# Copyright (C) 2012-2024 Zammad Foundation, https://zammad-foundation.org/

class Sequencer::Unit::Import::Common::Model::Lookup::Attributes < Sequencer::Unit::Base
  include ::Sequencer::Unit::Import::Common::Model::Mixin::HandleFailure
  prepend ::Sequencer::Unit::Import::Common::Model::Mixin::Skip::Action

  skip_action :skipped, :failed

  uses :mapped, :model_class
  provides :instance

  def process
    return if state.provided?(:instance)
    return if existing_instance.blank?

    state.provide(:instance, existing_instance)
  end

  private

  def attribute
    raise "Missing implementation of '#{__method__}' method for '#{self.class.name}'"
  end

  def attributes
    # alias or alias_method won't work if attribute method
    # is overwritten in inheriting sub-class
    attribute
  end

  def existing_instance
    @existing_instance ||= begin
      Array(attributes).find do |attribute|

        value = mapped[attribute]
        next if value.blank?

        existing_instance = lookup(
          attribute: attribute,
          value:     value
        )

        next if existing_instance.blank?

        # https://stackoverflow.com/a/24901650/7900866
        break existing_instance
      end
    end
  end

  def lookup(attribute:, value:)
    return model_class.identify(value) if model_class.respond_to?(:identify)

    lookup_find_by(attribute, value)
  end

  def lookup_find_by(attribute, value)
    model_class.find_by(attribute => value)
  end
end