#399

backend/app/models/post.rb

@@ -2,6 +2,8 @@ class Post < ApplicationRecord
   require 'mini_magick'
   require 'stringio'
 
+  class RemoteThumbnailFetchFailed < StandardError; end
+
   ORIGINAL_CREATED_INVALID_MESSAGE = 'オリジナルの作成日時の形式が不正です．'.freeze
   ORIGINAL_CREATED_MINUTE_PRECISION_MESSAGE =
       'オリジナルの作成日時は分単位で入力してください．'.freeze
@@ -12,7 +14,9 @@ class Post < ApplicationRecord
   def self.resized_thumbnail_attachment(upload)
     upload.rewind
     image = MiniMagick::Image.read(upload.read)
-    image.resize '180x180'
+    image.resize '180x180^'
+    image.gravity 'Center'
+    image.extent '180x180'
     image.format 'jpg'
 
     { io: StringIO.new(image.to_blob),
@@ -125,7 +129,11 @@ class Post < ApplicationRecord
           '%d:%02d' % [min, s]
         end
 
-    remainder_ms.positive? ? "#{ base }.#{ remainder_ms.to_s.rjust(3, '0') }" : base
+    if remainder_ms.positive?
+      "#{ base }.#{ remainder_ms.to_s.rjust(3, '0') }"
+    else
+      base
+    end
   end
 
   def snapshot_parent_post_ids = parents.order(:id).pluck(:id)
@@ -147,8 +155,33 @@ class Post < ApplicationRecord
     thumbnail.attach(self.class.resized_thumbnail_attachment(StringIO.new(thumbnail.download)))
   end
 
+  def attach_thumbnail_from_url! raw_url
+    response = Preview::ThumbnailFetcher.fetch_image_response(raw_url)
+    thumbnail.attach(
+        io: StringIO.new(response.body),
+        filename: remote_thumbnail_filename(response.url),
+        content_type: response.content_type)
+    resized_thumbnail!
+  rescue Preview::UrlSafety::UnsafeUrl,
+         Preview::ThumbnailFetcher::GenerationFailed,
+         Preview::HttpFetcher::FetchFailed,
+         Preview::HttpFetcher::FetchTimeout,
+         Preview::HttpFetcher::ResponseTooLarge,
+         MiniMagick::Error => e
+    raise RemoteThumbnailFetchFailed, e.message
+  end
+
   private
 
+  def remote_thumbnail_filename url
+    filename = File.basename(URI.parse(url).path.to_s)
+    return filename if filename.present? && filename != '/'
+
+    'thumbnail'
+  rescue URI::InvalidURIError
+    'thumbnail'
+  end
+
   def validate_original_created_range
     f = parse_original_created_value(:original_created_from)
     b = parse_original_created_value(:original_created_before)