#306

backend/app/services/material_thumbnail_generator.rb

@@ -11,25 +11,30 @@ class MaterialThumbnailGenerator
   class << self
     def generate! material
       new(material).generate!
-    rescue ActiveStorage::FileNotFoundError, ArgumentError, MiniMagick::Error => e
-      Rails.logger.warn("Material thumbnail generation skipped: #{ e.class }: #{ e.message }")
-      nil
     end
   end
 
   def initialize material
     @material = material
+    @ffmpeg_stderr = []
   end
 
   def generate!
-    @material.thumbnail.purge if @material.thumbnail.attached?
-    return unless @material.file.attached?
-    return unless image? || video?
+    return log_result(:no_file) unless @material.file.attached?
+    return log_result(:unsupported_content_type) unless image? || video?
 
     @material.file.blob.open do |file|
       thumbnail = image? ? image_thumbnail(file.path) : video_thumbnail(file.path)
-      attach_thumbnail(thumbnail) if thumbnail
+      return log_result(:generation_failed) unless thumbnail
+
+      return attach_thumbnail(thumbnail)
     end
+  rescue ActiveStorage::FileNotFoundError => e
+    log_result(:file_not_found, error: e)
+  rescue MiniMagick::Error => e
+    log_result(:mini_magick_error, error: e)
+  rescue ArgumentError, StandardError => e
+    log_result(:generation_failed, error: e)
   end
 
   private
@@ -38,7 +43,11 @@ class MaterialThumbnailGenerator
 
   def video? = content_type.start_with?('video/')
 
-  def content_type = @material.file.blob.content_type.to_s
+  def content_type
+    return nil unless @material.file.attached?
+
+    @material.file.blob.content_type.to_s
+  end
 
   def image_thumbnail path
     image = MiniMagick::Image.open(path)
@@ -71,16 +80,47 @@ class MaterialThumbnailGenerator
                        '-frames:v', '1',
                        '-f', 'image2',
                        output_path)
-    Rails.logger.warn("ffmpeg thumbnail failed: #{ stderr }") unless status.success?
+    @ffmpeg_stderr << stderr if stderr.present?
     status.success?
   rescue Errno::ENOENT => e
-    Rails.logger.warn("ffmpeg unavailable for material thumbnail: #{ e.message }")
+    @ffmpeg_stderr << "ffmpeg unavailable: #{ e.message }"
     false
   end
 
   def attach_thumbnail image
-    @material.thumbnail.attach(io: File.open(image.path),
-                               filename: 'material-thumbnail.jpg',
-                               content_type: 'image/jpeg')
+    blob = nil
+    File.open(image.path) do |io|
+      blob = ActiveStorage::Blob.create_and_upload!(
+          io:,
+          filename: 'material-thumbnail.jpg',
+          content_type: 'image/jpeg')
+    end
+    @material.thumbnail.attach(blob)
+    log_result(:attached)
+  rescue StandardError => e
+    blob&.purge_later
+    log_result(:attach_failed, error: e)
+  end
+
+  def log_result result, error: nil
+    log_payload = { material_id: @material.id,
+                    file_blob_id: file_blob_id,
+                    content_type:,
+                    result:,
+                    error_class: error&.class&.name,
+                    error_message: error&.message,
+                    ffmpeg_stderr: @ffmpeg_stderr.join("\n").presence }
+    if [:attached, :no_file, :unsupported_content_type].include?(result)
+      Rails.logger.info("Material thumbnail generation: #{ log_payload.to_json }")
+    else
+      Rails.logger.warn("Material thumbnail generation: #{ log_payload.to_json }")
+    end
+    result
+  end
+
+  def file_blob_id
+    return nil unless @material.file.attached?
+
+    @material.file.blob.id
   end
 end