RailsEventStore/cqrs-es-sample-with-res

module Processes
  class ReleasePaymentProcess
    def initialize(event_store, command_bus)
      @event_store = event_store
      @command_bus = command_bus
    end

    def call(event)
      state = build_state(event)
      release_payment(state) if state.release?
    end

    private

    def release_payment(state)
      command_bus.call(Payments::ReleasePayment.new(order_id: state.order_id))
    end

    attr_reader :command_bus, :event_store

    def build_state(event)
      stream_name = "PaymentProcess$#{event.data.fetch(:order_id)}"
      past_events = event_store.read.stream(stream_name).to_a
      last_stored = past_events.size - 1
      event_store.link(event.event_id, stream_name: stream_name, expected_version: last_stored)
      ProcessState.new.tap do |state|
        past_events.each { |ev| state.call(ev) }
        state.call(event)
      end
    rescue RubyEventStore::WrongExpectedEventVersion
      retry
    end

    class ProcessState
      def initialize
        @order = :draft
        @payment = :none
      end

      attr_reader :order_id

      def call(event)
        case event
        when Payments::PaymentAuthorized
          @payment = :authorized
        when Payments::PaymentReleased
          @payment = :released
        when Ordering::OrderPlaced
          @order = :placed
          @order_id = event.data.fetch(:order_id)
        when Ordering::OrderExpired
          @order = :expired
        when Ordering::OrderConfirmed
          @order = :confirmed
        end
      end

      def release?
        @payment.eql?(:authorized) && @order.eql?(:expired)
      end
    end
  end
end