pmex

Purpose of this application is a case stady of implementing DSL for process manager in Elixir.
EventsStream, subscription to EventsStream and pulling mechanisms implemented solelly as a mockup in order to drive process manager.

pmex starting with EventsStream and OrderingProcess already running and subscribed.

Example of process definition

defmodule OrderingProcess do
    use ProcessManager, initial_step: :start

    ######################################## Steps definitions ###################################

    defstep start do
        defevent order_started(%{customer: customer_id, order: order_id}) do
            open_shopping_cart(customer_id, order_id)
            go product_selection
        end
    end

    defstep product_selection do
        defevent product_selected(%{order: order_id, product: product_id}) do
            add_to_cart(order_id, product_id)
            go product_selection
        end

        defevent product_removed(%{order: order_id, product: product_id}) do
            remove_from_cart(order_id, product_id)
            go product_selection
        end

        defevent selection_completed(%{order: order_id}) do
            request_payment(order_id)
            go await_payment
        end 
    end

    defstep await_payment do
        defevent payment_done(%{order: order_id}) do
            complete_order(order_id)
            go order_confirmation
        end

        defevent payment_failed(%{order: order_id}) do
            cancel_order(order_id)
            go cancel_confirmation
        end
    end

    defstep order_confirmation do
        defevent order_closed(%{customer: customer_id, track_id: track}) do
            send_email(customer_id, track)
            finish
        end 
    end

    defstep cancel_confirmation do
        defevent order_canceled(%{customer: customer_id, order: order_id}) do
            send_cancelation_email(customer_id, order_id)
            finish
        end 
    end

    ############################## Commands implementations #######################################

    def open_shopping_cart(customer_id, order_id) do
        Logger.info "Command exec: open_shopping_cart: customer_id=#{customer_id}, order_id=#{order_id}"
    end

    def add_to_cart(order_id, product_id) do
        Logger.info "Command exec: add_to_cart: order_id=#{order_id}, product_id=#{product_id}"
    end

    def remove_from_cart(order_id, product_id) do
        Logger.info "Command exec: remove_from_cart: order_id=#{order_id}, product_id=#{product_id}"
    end

    def request_payment(order_id) do
        Logger.info "Command exec: request_payment: order_id=#{order_id}"
    end

    def complete_order(order_id) do
        Logger.info "Command exec: complete_order: order_id=#{order_id}"
    end

    def cancel_order(order_id) do
        Logger.info "Command exec: cancel_order: order_id=#{order_id}"
    end

    def send_email(customer_id, track) do
        Logger.info "Command exec: send_email: customer_id=#{customer_id} track=#{track}"
    end

    def send_cancelation_email(customer_id, order_id) do
        Logger.info "Command exec: send_cancelation_email: customer_id=#{customer_id} order_id=#{order_id}"
    end

end

Step definition

defstep start do #step name
        defevent order_started(%{customer: customer_id, order: order_id}) do #event name and its payload paremeters
            open_shopping_cart(customer_id, order_id) #command that should be sent when event received
            go product_selection #next step
        end
end

1. Step can have several events.
2. Each event can define different next step.
3. Next step can be same or other step.

Command functions should be implemented in the module

def open_shopping_cart(customer_id, order_id) do
        Logger.info "Command exec: open_shopping_cart: customer_id=#{customer_id}, order_id=#{order_id}"
end

In order to proceed with the ordering process, submit following events to EventsStream:

Case 1

EventsStream.put({:order_started, %{customer: 123, order: 778899}})
EventsStream.put({:product_selected, %{order: 778899, product: 67890000}})
EventsStream.put({:product_removed, %{order: 778899, product: 67890000}})
EventsStream.put({:product_selected, %{order: 778899, product: 67890001}})
EventsStream.put({:product_selected, %{order: 778899, product: 67890002}})
EventsStream.put({:selection_completed, %{order: 778899}})
EventsStream.put({:payment_done, %{order: 778899}})
EventsStream.put({:order_closed, %{customer: 123, track_id: "EX32746932878CH"}})

Case 2

EventsStream.put({:order_started, %{customer: 123, order: 778899}})
EventsStream.put({:product_selected, %{order: 778899, product: 67890000}})
EventsStream.put({:product_removed, %{order: 778899, product: 67890000}})
EventsStream.put({:product_selected, %{order: 778899, product: 67890001}})
EventsStream.put({:product_selected, %{order: 778899, product: 67890002}})
EventsStream.put({:selection_completed, %{order: 778899}})
EventsStream.put({:payment_failed, %{order: 778899}})
EventsStream.put({:order_canceled, %{customer: 123, order: 778899}})