fix add items to collection method

app/controllers/v1/collections_controller.rb

@@ -43,7 +43,7 @@ class V1::CollectionsController < ApplicationController
   # PUT/PATCH /v1/users/1.json
   def update
     if @collection.update(collection_params)
-      @collection.add_items(extra_params[:items])
+      collection_associations(@collection)
       render json: @collection, status: :ok
     else
       render json: @collection.errors, status: :unprocessable_entity
@@ -97,7 +97,7 @@ class V1::CollectionsController < ApplicationController
 
   def extra_params
     return {} if params[:collection].nil?
-    params[:collection].permit(subjects: [], educational_stages: [], items: [:id, :name, :type], tags: [:name])
+    params[:collection].permit(subjects: [], educational_stages: [], items: [:id, :type, :position], tags: [:name])
   end
 
   def collection_associations(collection)

app/models/collection.rb

@@ -35,7 +35,7 @@ class Collection < ApplicationRecord
   include Highlights
   include Complainable
 
-  has_many :collection_items, as: :collectionable, dependent: :destroy
+  has_many :collection_items, -> { order("position ASC") }, as: :collectionable, dependent: :destroy
   has_many :collections, through: :collection_items, source: :collectionable, source_type: 'Collection'
   has_many :learning_objects, through: :collection_items, source: :collectionable, source_type: 'LearningObject'
   has_many :collection_items
@@ -84,14 +84,10 @@ class Collection < ApplicationRecord
   end
 
   def add_items(items)
-    collection_items = items.map do |item|
-      CollectionItem.new(
-        collection: self,
-        collectionable: item[:type].constantize.find(item[:id]),
-        order: item[:order]
-      )
+    items.each do |item|
+      col_item = CollectionItem.where(collection: self, collectionable_id: item[:id], collectionable_type: item[:type]).first_or_create
+      col_item.set_list_position(item[:position]) unless item[:position].nil?
     end
-    CollectionItem.import collection_items, on_duplicate_key_update: { conflict_target: [:collection_id, :collectionable_id, :collectionable_type], columns: [:order] }
   end
 
   def delete_items(items)

app/models/collection_item.rb

@@ -19,7 +19,7 @@ class CollectionItem < ApplicationRecord
   belongs_to :collectionable, polymorphic: true
 
   validates :collection, :collectionable, presence: true
-  validates :order, uniqueness: true, allow_blank: true
+  acts_as_list scope: :collection
 
   def recipient
     collection