Very incomplete first stab

5 files changed, 112 insertions, 24 deletions

diff --git a/lib/active_storage/controllers/variants_controller.rb b/lib/active_storage/controllers/variants_controller.rb
new file mode 100644
index 0000000000..24cee16e80
--- /dev/null
+++ b/lib/active_storage/controllers/variants_controller.rb
@@ -0,0 +1,22 @@
+require "action_controller"
+require "active_storage/blob"
+
+class ActiveStorage::Controllers::VariantsController < ActionController::Base
+  def show
+    if blob_key = decode_verified_key
+      variant = ActiveStorage::Variant.lookup(blob_key: blob_key, variation_key: params[:variation_key])
+      redirect_to variant.url
+    else
+      head :not_found
+    end
+  end
+
+  private
+    def decode_verified_key
+      ActiveStorage::VerifiedKeyWithExpiration.decode(params[:encoded_key])
+    end
+
+    def disposition_param
+      params[:disposition].presence_in(%w( inline attachment )) || 'inline'
+    end
+end
diff --git a/lib/active_storage/engine.rb b/lib/active_storage/engine.rb
index c251f522c6..8918b179e0 100644
--- a/lib/active_storage/engine.rb
+++ b/lib/active_storage/engine.rb
@@ -33,29 +33,42 @@ module ActiveStorage
       end
     end
 
-    config.after_initialize do |app|
-      if config_choice = app.config.active_storage.service
-        config_file = Pathname.new(Rails.root.join("config/storage_services.yml"))
-        raise("Couldn't find Active Storage configuration in #{config_file}") unless config_file.exist?
-
-        require "yaml"
-        require "erb"
-
-        configs =
-          begin
-            YAML.load(ERB.new(config_file.read).result) || {}
-          rescue Psych::SyntaxError => e
-            raise "YAML syntax error occurred while parsing #{config_file}. " \
-                  "Please note that YAML must be consistently indented using spaces. Tabs are not allowed. " \
-                  "Error: #{e.message}"
-          end
-
-        ActiveStorage::Blob.service =
-          begin
-            ActiveStorage::Service.configure config_choice, configs
-          rescue => e
-            raise e, "Cannot load `Rails.config.active_storage.service`:\n#{e.message}", e.backtrace
-          end
+    initializer "active_storage.verifiers" do
+      require "active_storage/verified_key_with_expiration"
+      require "active_storage/variant"
+
+      config.after_initialize do |app|
+        ActiveStorage::VerifiedKeyWithExpiration.verifier = \
+        ActiveStorage::Variant.verifier = \
+          Rails.application.message_verifier('ActiveStorage')
+      end
+    end
+
+    initializer "active_storage.services" do
+      config.after_initialize do |app|
+        if config_choice = app.config.active_storage.service
+          config_file = Pathname.new(Rails.root.join("config/storage_services.yml"))
+          raise("Couldn't find Active Storage configuration in #{config_file}") unless config_file.exist?
+
+          require "yaml"
+          require "erb"
+
+          configs =
+            begin
+              YAML.load(ERB.new(config_file.read).result) || {}
+            rescue Psych::SyntaxError => e
+              raise "YAML syntax error occurred while parsing #{config_file}. " \
+                    "Please note that YAML must be consistently indented using spaces. Tabs are not allowed. " \
+                    "Error: #{e.message}"
+            end
+
+          ActiveStorage::Blob.service =
+            begin
+              ActiveStorage::Service.configure config_choice, configs
+            rescue => e
+              raise e, "Cannot load `Rails.config.active_storage.service`:\n#{e.message}", e.backtrace
+            end
+        end
       end
     end
   end
diff --git a/lib/active_storage/routes.rb b/lib/active_storage/routes.rb
index 748427a776..fade234ad3 100644
--- a/lib/active_storage/routes.rb
+++ b/lib/active_storage/routes.rb
@@ -1,2 +1,3 @@
 get  "/rails/active_storage/disk/:encoded_key/*filename" => "active_storage/disk#show", as: :rails_disk_blob
+get  "/rails/active_storage/variants/:encoded_key/:encoded_transformation/*filename" => "active_storage/controllers/variants#show", as: :rails_blob_variant
 post "/rails/active_storage/direct_uploads" => "active_storage/direct_uploads#create", as: :rails_direct_uploads
diff --git a/lib/active_storage/variant.rb b/lib/active_storage/variant.rb
new file mode 100644
index 0000000000..9b9dad43da
--- /dev/null
+++ b/lib/active_storage/variant.rb
@@ -0,0 +1,52 @@
+require "active_storage/blob"
+require "mini_magick"
+
+class ActiveStorage::Variant
+  class_attribute :verifier
+
+  attr_reader :blob, :variation
+  delegate :service, to: :blob
+
+  def self.lookup(blob_key:, variation_key:)
+    new ActiveStorage::Blob.find_by!(key: blob_key), variation: verifier.verify(variation_key)
+  end
+
+  def self.encode_key(variation)
+    verifier.generate(variation)
+  end
+
+  def initialize(blob, variation:)
+    @blob, @variation = blob, variation
+  end
+
+  def url(expires_in: 5.minutes, disposition: :inline)
+    perform unless exist?
+    service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename
+  end
+
+  def key
+    verifier.generate(variation)
+  end
+
+  private
+    def perform
+      upload_variant transform(download_blob)
+    end
+
+    def download_blob
+      service.download(blob.key)
+    end
+
+    def upload_variant(variation)
+      service.upload key, variation
+    end
+
+    def transform(io)
+      # FIXME: Actually do a variant based on the variation
+      File.open MiniMagick::Image.read(io).resize("500x500").path
+    end
+
+    def exist?
+      service.exist?(key)
+    end
+end
diff --git a/lib/active_storage/verified_key_with_expiration.rb b/lib/active_storage/verified_key_with_expiration.rb
index 8708106735..4a46483db5 100644
--- a/lib/active_storage/verified_key_with_expiration.rb
+++ b/lib/active_storage/verified_key_with_expiration.rb
@@ -1,5 +1,5 @@
 class ActiveStorage::VerifiedKeyWithExpiration
-  class_attribute :verifier, default: defined?(Rails) ? Rails.application.message_verifier('ActiveStorage') : nil
+  class_attribute :verifier
 
   class << self
     def encode(key, expires_in: nil)