api feature: add avatar url to user endpoint

app/helpers/users_helper.rb

@@ -1,20 +1,44 @@
 module UsersHelper
-  
+
   # see also: /config/initializers/gravatar_image_tag.rb
-  
+
   def avatar(user)
     case user.avatar_provider
     when 'gravatar'
       if user.avatar.nil? or user.avatar.empty? then
         content_tag :div, nil, class: [ 'avatar-missing' ]
-      else 
+      else
         gravatar_image_tag user.avatar, class: user.active? ? '' : 'disabled'
       end
     when 'webfinger'
       webfinger_activitypub_image_tag user.avatar
     end
   end
 
+  def get_avatar_url(user)
+    case user.avatar_provider
+    when 'gravatar'
+      if user.avatar.nil? or user.avatar.empty? then
+        return nil
+      end
+
+      id = Digest::MD5.hexdigest(user.avatar)
+      return "https://secure.gravatar.com/avatar/#{id}"
+    when 'webfinger'
+      identifier = user.avatar
+      avatar_url = Rails.cache.fetch("fetch_avatar_url_from_webfinger_or_activitypub #{identifier}", expires_in: 1.day) do
+        fetch_avatar_url_from_webfinger_or_activitypub identifier
+      end
+
+      if not avatar_url
+        return nil
+      end
+
+      return avatar_url
+    end
+
+  end
+
   def redirect_path(user)
     return users_path + '/#' + user.initial
   end

app/models/user.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+include UsersHelper
+
 class User < ApplicationRecord
   validates :name, presence: true
   validates :barcode, uniqueness: { conditions: -> { where.not(barcode: nil) } }
@@ -15,7 +17,7 @@ class User < ApplicationRecord
       user.barcode = nil
     end
   end
-  
+
 
   after_save do |user|
     Audit.create! difference: user.balance - user.balance_before_last_save, drink: @purchased_drink, user: user.audit? ? user : nil
@@ -58,7 +60,13 @@ def email
     end
   end
 
+  def avatar_url
+    @url = get_avatar_url(self)
+    @url
+  end
+
+
   def as_json(options={})
-    super(except: [ :avatar_provider, :avatar ], methods: :email)
+    super(except: [ :avatar_provider, :avatar ], methods: [ :email, :avatar_url ])
   end
 end