media assets: allow assets to be regenerated.

Add a `MediaAsset#regenerate!` method that regenerates everything about
the asset, including the metadata, thumbnails, IQDB, cached Cloudflare
URLs, and AI tags.

Fixes it so that a) it's possible to regenerate media assets that aren't
attached to posts and b) regenerating a post regenerates everything. Before
it didn't regenerate the metadata, AI tags, or all of the cached URLs.

app/models/media_asset.rb

@@ -320,13 +320,53 @@ class MediaAsset < ApplicationRecord
       self.duration = media_file.duration
     end
 
-    def regenerate_ai_tags!
+    def regenerate!(metadata: true, files: true, ai_tags: true)
       with_lock do
-        ai_tags.each(&:destroy!)
-        update!(ai_tags: generate_ai_tags)
+        variant("original").open_file! do |original_file|
+          regenerate_metadata!(original_file) if metadata
+          regenerate_files!(original_file) if files
+        end
+
+        regenerate_ai_tags! if ai_tags
       end
     end
 
+    # Regenerate all metadata for the asset, including the md5, width, height, file size, file ext,
+    # duration, and EXIF metadata, both on the media asset and on the post. This may change the tags
+    # as well if the new metadata causes automatic tags to be recalculated.
+    def regenerate_metadata!(original_file)
+      update!(file: original_file)
+      media_metadata.update!(file: original_file)
+
+      if saved_changes? && post.present?
+        CurrentUser.scoped(User.system) do
+          post.update!(md5: md5, file_ext: file_ext, file_size: file_size, image_width: image_width, image_height: image_height)
+        end
+      end
+    end
+
+    # Regenerate all thumbnail and sample image files for the asset.
+    def regenerate_files!(original_file)
+      distribute_files!(original_file)
+      purge_cached_urls!
+      post.update_iqdb if post.present?
+    end
+
+    # Purge all image URLs from Cloudflare.
+    def purge_cached_urls!
+      urls = variants.map(&:file_url)
+      urls += [post.tagged_file_url(tagged_filenames: true), post.tagged_large_file_url(tagged_filenames: true)] if post.present?
+
+      CloudflareService.new.purge_cache(urls.uniq)
+    end
+
+    # Regenerate the AI tags for the asset. This is based on the 360x360 thumbnail, so the files
+    # should be regenerated first in case the thumbnail changed.
+    def regenerate_ai_tags!
+      ai_tags.each(&:destroy!)
+      update!(ai_tags: generate_ai_tags)
+    end
+
     def generate_ai_tags
       return [] if !has_variant?("360x360")
 

app/models/post.rb

@@ -1454,38 +1454,11 @@ class Post < ApplicationRecord
 
         ModAction.log("regenerated IQDB for post ##{id}", :post_regenerate_iqdb, subject: self, user: user)
       else
-        media_file = media_asset.variant(:original).open_file
-        media_asset.distribute_files!(media_file)
-
-        update!(
-          image_width: media_file.width,
-          image_height: media_file.height,
-          file_size: media_file.file_size,
-          file_ext: media_file.file_ext
-        )
-
-        media_asset.update!(
-          image_width: media_file.width,
-          image_height: media_file.height,
-          file_size: media_file.file_size,
-          file_ext: media_file.file_ext
-        )
-
-        purge_cached_urls!
-        update_iqdb
+        media_asset.regenerate!
 
         ModAction.log("regenerated image samples for post ##{id}", :post_regenerate, subject: self, user: user)
       end
     end
-
-    def purge_cached_urls!
-      urls = [
-        preview_file_url, large_file_url, file_url,
-        tagged_file_url(tagged_filenames: true), tagged_large_file_url(tagged_filenames: true),
-      ]
-
-      CloudflareService.new.purge_cache(urls)
-    end
   end
 
   concerning :IqdbMethods do