require "ezid-client"
require "resque"

module Ddr
  module Managers
    #
    # PermanentIdManager is responsible for managing the permanent id for an object.
    #
    # @api private
    #
    class PermanentIdManager

      PERMANENT_URL_BASE   = "http://id.library.duke.edu/"
      ASSIGN_EVENT_SUMMARY = "Permanent ID assignment"
      SOFTWARE             = Ezid::Client.version
      FCREPO3_PID          = "fcrepo3.pid"
      FCREPO4_ID           = "fcrepo4.id"

      attr_reader :object

      def initialize(object)
        @object = object
      end

      def assign_later
        Resque.enqueue(AssignmentJob, object.id)
      end

      def assign
        raise Ddr::Models::Error, "Permanent ID already assigned." if object.permanent_id
        ActiveSupport::Notifications.instrument(Ddr::Notifications::UPDATE,
                                                pid: object.id,
                                                software: SOFTWARE,
                                                summary: ASSIGN_EVENT_SUMMARY
                                                ) do |payload|

          assign!
          payload[:detail] = <<-EOS
Permanent ID:  #{object.permanent_id}
Permanent URL: #{object.permanent_url}
EZID Metadata:
#{record.metadata}
          EOS
        end
      end

      # A job class for background execution
      class AssignmentJob
        @queue = :permanent_id

        def self.perform(id)
          object = ActiveFedora::Base.find(id)
          object.permanent_id_manager.assign
        end
      end

      def default_metadata
        { :profile => "dc",
          :export => "no",
          FCREPO4_ID => object.id
        }
      end

      def record
        return @record if @record
        if object.permanent_id
          @record = Ezid::Identifier.find(object.permanent_id.to_s)
        end
      end

      private

        def assign!
          @record = mint
          object.permanent_id = record.id
          object.permanent_url = (PERMANENT_URL_BASE + object.permanent_id)
          object.save!
        end

        # @return [Ezid::Identifier]
        def mint
          ezid = Ezid::Identifier.create(default_metadata)
          ezid.target = default_target_url(ezid.id)
          ezid.save
          ezid
        end

        def default_target_url(id)
          Ddr::Models.permanent_id_target_url_base + id
        end

    end
  end
end