Post Queue model to enqueue creation of posts

app/models/queued_post.rb

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+class QueuedPost < ActiveRecord::Base
+
+  class InvalidStateTransition < StandardError; end;
+
+  serialize :post_options, JSON
+
+  belongs_to :user
+  belongs_to :topic
+  belongs_to :approved_by, class_name: "User"
+  belongs_to :rejected_by, class_name: "User"
+
+  def self.attributes_by_queue
+    @attributes_by_queue ||= {
+      base: [:archetype,
+             :via_email,
+             :raw_email,
+             :auto_track,
+             :custom_fields,
+             :cooking_options,
+             :cook_method,
+             :image_sizes],
+      new_post: [:reply_to_post_number],
+      new_topic: [:title, :category, :meta_data, :archetype],
+    }
+  end
+
+  def self.states
+    @states ||= Enum.new(:new, :approved, :rejected)
+  end
+
+  def reject!(rejected_by)
+    change_to!(:rejected, rejected_by)
+  end
+
+  def create_options
+    opts = {raw: raw}
+    post_attributes.each {|a| opts[a] = post_options[a.to_s] }
+
+    opts[:topic_id] = topic_id if topic_id
+    opts
+  end
+
+  def approve!(approved_by)
+    created_post = nil
+    QueuedPost.transaction do
+      change_to!(:approved, approved_by)
+
+      creator = PostCreator.new(user, create_options)
+      created_post = creator.create
+    end
+    created_post
+  end
+
+  private
+    def post_attributes
+      [QueuedPost.attributes_by_queue[:base], QueuedPost.attributes_by_queue[queue.to_sym]].flatten.compact
+    end
+
+    def change_to!(state, changed_by)
+      state_val = QueuedPost.states[state]
+
+      updates = { state: state_val,
+                  "#{state}_by_id" => changed_by.id,
+                  "#{state}_at" => Time.now }
+
+      # We use an update with `row_count` trick here to avoid stampeding requests to
+      # update the same row simultaneously. Only one state change should go through and
+      # we can use the DB to enforce this
+      row_count = QueuedPost.where('id = ? AND state <> ?', id, state_val).update_all(updates)
+      raise InvalidStateTransition.new if row_count == 0
+
+      # Update the record in memory too, and clear the dirty flag
+      updates.each {|k, v| send("#{k}=", v) }
+      changes_applied
+    end
+
+end

db/migrate/20150325160959_create_queued_posts.rb

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+class CreateQueuedPosts < ActiveRecord::Migration
+  def change
+    create_table :queued_posts do |t|
+      t.string     :queue, null: false
+      t.integer    :state, null: false
+      t.integer    :user_id, null: false
+      t.text       :raw, null: false
+      t.text       :post_options, null: false
+      t.integer    :topic_id
+      t.integer    :approved_by_id
+      t.timestamp  :approved_at
+      t.integer    :rejected_by_id
+      t.timestamp  :rejected_at
+      t.timestamps
+    end
+
+    add_index :queued_posts, [:queue, :state, :created_at], name: 'by_queue_status'
+    add_index :queued_posts, [:topic, :queue, :state, :created_at], name: 'by_queue_status_topic'
+  end
+end

spec/models/queued_post_spec.rb

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+require 'spec_helper'
+require_dependency 'queued_post'
+
+describe QueuedPost do
+
+  context "creating a post" do
+    let(:topic) { Fabricate(:topic) }
+    let(:user) { Fabricate(:user) }
+    let(:admin) { Fabricate(:admin) }
+    let(:qp) { QueuedPost.create(queue: 'new_post',
+                                 state: QueuedPost.states[:new],
+                                 user_id: user.id,
+                                 topic_id: topic.id,
+                                 raw: 'This post should be queued up',
+                                 post_options: {
+                                   reply_to_post_number: 1,
+                                   via_email: true,
+                                   raw_email: 'store_me',
+                                   auto_track: true,
+                                   custom_fields: { hello: 'world' },
+                                   cooking_options: { cat: 'hat' },
+                                   cook_method: 'regular',
+                                   not_create_option: true,
+                                   image_sizes: {"http://foo.bar/image.png" => {"width" => 0, "height" => 222}}
+                                 }) }
+
+    it "returns the appropriate options for posting" do
+      create_options = qp.create_options
+
+      expect(create_options[:topic_id]).to eq(topic.id)
+      expect(create_options[:raw]).to eq('This post should be queued up')
+      expect(create_options[:reply_to_post_number]).to eq(1)
+      expect(create_options[:via_email]).to eq(true)
+      expect(create_options[:raw_email]).to eq('store_me')
+      expect(create_options[:auto_track]).to eq(true)
+      expect(create_options[:custom_fields]).to eq('hello' => 'world')
+      expect(create_options[:cooking_options]).to eq('cat' => 'hat')
+      expect(create_options[:cook_method]).to eq('regular')
+      expect(create_options[:not_create_option]).to eq(nil)
+      expect(create_options[:image_sizes]).to eq("http://foo.bar/image.png" => {"width" => 0, "height" => 222})
+    end
+
+    it "follows the correct workflow for approval" do
+      post = qp.approve!(admin)
+
+      # Creates the post with the attributes
+      expect(post).to be_present
+      expect(post).to be_valid
+      expect(post.topic).to eq(topic)
+
+      # Updates the QP record
+      expect(qp.approved_by).to eq(admin)
+      expect(qp.state).to eq(QueuedPost.states[:approved])
+      expect(qp.approved_at).to be_present
+
+      # We can't approve twice
+      expect(-> { qp.approve!(admin) }).to raise_error(QueuedPost::InvalidStateTransition)
+
+    end
+
+    it "follows the correct workflow for rejection" do
+      qp.reject!(admin)
+
+      # Updates the QP record
+      expect(qp.rejected_by).to eq(admin)
+      expect(qp.state).to eq(QueuedPost.states[:rejected])
+      expect(qp.rejected_at).to be_present
+
+      # We can't reject twice
+      expect(-> { qp.reject!(admin) }).to raise_error(QueuedPost::InvalidStateTransition)
+    end
+  end
+
+  context "creating a topic" do
+    let(:user) { Fabricate(:user) }
+    let(:admin) { Fabricate(:admin) }
+    let!(:category) { Fabricate(:category) }
+
+    let(:qp) { QueuedPost.create(queue: 'new_topic',
+                                 state: QueuedPost.states[:new],
+                                 user_id: user.id,
+                                 raw: 'This post should be queued up',
+                                 post_options: {
+                                   title: 'This is the topic title to queue up',
+                                   archetype: 'regular',
+                                   category: category.id,
+                                   meta_data: {evil: 'trout'}
+                                 }) }
+
+
+    it "returns the appropriate options for creating a topic" do
+      create_options = qp.create_options
+
+      expect(create_options[:category]).to eq(category.id)
+      expect(create_options[:archetype]).to eq('regular')
+      expect(create_options[:meta_data]).to eq('evil' => 'trout')
+    end
+
+    it "creates the post and topic" do
+      topic_count, post_count = Topic.count, Post.count
+      post = qp.approve!(admin)
+
+      expect(Topic.count).to eq(topic_count + 1)
+      expect(Post.count).to eq(post_count + 1)
+
+      expect(post).to be_present
+      expect(post).to be_valid
+
+      topic = post.topic
+      expect(topic).to be_present
+      expect(topic.category).to eq(category)
+    end
+
+    it "doesn't create the post and topic" do
+      topic_count, post_count = Topic.count, Post.count
+
+      qp.reject!(admin)
+
+      expect(Topic.count).to eq(topic_count)
+      expect(Post.count).to eq(post_count)
+    end
+  end
+
+end