FEATURE: Publish read state on group messages. (Originally introduced in #7989) (#8025)

* Revert "Revert "FEATURE: Publish read state on group messages. (#7989) [Undo revert] (#8024)""

This reverts commit 36425eb9f04cfac7201632d648050cb43a035bc1.

* Fix: Show who read only if the attribute is enabled

* PERF: Precalculate the last post  readed by a group member

* Use book-reader icon instear of far-eye

* FIX: update topic groups correctly

* DEV: Tidy up read indicator update on write

spec/models/topic_group_spec.rb

@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe TopicGroup do
+  describe '#update_last_read' do
+    fab!(:group) { Fabricate(:group) }
+    fab!(:user) { Fabricate(:user) }
+
+    before do
+      @topic = Fabricate(:private_message_topic, allowed_groups: [group])
+      group.add(user)
+    end
+
+    it 'does nothing if the user is not a member of an allowed group' do
+      another_user = Fabricate(:user)
+
+      described_class.update_last_read(another_user, @topic.id, @topic.highest_post_number)
+      created_topic_group = described_class.where(topic: @topic, group: group).exists?
+
+      expect(created_topic_group).to eq(false)
+    end
+
+    it 'creates a new record if the user is a member of an allowed group' do
+      described_class.update_last_read(user, @topic.id, @topic.highest_post_number)
+      created_topic_group = described_class.find_by(topic: @topic, group: group)
+
+      expect(created_topic_group.last_read_post_number).to eq @topic.highest_post_number
+    end
+
+    it 'does nothing if the topic does not have allowed groups' do
+      @topic.update!(allowed_groups: [])
+
+      described_class.update_last_read(user, @topic.id, @topic.highest_post_number)
+      created_topic_group = described_class.where(topic: @topic, group: group).exists?
+
+      expect(created_topic_group).to eq(false)
+    end
+
+    it 'updates an existing record with a higher post number' do
+      described_class.create!(topic: @topic, group: group, last_read_post_number: @topic.highest_post_number - 1)
+
+      described_class.update_last_read(user, @topic.id, @topic.highest_post_number)
+      created_topic_group = described_class.find_by(topic: @topic, group: group)
+
+      expect(created_topic_group.last_read_post_number).to eq @topic.highest_post_number
+    end
+
+    it 'does nothing if the user read post number is lower than the current one' do
+      highest_read_number = @topic.highest_post_number + 1
+      described_class.create!(topic: @topic, group: group, last_read_post_number: highest_read_number)
+
+      described_class.update_last_read(user, @topic.id, @topic.highest_post_number)
+      created_topic_group = described_class.find_by(topic: @topic, group: group)
+
+      expect(created_topic_group.last_read_post_number).to eq highest_read_number
+    end
+
+    it 'creates a new record if the list of allowed groups has changed' do
+      another_allowed_group = Fabricate(:group)
+      another_allowed_group.add(user)
+      @topic.allowed_groups << another_allowed_group
+      described_class.create!(topic: @topic, group: group, last_read_post_number: @topic.highest_post_number)
+
+      described_class.update_last_read(user, @topic.id, @topic.highest_post_number)
+      created_topic_group = described_class.find_by(topic: @topic, group: another_allowed_group)
+
+      expect(created_topic_group.last_read_post_number).to eq @topic.highest_post_number
+    end
+
+    it 'Only updates the record that shares the same topic_id' do
+      new_post_number = 100
+      topic2 = Fabricate(:private_message_topic, allowed_groups: [group], topic_allowed_users: [])
+      described_class.create!(topic: @topic, group: group, last_read_post_number: @topic.highest_post_number)
+      described_class.create!(topic: topic2, group: group, last_read_post_number: topic2.highest_post_number)
+
+      described_class.update_last_read(user, @topic.id, new_post_number)
+      created_topic_group = described_class.find_by(topic: @topic, group: group)
+      created_topic_group2 = described_class.find_by(topic: topic2, group: group)
+
+      expect(created_topic_group.last_read_post_number).to eq new_post_number
+      expect(created_topic_group2.last_read_post_number).to eq topic2.highest_post_number
+    end
+  end
+end