# Copyright 2014-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
#     http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.

require_relative 'handle_error_activities'
require_relative 'custom_exceptions'

# HandleErrorWorkflow class defines a workflow for the handle_error 
# recipe. This recipe shows how to handle errors encountered during workflow
# execution.
class HandleErrorWorkflow
  extend AWS::Flow::Workflows

  # Use the workflow method to define workflow entry point.
  workflow :handle_error_workflow do
    {
      version: "1.0",
      task_list: "handle_error_workflow",
      execution_start_to_close_timeout: 120,
    }
  end

  # Create an activity client using the activity_client method to schedule
  # activities
  activity_client(:client){ { from_class: "HandleErrorActivities" } }

  # This is the entry point for the workflow
  def handle_error_workflow

    # This future will be set if an exception is encountered
    ex = Future.new

    resource_id = client.allocate_resource

    # If your activities or workflows are asynchronous, (i.e. scheduled using 
    # send_async), you must use error_handler, which is modeled after the 
    # standard ruby begin/rescue/ensure, for error handling.
    error_handler do |t|
      t.begin do
        # Use the activity client to schedule the activity asynchronously.
        client.send_async(:use_resource, resource_id)
      end
      t.rescue Exception do |e|
        # Set the future so that in the ensure step, we can call the
        # handle_exception method.
        ex.set(e)
      end
      t.ensure do
        # If the ex future was set, we call the handle_exception method with the
        # exception and the resource_id
        handle_exception(ex.get, resource_id) if ex.set?
      end
      end
  end

  # Helper method that will handle exceptions for us
  def handle_exception(e, resource_id)
    if e.cause.instance_of? ResourceNoResponseException
      # If the exception is of type ResourceNoResponseException, run the
      # activity to report this as a bad resource.
      client.report_resource(resource_id) 
    elsif e.cause.instance_of? ResourceNotAvailableException
      # If the exception is of type ResourceNotAvailableException, run the
      # activity to refresh the resource catalog
      client.refresh_catalogue(resource_id)
    else
      # If the exception is not one of the handled types, then throw it
      # again to be handled up the chain.
      throw e
    end

  end
end