Search subdirs recursively for album cover candidates

Albums with no top-level photos (only sub-albums) now find a cover by
walking the full directory tree. Extracted cover_candidates() does a
recursive glob and returns paths relative to the album dir so the
existing thumb URL construction works unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/app.rb b/app.rb
index f5c52d4..f58a99d 100644
--- a/app.rb
+++ b/app.rb
@@ -123,12 +123,17 @@ helpers do
 
   def album_cover(dir, data)
     cover = data['cover']
-    if cover == '__random__'
-      candidates = Dir.children(dir).select { |n| (IMAGE_EXTS + VIDEO_EXTS).include?(File.extname(n).downcase.delete_prefix('.')) }
-      return candidates.sample
-    end
-    return cover if cover && File.exist?(File.join(dir, cover))
-    Dir.children(dir).sort.find { |n| (IMAGE_EXTS + VIDEO_EXTS).include?(File.extname(n).downcase.delete_prefix('.')) }
+    return cover if cover && cover != '__random__' && File.exist?(File.join(dir, cover))
+    candidates = cover_candidates(dir)
+    cover == '__random__' ? candidates.sample : candidates.first
+  end
+
+  def cover_candidates(dir)
+    exts = (IMAGE_EXTS + VIDEO_EXTS).to_set
+    Dir.glob(File.join(dir, '**', '*'))
+       .select { |f| File.file?(f) && exts.include?(File.extname(f).downcase.delete_prefix('.')) }
+       .sort
+       .map { |f| f.delete_prefix("#{dir}/") }
   end
 
   # Returns the absolute path or halts with 404.