yast/yast-yast2

# ***************************************************************************
#
# Copyright (c) 2015 SUSE LLC
# All Rights Reserved.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of version 2 of the GNU General Public License as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.   See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, contact Novell, Inc.
#
# To contact Novell about this file by physical or electronic mail,
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# ***************************************************************************

require "yast"

module Yast2
  # Goal of this module is to provide easy to use api to store id of pre
  # snapshots, so post snapshots can be then easy to make.
  module FsSnapshotStore
    class IOError < StandardError; end

    # Stores pre snapshot with given id and purpose
    # @param[String] purpose of snapshot like "upgrade"
    # @raise[RuntimeError] if writing to file failed
    def self.save(purpose, snapshot_id)
      # Ensure the directory is there (bsc#1159562)
      Yast::SCR.Execute(
        Yast::Path.new(".target.bash"),
        "/bin/mkdir -p #{snapshot_dir_path}"
      )

      result = Yast::SCR.Write(
        Yast::Path.new(".target.string"),
        snapshot_path(purpose),
        snapshot_id.to_s
      )

      raise IOError, "Failed to write Pre Snapshot id for #{purpose} to store. See logs." unless result
    end

    # Loads id of pre snapshot for given purpose
    # @param[String] purpose of snapshot like "upgrade"
    # @raise[RuntimeError] if writing to file failed
    # @return[Fixnum]
    def self.load(purpose)
      content = Yast::SCR.Read(
        Yast::Path.new(".target.string"),
        snapshot_path(purpose)
      )

      raise IOError, "Failed to read Pre Snapshot id for #{purpose} from store. See logs." if !content || content !~ /^\d+$/

      content.to_i
    end

    # Cleans store content of given purpose
    def self.clean(purpose)
      Yast::SCR.Execute(Yast::Path.new(".target.remove"), snapshot_path(purpose))
    end

    # Path where is stored given purpose
    def self.snapshot_path(purpose)
      ::File.join(snapshot_dir_path, "pre_snapshot_#{purpose}.id")
    end
    private_class_method :snapshot_path

    # Path of the directory where the ids of the snapshots are stored
    def self.snapshot_dir_path
      path = "/var/lib/YaST2"

      Yast.import "Stage"
      if Yast::Stage.initial && !Yast::WFM.scr_chrooted?
        Yast.import "Installation"
        path = ::File.join(Yast::Installation.destdir, path)
      end

      path
    end
    private_class_method :snapshot_dir_path
  end
end