version_resolver.rb

# frozen_string_literal: true

module Contacts
  module Services
    module SlsEvents
      class Importer
        module Consumers
          #
          # Contacts::Services::SlsEvents::Importer::Consumers::VersionResolver
          #
          # Abstracts the cases for resource version management
          # Returns one of: :stale, :update, :confirm, :conflict, :sync

          class VersionResolver
            attr_reader :local_our_version, :local_their_version, :incoming_their_version, :incoming_our_version

            def initialize(local_our_version:, local_their_version:, incoming_their_version:, incoming_our_version:)
              @local_our_version      = local_our_version
              @local_their_version    = local_their_version
              @incoming_their_version = incoming_their_version
              @incoming_our_version   = incoming_our_version
            end

            def call
              return :conflict if conflict?
              return :confirmation if confirmation?
              return :stale if stale?
              return :update if update?
              return :sync if sync?

              raise "Unexpected versioning case happened: #{[local_our_version, local_their_version, incoming_their_version, incoming_our_version].join(',')}"
            end

            private

            def confirmation?
              [
                incoming_their_version,
                incoming_our_version,
                local_our_version,
              ].uniq.length == 1 && local_their_version < incoming_their_version
            end

            def update?
              incoming_their_version > incoming_our_version# && incoming_our_version <= local_our_version
            end

            def conflict?
              update? && incoming_our_version != local_our_version
            end

            def stale?
              incoming_our_version < local_our_version && !update?
            end

            def sync?
              all_fields.uniq.length == 1
            end

            def all_fields
              [
                incoming_their_version,
                incoming_our_version,
                local_our_version,
                local_their_version,
              ]
            end
          end
        end
      end
    end
  end
end


__END__

vr = Contacts::Services::SlsQueue::Importer::Consumers::VersionResolver.new(
  local_our_version: 4,
  local_their_version: 4,
  incoming_their_version: 5,
  incoming_our_version: 4,
)

vr.call