id>[0-9A-Za-z_-]{11,})$"
+                        ),
+                    )
+                ],
+                verbose_name="Video URL",
+            ),
+        ),
+    ]

program/models.py

@@ -1,12 +1,19 @@
 import datetime
+import re
 from typing import Any
 
+from django.core import validators
 from django.core.exceptions import ValidationError
 from django.db import models
 from django.urls import reverse
+from django.utils.safestring import mark_safe
 
 from program import pretalx
 
+YOUTUBE_VIDEO_PATTERN = re.compile(
+    pattern=r"^https://www\.youtube\.com/watch\?v=(?P<video_id>[0-9A-Za-z_-]{11,})$",
+)
+
 
 class Speaker(models.Model):
     PRETALX_FIELDS = [
@@ -242,10 +249,40 @@ def update_from_pretalx(self, pretalx_submission: dict[str, Any]) -> None:
 class Talk(Session):
     PRETALX_FIELDS = Session.PRETALX_FIELDS + ["is_keynote"]
 
-    video_id = models.CharField(
-        max_length=100, default="", blank=True, help_text="YouTube ID (from URL)"
-    )
     is_keynote = models.BooleanField(default=False, blank=True)
+    video_url = models.CharField(
+        max_length=1024,
+        null=True,
+        blank=True,
+        validators=[
+            validators.RegexValidator(
+                regex=YOUTUBE_VIDEO_PATTERN,
+                message="Invalid YouTube URL format.",
+                code="invalid_youtube_url",
+            ),
+        ],
+        verbose_name="Video URL",
+        help_text=mark_safe(
+            "YouTube video URL: "
+            "<code>https://www.youtube.com/watch?v=&lt;VIDEO_ID&gt;</code>. "
+            "Do not include any additional parameters, "
+            "such as start time or tracking (UTM) parameters."
+        ),
+    )
+    """
+    URL of the video with session recording. The URL should not contain any additional
+    parameters, such as start time or tracking (UTM) parameters.
+
+    Currently only YouTube videos are supported.
+    """
+    video_image = models.ImageField(
+        null=True,
+        blank=True,
+        upload_to="video-images/session/",
+    )
+    """
+    Image that will be used as a placeholder for the video.
+    """
 
     @property
     def speakers(self):
@@ -255,6 +292,15 @@ def speakers(self):
             return self.public_speakers
         return self.talk_speakers.all().filter(is_public=True)
 
+    @property
+    def video_id(self) -> str | None:
+        if not self.video_url:
+            return None
+        match = YOUTUBE_VIDEO_PATTERN.match(self.video_url)
+        if not match:
+            return None
+        return match.group("video_id")
+
     def update_from_pretalx(self, pretalx_submission: dict[str, Any]) -> None:
         # Note: remember to update the PRETALX_FIELDS class variable
         # when adding/removing fields synced with pretalx.