Add discourse-presence as a core plugin (#5137)

* Add discourse-presence as a core plugin

* Default enabled

plugins/discourse-presence/spec/presence_manager_spec.rb

@@ -0,0 +1,64 @@
+require 'rails_helper'
+
+describe ::Presence::PresenceManager do
+
+  let(:user1) { Fabricate(:user) }
+  let(:user2) { Fabricate(:user) }
+  let(:user3) { Fabricate(:user) }
+  let(:manager) { ::Presence::PresenceManager }
+
+  after(:each) do
+    $redis.del('presence:post:22')
+    $redis.del('presence:post:11')
+  end
+
+  it 'adds, removes and lists users correctly' do
+    expect(manager.get_users('post', 22).count).to eq(0)
+
+    expect(manager.add('post', 22, user1.id)).to be true
+    expect(manager.add('post', 22, user2.id)).to be true
+    expect(manager.add('post', 11, user3.id)).to be true
+
+    expect(manager.get_users('post', 22).count).to eq(2)
+    expect(manager.get_users('post', 11).count).to eq(1)
+
+    expect(manager.get_users('post', 22)).to contain_exactly(user1, user2)
+    expect(manager.get_users('post', 11)).to contain_exactly(user3)
+
+    expect(manager.remove('post', 22, user1.id)).to be true
+    expect(manager.get_users('post', 22).count).to eq(1)
+    expect(manager.get_users('post', 22)).to contain_exactly(user2)
+  end
+
+  it 'publishes correctly' do
+    expect(manager.get_users('post', 22).count).to eq(0)
+
+    manager.add('post', 22, user1.id)
+    manager.add('post', 22, user2.id)
+
+    messages = MessageBus.track_publish do
+      manager.publish('post', 22)
+    end
+
+    expect(messages.count).to eq (1)
+    message = messages.first
+
+    expect(message.channel).to eq('/presence/post/22')
+
+    expect(message.data["users"].map { |u| u[:id] }).to contain_exactly(user1.id, user2.id)
+  end
+
+  it 'cleans up correctly' do
+    freeze_time Time.zone.now do
+      expect(manager.add('post', 22, user1.id)).to be true
+      expect(manager.cleanup('post', 22)).to be false # Nothing to cleanup
+      expect(manager.get_users('post', 22).count).to eq(1)
+    end
+
+    # Anything older than 20 seconds should be cleaned up
+    freeze_time 30.seconds.from_now do
+      expect(manager.cleanup('post', 22)).to be true
+      expect(manager.get_users('post', 22).count).to eq(0)
+    end
+  end
+end