DEV: Chat service object initial implementation (#19814)

This is a combined work of Martin Brennan, Loïc Guitaut, and Joffrey Jaffeux.

---

This commit implements a base service object when working in chat. The documentation is available at https://discourse.github.io/discourse/chat/backend/Chat/Service.html

Generating documentation has been made as part of this commit with a bigger goal in mind of generally making it easier to dive into the chat project.

Working with services generally involves 3 parts:

- The service object itself, which is a series of steps where few of them are specialized (model, transaction, policy)

```ruby
class UpdateAge
  include Chat::Service::Base

  model :user, :fetch_user
  policy :can_see_user
  contract
  step :update_age

  class Contract
    attribute :age, :integer
  end

  def fetch_user(user_id:, **)
    User.find_by(id: user_id)
  end

  def can_see_user(guardian:, **)
    guardian.can_see_user(user)
  end

  def update_age(age:, **)
    user.update!(age: age)
  end
end
```

- The `with_service` controller helper, handling success and failure of the service within a service and making easy to return proper response to it from the controller

```ruby
def update
  with_service(UpdateAge) do
    on_success { render_serialized(result.user, BasicUserSerializer, root: "user") }
  end
end
```

- Rspec matchers and steps inspector, improving the dev experience while creating specs for a service

```ruby
RSpec.describe(UpdateAge) do
  subject(:result) do
    described_class.call(guardian: guardian, user_id: user.id, age: age)
  end

  fab!(:user) { Fabricate(:user) }
  fab!(:current_user) { Fabricate(:admin) }

  let(:guardian) { Guardian.new(current_user) }
  let(:age) { 1 }

   it { expect(user.reload.age).to eq(age) }
end
```

Note in case of unexpected failure in your spec, the output will give all the relevant information:

```
  1) UpdateAge when no channel_id is given is expected to fail to find a model named 'user'
     Failure/Error: it { is_expected.to fail_to_find_a_model(:user) }

       Expected model 'foo' (key: 'result.model.user') was not found in the result object.

       [1/4] [model] 'user' ❌
       [2/4] [policy] 'can_see_user'
       [3/4] [contract] 'default'
       [4/4] [step] 'update_age'

       /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/update_age.rb:32:in `fetch_user': missing keyword: :user_id (ArgumentError)
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:202:in `instance_exec'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:202:in `call'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:219:in `call'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:417:in `block in run!'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:417:in `each'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:417:in `run!'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:411:in `run'
       	from <internal:kernel>:90:in `tap'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/app/services/base.rb:302:in `call'
       	from /Users/joffreyjaffeux/Code/pr-discourse/plugins/chat/spec/services/update_age_spec.rb:15:in `block (3 levels) in <main>'
```

plugins/chat/app/controllers/api/chat_channels_controller.rb

@@ -29,37 +29,9 @@ class Chat::Api::ChatChannelsController < Chat::Api
   end
 
   def destroy
-    confirmation = params.require(:channel).require(:name_confirmation)&.downcase
-    guardian.ensure_can_delete_chat_channel!
-
-    if channel_from_params.title(current_user).downcase != confirmation
-      raise Discourse::InvalidParameters.new(:name_confirmation)
+    with_service Chat::Service::TrashChannel do
+      on_model_not_found(:channel) { raise ActiveRecord::RecordNotFound }
     end
-
-    begin
-      ChatChannel.transaction do
-        channel_from_params.update!(
-          slug:
-            "#{Time.now.strftime("%Y%m%d-%H%M")}-#{channel_from_params.slug}-deleted".truncate(
-              SiteSetting.max_topic_title_length,
-              omission: "",
-            ),
-        )
-        channel_from_params.trash!(current_user)
-        StaffActionLogger.new(current_user).log_custom(
-          "chat_channel_delete",
-          {
-            chat_channel_id: channel_from_params.id,
-            chat_channel_name: channel_from_params.title(current_user),
-          },
-        )
-      end
-    rescue ActiveRecord::Rollback
-      return render_json_error(I18n.t("chat.errors.delete_channel_failed"))
-    end
-
-    Jobs.enqueue(:chat_channel_delete, { chat_channel_id: channel_from_params.id })
-    render json: success_json
   end
 
   def create
@@ -118,37 +90,25 @@ class Chat::Api::ChatChannelsController < Chat::Api
   end
 
   def update
-    guardian.ensure_can_edit_chat_channel!
-
-    if channel_from_params.direct_message_channel?
-      raise Discourse::InvalidParameters.new(
-              I18n.t("chat.errors.cant_update_direct_message_channel"),
-            )
-    end
-
     params_to_edit = editable_params(params, channel_from_params)
     params_to_edit.each { |k, v| params_to_edit[k] = nil if params_to_edit[k].blank? }
-
     if ActiveRecord::Type::Boolean.new.deserialize(params_to_edit[:auto_join_users])
       auto_join_limiter(channel_from_params).performed!
     end
 
-    channel_from_params.update!(params_to_edit)
-
-    ChatPublisher.publish_chat_channel_edit(channel_from_params, current_user)
-
-    if channel_from_params.category_channel? && channel_from_params.auto_join_users
-      Chat::ChatChannelMembershipManager.new(
-        channel_from_params,
-      ).enforce_automatic_channel_memberships
+    with_service(Chat::Service::UpdateChannel, **params_to_edit) do
+      on_success do
+        render_serialized(
+          result.channel,
+          ChatChannelSerializer,
+          root: "channel",
+          membership: result.channel.membership_for(current_user),
+        )
+      end
+      on_model_not_found(:channel) { raise ActiveRecord::RecordNotFound }
+      on_failed_policy(:check_channel_permission) { raise Discourse::InvalidAccess }
+      on_failed_policy(:no_direct_message_channel) { raise Discourse::InvalidAccess }
     end
-
-    render_serialized(
-      channel_from_params,
-      ChatChannelSerializer,
-      root: "channel",
-      membership: channel_from_params.membership_for(current_user),
-    )
   end
 
   private

plugins/chat/app/controllers/api/chat_channels_status_controller.rb

@@ -2,17 +2,10 @@
 
 class Chat::Api::ChatChannelsStatusController < Chat::Api::ChatChannelsController
   def update
-    status = params.require(:status)
-
-    # we only want to use this endpoint for open/closed status changes,
-    # the others are more "special" and are handled by the archive endpoint
-    if !ChatChannel.statuses.keys.include?(status) || status == "read_only" || status == "archive"
-      raise Discourse::InvalidParameters
+    with_service(Chat::Service::UpdateChannelStatus) do
+      on_success { render_serialized(result.channel, ChatChannelSerializer, root: "channel") }
+      on_model_not_found(:channel) { raise ActiveRecord::RecordNotFound }
+      on_failed_policy(:check_channel_permission) { raise Discourse::InvalidAccess }
     end
-
-    guardian.ensure_can_change_channel_status!(channel_from_params, status.to_sym)
-    channel_from_params.public_send("#{status}!", current_user)
-
-    render_serialized(channel_from_params, ChatChannelSerializer, root: "channel")
   end
 end