move avatar logic out of controller to an own PORO: AvatarGenerator

app/controllers/users_controller.rb

@@ -66,14 +66,12 @@ def update
   end
 
   def update_avatar
-    avatar = params[:avatar]
-    errors = validate_avatar(avatar)
+    operation = AvatarGenerator.new(current_user, params)
 
-    if errors.blank?
-      current_user.avatar.purge if current_user.avatar.attached?
-      crop_image_and_save(current_user, avatar)
+    if operation.errors.empty?
+      operation.call
     else
-      flash[:error] = errors.join("<br>")
+      flash[:error] = operation.errors.join("<br>")
     end
 
     redirect_to current_user
@@ -130,38 +128,4 @@ def redirect_to_after_create
                                  name: @user.username)
     end
   end
-
-  def crop_image_and_save(user, avatar)
-    orig_width = params[:original_width].to_i
-    width      = params[:height_width].to_i
-    left       = params[:width_offset].to_i
-    top        = params[:height_offset].to_i
-
-    image_processed = ImageProcessing::MiniMagick.
-                      source(avatar.tempfile).
-                      resize_to_fit(orig_width, nil).
-                      crop("#{width}x#{width}+#{left}+#{top}!").
-                      convert("png").
-                      call
-
-    user.avatar.attach(
-      io: image_processed,
-      filename: user.username,
-      content_type: avatar.content_type
-    )
-  end
-
-  def validate_avatar(file)
-    errors = []
-
-    if User::AVATAR_CONTENT_TYPES.exclude?(file.content_type)
-      errors << t("users.show.invalid_format")
-    end
-
-    if file.size.to_f > User::AVATAR_MAX_SIZE.megabytes
-      errors << t("users.avatar.max_size_warning", size: User::AVATAR_MAX_SIZE)
-    end
-
-    errors
-  end
 end

app/models/user.rb

@@ -9,8 +9,6 @@ class User < ApplicationRecord
     :timeoutable
   ]
 
-  AVATAR_MAX_SIZE = 5
-  AVATAR_CONTENT_TYPES = %w[image/jpeg image/pjpeg image/png image/x-png]
   GENDERS = %w(
     female
     male

app/services/avatar_generator.rb

@@ -0,0 +1,51 @@
+class AvatarGenerator
+  MAX_SIZE = 5
+  CONTENT_TYPES = %w[image/jpeg image/pjpeg image/png image/x-png]
+
+  attr_accessor :errors
+
+  def initialize(user, params)
+    @user   = user
+    @params = params
+    @avatar = params[:avatar]
+    @errors = []
+
+    validate_avatar
+  end
+
+  def call
+    @user.avatar.purge if @user.avatar.attached?
+
+    @user.avatar.attach(
+      io: process_image,
+      filename: @user.username,
+      content_type: @avatar.content_type
+    )
+  end
+
+  private
+
+  def process_image
+    orig_width = @params[:original_width].to_i
+    width      = @params[:height_width].to_i
+    left       = @params[:width_offset].to_i
+    top        = @params[:height_offset].to_i
+
+    ImageProcessing::MiniMagick.
+      source(@avatar.tempfile).
+      resize_to_fit(orig_width, nil).
+      crop("#{width}x#{width}+#{left}+#{top}!").
+      convert("png").
+      call
+  end
+
+  def validate_avatar
+    if CONTENT_TYPES.exclude?(@avatar.content_type)
+      @errors << I18n.t("users.show.invalid_format")
+    end
+
+    if @avatar.size.to_f > MAX_SIZE.megabytes
+      @errors << I18n.t("users.avatar.max_size_warning", size: MAX_SIZE)
+    end
+  end
+end

spec/controllers/users_controller_spec.rb

@@ -433,7 +433,7 @@
       end
 
       it "don't change the photo attached if the file size it too big" do
-        allow_any_instance_of(ActionDispatch::Http::UploadedFile).to receive(:size) { User::AVATAR_MAX_SIZE.megabytes + 1.megabyte }
+        allow_any_instance_of(ActionDispatch::Http::UploadedFile).to receive(:size) { AvatarGenerator::MAX_SIZE.megabytes + 1.megabyte }
 
         put :update_avatar, params: { avatar: uploaded_file }