Braindump CQRS

Braindump CQRS.rb

# CLIENT (if RAILS)

class ChangeTreatmentForm
	include ActiveModel::Model
	
	attr_reader :reason, :episode_id, :new_treament_id

	validate :reason, :episode_id, :new_treatment_id present: true

	def to_command
		ChangeTreatmentCommand.new(@new_treatment_id, @episode_id, @reason)
	end
end

# SERVER

class EpisodesController
	def treatment
		form = ChangeTreatmentForm.new(params)
		result = ChangeTreatmentHandler.new(form.to_command).call
		head :ok if result
	end
end

class ChangeTreatmentCommand < Struct.new(:new_treatment_id, :episode_id, :reason)
end

class BaseHandler
	pattr :command

	def initialize(command)
		@command = command
	end

	def call
		authorize @command.to_s
		ActiveRecord::Base.transaction do
			perform
			redis.LPUSH(:commands, @command) # => RAW event store
		end
	end

	protected

	def perform
		raise "IMPLEMENT SOMETHING"
	end
end

class ChangeTreatmentHandler < BaseHandler
	def perform
		episode = Episode.find(command.episode_id)
		episode.complete(command.reason)
		episode.save!

		Episode.create!(
			patient_id: episode.patient_id, 
			treatment_id: command.new_treatment_id
		)
	end
end

class Episode < ActiveRecord::Base
	def complete(reason)
		self.ended_at = Time.current
		self.reason = reason

		# Synchronous, part of the domain operation
		Planning.clear_episode(self.id)

		# Asynchronous, part of the domain operation
		ClearPlanningJob.new(self.id).perform_later

		# Synchronous / Asynchronous (up to the handler), NOT part of the domain operation
		Whisper.broadcast(:episode_completed, self.id) 
	end
end

Whisper.subscribe(:episode_completed, EpisodeCompletedHandler)

class EpisodeCompletedHandler
	def call
		# Mail some doctor
		# Print something ...
	end
end