module ForemanTasks
  module Concerns
    module ActionTriggering

      extend ActiveSupport::Concern

      included do
        after_create :plan_create_action
        after_update :plan_update_action
        after_destroy :plan_destroy_action
      end

      # @override
      def create_action
      end

      # @override
      def update_action
      end

      # @override
      def destroy_action
      end

      def save(*args)
        dynflow_task_wrap(:save) { super(*args) }
      end

      def save!(*args)
        dynflow_task_wrap(:save) { super(*args) }
      end

      def destroy
        dynflow_task_wrap(:destroy) { super }
      end

      def update_attributes(*args)
        dynflow_task_wrap(:save) { super(*args) }
      end

      def update_attributes!(*args)
        dynflow_task_wrap(:save) { super(*args) }
      end

      protected

      def sync_action_flag_reset!
        @dynflow_sync_action = false
      end

      # to make the triggered action synchronous
      def sync_action!
        @dynflow_sync_action = true
      end

      def plan_create_action
        plan_action(create_action, self) if create_action
        return true
      end

      def plan_update_action
        plan_action(update_action, self) if update_action
        return true
      end

      def plan_destroy_action
        plan_action(destroy_action, self) if destroy_action
        return true
      end

      # Perform planning phase of the action tied with the model event.
      # We do it separately from the execution phase, because the transaction
      # of planning phase is expected to be commited when execution occurs. Also
      # we want to be able to rollback the whole db operation when planning fails.
      def plan_action(action_class, *args)
        @execution_plan = ::ForemanTasks.dynflow.world.plan(action_class, *args)
        raise @execution_plan.errors.first if @execution_plan.error?
      end

      # Makes sure the execution plan is executed AFTER the transaction is commited.
      # We can't user after_commit filters because they don't allow to raise
      # exceptions in there, so we would not be able to report that something
      # went wrong when running a sync_task.:
      #
      #   http://guides.rubyonrails.org/v3.2.14/active_record_validations_callbacks.html#transaction-callbacks
      #
      # That's why we need to override save and destroy methods instead.
      # Another reason why one should avoid callbacks for orchestration.
      #
      # Also, it makes sure the save is not run inside other transaction because
      # we would start the execution phase inside this transaction which would lead
      # to unexpected results.
      def dynflow_task_wrap(method)
        return yield if @_dynflow_task_wrapped
        @_dynflow_task_wrapped = true

        action = case method
                 when :save
                   self.new_record? ? create_action : update_action
                 when :destroy
                   destroy_action
                 else
                   raise 'unexpected method'
                 end
        if action
          ensure_not_in_transaction!
          yield.tap do |result|
            execute_planned_action if result
            sync_action_flag_reset!
          end
        else
          yield
        end
      ensure
        @_dynflow_task_wrapped = false
      end

      # we don't want to start executing the task calling to external services
      # when inside some other transaction. Might lead to unexpected results
      def ensure_not_in_transaction!
        if self.class.connection.open_transactions > 0
          raise 'Executing dynflow action inside a transaction is not a good idea'
        end
      end

      # Execute the prepared execution plan after the db transaction was commited
      def execute_planned_action
        if @execution_plan
          run = ::ForemanTasks.dynflow.world.execute(@execution_plan.id)
          if @dynflow_sync_action
            run.wait
            if run.value.error?
              task = ForemanTasks::Task::DynflowTask.find_by_external_id!(@execution_plan.id)
              raise ForemanTasks::TaskError.new(task)
            end
          end
        end
        return true
      end
    end
  end
end