Add GET /api/v1/notices and DELETE /api/v1/notices/:id

app/controllers/api/v1/notices_controller.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+class Api::V1::NoticesController < Api::BaseController
+  before_action -> { doorkeeper_authorize! :write, :'write:accounts' }, only: :destroy
+  before_action :require_user!
+  before_action :set_notices, only: :index
+  before_action :set_notice, except: :index
+
+  def index
+    render json: @notices, each_serializer: REST::NoticeSerializer
+  end
+
+  def destroy
+    @notice.dismiss_for_user!(current_user)
+    render_empty
+  end
+
+  private
+
+  def set_notices
+    @notices = [Notice.first_unseen(current_user)].compact
+  end
+
+  def set_notice
+    @notice = Notice.find(params[:id])
+  end
+end

app/models/notice.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+class Notice < ActiveModelSerializers::Model
+  attributes :id, :icon, :title, :message, :actions
+
+  # Notices a user has seen are stored as a bitmap in
+  # `users.seen_notifications`.
+  NOTICE_BIT_MAP = {}.freeze
+
+  def dismiss_for_user!(user)
+    user.update!(seen_notices: (user.seen_notices || 0) | NOTICE_BIT_MAP[id])
+  end
+
+  class Action < ActiveModelSerializers::Model
+    attributes :label, :url
+  end
+
+  class << self
+    include RoutingHelper
+
+    def first_unseen(user)
+      notice_key = NOTICE_BIT_MAP.find { |_, bit| ((user.seen_notices || 0) & bit).zero? }&.first
+
+      send("#{notice_key}_notice") if notice_key.present?
+    end
+
+    def find(key)
+      throw ActiveRecord::RecordNotFound unless NOTICE_BIT_MAP.key?(key.to_sym)
+
+      send("#{key}_notice")
+    end
+  end
+end

app/serializers/rest/notice_serializer.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class REST::NoticeSerializer < ActiveModel::Serializer
+  class ActionSerializer < ActiveModel::Serializer
+    attributes :label, :url
+  end
+
+  attributes :id, :icon, :title, :message
+
+  has_many :actions, serializer: ActionSerializer
+end

config/routes/api.rb

@@ -61,6 +61,8 @@ namespace :api, format: false do
       end
     end
 
+    resources :notices, only: [:index, :destroy]
+
     # namespace :crypto do
     #   resources :deliveries, only: :create