# frozen_string_literal: true

# The global history of record versions implemented through undo logs.
module Innodb
  class History
    def initialize(innodb_system)
      @innodb_system = innodb_system
    end

    # A helper to get to the trx_sys page in the Innodb::System.
    def trx_sys
      @innodb_system.system_space.trx_sys
    end

    # A helper to get to the history_list of a given space_id and page number.
    def history_list(space_id, page_number)
      @innodb_system.space(space_id).page(page_number).history_list
    end

    # Iterate through all history lists (one per rollback segment, nominally
    # there are 128 rollback segments).
    def each_history_list
      return enum_for(:each_history_list) unless block_given?

      trx_sys.rsegs.each do |slot|
        yield history_list(slot[:space_id], slot[:page_number])
      end
    end
  end
end