Merge pull request #63 from rails/variants

On-demand variants

1 files changed, 35 insertions, 0 deletions

diff --git a/lib/active_storage/variant.rb b/lib/active_storage/variant.rb
new file mode 100644
index 0000000000..435033f980
--- /dev/null
+++ b/lib/active_storage/variant.rb
@@ -0,0 +1,35 @@
+require "active_storage/blob"
+require "mini_magick"
+
+# Image blobs can have variants that are the result of a set of transformations applied to the original.
+class ActiveStorage::Variant
+  attr_reader :blob, :variation
+  delegate :service, to: :blob
+
+  def initialize(blob, variation)
+    @blob, @variation = blob, variation
+  end
+
+  def processed
+    process unless service.exist?(key)
+    self
+  end
+
+  def key
+    "variants/#{blob.key}/#{variation.key}"
+  end
+
+  def url(expires_in: 5.minutes, disposition: :inline)
+    service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename
+  end
+
+
+  private
+    def process
+      service.upload key, transform(service.download(blob.key))
+    end
+
+    def transform(io)
+      File.open MiniMagick::Image.read(io).tap { |image| variation.transform(image) }.path
+    end
+end