Add timeline read markers API (#11762)

Fix #4093

app/controllers/api/v1/markers_controller.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+class Api::V1::MarkersController < Api::BaseController
+  before_action -> { doorkeeper_authorize! :read, :'read:statuses' }, only: [:index]
+  before_action -> { doorkeeper_authorize! :write, :'write:statuses' }, except: [:index]
+
+  before_action :require_user!
+
+  def index
+    @markers = current_user.markers.where(timeline: Array(params[:timeline])).each_with_object({}) { |marker, h| h[marker.timeline] = marker }
+    render json: serialize_map(@markers)
+  end
+
+  def create
+    Marker.transaction do
+      @markers = {}
+
+      resource_params.each_pair do |timeline, timeline_params|
+        @markers[timeline] = current_user.markers.find_or_initialize_by(timeline: timeline)
+        @markers[timeline].update!(timeline_params)
+      end
+    end
+
+    render json: serialize_map(@markers)
+  rescue ActiveRecord::StaleObjectError
+    render json: { error: 'Conflict during update, please try again' }, status: 409
+  end
+
+  private
+
+  def serialize_map(map)
+    serialized = {}
+
+    map.each_pair do |key, value|
+      serialized[key] = ActiveModelSerializers::SerializableResource.new(value, serializer: REST::MarkerSerializer).as_json
+    end
+
+    Oj.dump(serialized)
+  end
+
+  def resource_params
+    params.slice(*Marker::TIMELINES).permit(*Marker::TIMELINES.map { |timeline| { timeline.to_sym => [:last_read_id] } })
+  end
+end