Initial work for generating images with transparent background

app/controllers/calendars_controller.rb

@@ -1,6 +1,7 @@
 class CalendarsController < ApplicationController
+  include UserScoped
+
   def show
-    @user = User.find_by!(username: params[:user_username])
     @calendar = @user.calendars.fetch(params[:year])
 
     fresh_when [@user, @calendar]

app/controllers/concerns/user_scoped.rb

@@ -0,0 +1,13 @@
+module UserScoped
+  extend ActiveSupport::Concern
+
+  included do
+    before_action :set_user
+  end
+
+  private
+
+  def set_user
+    @user = User.find_by!(username: params[:user_username])
+  end
+end

app/controllers/images/calendars_controller.rb

@@ -0,0 +1,17 @@
+class Images::CalendarsController < ApplicationController
+  include UserScoped
+
+  def show
+    if small?
+      redirect_to @user.calendar_image.variant(:small)
+    else
+      redirect_to @user.calendar_image.variant(:large)
+    end
+  end
+
+  private
+
+  def small?
+    params[:variant] == "small"
+  end
+end

app/controllers/signatures_controller.rb

@@ -1,13 +1,7 @@
 class SignaturesController < ApplicationController
-  before_action :set_user
+  include UserScoped
 
   def show
-    redirect_to url_for(@user.signature)
-  end
-
-  private
-
-  def set_user
-    @user = User.with_attached_signature.find_by!(username: params[:user_username])
+    redirect_to @user.signature
   end
 end

app/controllers/timelines_controller.rb

@@ -1,6 +1,7 @@
 class TimelinesController < ApplicationController
+  include UserScoped
+
   def show
-    @user = User.find_by!(username: params[:user_username])
     @calendar = @user.calendars.fetch(params[:year])
 
     fresh_when [@user, @calendar]

app/models/user.rb

@@ -3,6 +3,7 @@ class User < ApplicationRecord
   include MALSyncable
   include Mergeable
   include Calendars
+  include CalendarImageable
   include Signaturable
   include Deactivatable
   include Geolocatable

app/models/user/calendar_imageable.rb

@@ -0,0 +1,23 @@
+module User::CalendarImageable
+  extend ActiveSupport::Concern
+
+  included do
+    has_one_attached :calendar_image do |attachable|
+      attachable.variant :large, resize_to_limit: [1200, 180], preprocessed: true
+      attachable.variant :small, resize_to_limit: [600, 150], preprocessed: true
+    end
+
+    after_create_commit :enqueue_calendar_images_generation
+    after_update_commit :enqueue_calendar_images_generation, if: -> { calendar_images.obsolete? }
+  end
+
+  def calendar_images
+    User::CalendarImages.new(self)
+  end
+
+  private
+
+  def enqueue_calendar_images_generation
+    calendar_images.generate_later
+  end
+end

app/models/user/calendar_images.rb

@@ -0,0 +1,73 @@
+require "image_processing/vips"
+
+class User::CalendarImages
+  def initialize(user)
+    super()
+    @user = user
+  end
+
+  def generate
+    Instrumentation.instrument(title: "#{self.class.name}#generate") do
+      user.with_time_zone { generate_from_activities }
+    end
+  end
+
+  def generate_later
+    User::CalendarImages::GenerateJob.perform_later(user)
+  end
+
+  def obsolete?
+    return true unless user.calendar_image.attached?
+    return true if user.saved_change_to_checksum?
+
+    user.calendar_image.blob.created_at.in_time_zone.to_date != Time.zone.today
+  end
+
+  class GenerateJob < ApplicationJob
+    retry_on(*BrowserSession::RETRYABLE_ERRORS, attempts: 10, wait: :polynomially_longer)
+
+    limits_concurrency to: 1, key: :screenshots, duration: 2.hours
+
+    queue_as :screenshots
+
+    def perform(user)
+      user.calendar_images.generate
+    end
+  end
+
+  private
+
+  attr_reader :user
+
+  def generate_from_activities
+    calendar_html = render_calendar_html
+
+    capture_html_screenshot(calendar_html)
+  end
+
+  def render_calendar_html
+    activities_amount_per_day = user.calendars.current_year.activities_amount_sum_per_day
+
+    ApplicationController.render("users/signature", locals: { activities_amount_per_day: }, layout: nil)
+  end
+
+  def capture_html_screenshot(html_page)
+    BrowserSession.fetch_page do |page|
+      page.go_to("data:text/html;base64,#{Base64.strict_encode64(html_page)}")
+
+      image = page
+        .screenshot(
+          encoding: :binary,
+          selector: ".signature",
+          format: :png,
+          background_color: Ferrum::RGBA.new(0, 0, 0, 0.0)
+        )
+
+      user.calendar_image.attach(
+        io: StringIO.new(image),
+        filename: "#{user.username}_calendar.png",
+        content_type: "application/png"
+      )
+    end
+  end
+end

app/views/users/signature.html.erb

@@ -3,10 +3,16 @@
   <style type="text/css">
     <%= Rails.application.assets.resolver.read("application.css").html_safe.force_encoding("UTF-8") %>
 
+    html {
+      background-color: transparent !important;
+    }
+    body {
+      background-color: transparent !important;
+    }
     .signature {
-        padding: 0.75em;
-        display: inline-grid;
-        background-color: transparent;
+      padding: 0.75em;
+      display: inline-grid;
+      background-color: transparent !important;
     }
   </style>
 </head>

config/routes.rb

@@ -10,6 +10,10 @@
     resource :signature, only: :show, on: :member
     resources :calendars, only: :show, on: :member, param: "year"
     resources :timelines, only: :show, on: :member, param: "year"
+
+    namespace :images do
+      resource :calendar, on: :member, only: :show
+    end
   end
 
   get "/about", to: "application#about", as: "about"