module Facter
  if not defined? FACTERVERSION then
    FACTERVERSION = '1.7.3'
  end

  ##
  # version is a public API method intended to always provide a fast and
  # lightweight way to determine the version of Facter.
  #
  # The intent is that software external to Facter be able to determine the
  # Facter version with no side-effects.  The expected use is:
  #
  #     require 'facter/version'
  #     version = Facter.version
  #
  # This function has the following ordering precedence.  This precedence list
  # is designed to facilitate automated packaging tasks by simply writing to
  # the VERSION file in the same directory as this source file.
  #
  #  1. If a version has been explicitly assigned using the Facter.version=
  #     method, return that version.
  #  2. If there is a VERSION file, read the contents, trim any
  #     trailing whitespace, and return that version string.
  #  3. Return the value of the Facter::FACTERVERSION constant hard-coded into
  #     the source code.
  #
  # If there is no VERSION file, the method must return the version string of
  # the nearest parent version that is an officially released version.  That is
  # to say, if a branch named 3.1.x contains 25 patches on top of the most
  # recent official release of 3.1.1, then the version method must return the
  # string "3.1.1" if no "VERSION" file is present.
  #
  # By design the version identifier is _not_ intended to vary during the life
  # a process.  There is no guarantee provided that writing to the VERSION file
  # while a Puppet process is running will cause the version string to be
  # updated.  On the contrary, the contents of the VERSION are cached to reduce
  # filesystem accesses.
  #
  # The VERSION file is intended to be used by package maintainers who may be
  # applying patches or otherwise changing the software version in a manner
  # that warrants a different software version identifier.  The VERSION file is
  # intended to be managed and owned by the release process and packaging
  # related tasks, and as such should not reside in version control.  The
  # FACTERVERSION constant is intended to be version controlled in history.
  #
  # Ideally, this behavior will allow package maintainers to precisely specify
  # the version of the software they're packaging as in the following example:
  #
  #     $ git describe > lib/facter/VERSION
  #     $ ruby -r facter -e 'puts Facter.version'
  #     1.6.14-6-g66f2c99
  #
  # @api public
  #
  # @return [String] containing the facter version, e.g. "1.6.14"
  def self.version
    version_file = File.join(File.dirname(__FILE__), 'VERSION')
    return @facter_version if @facter_version
    if version = read_version_file(version_file)
      @facter_version = version
    end
    @facter_version ||= FACTERVERSION
  end

  def self.version=(version)
    @facter_version = version
  end

  ##
  # read_version_file reads the content of the "VERSION" file that lives in the
  # same directory as this source code file.
  #
  # @api private
  #
  # @return [String] for example: "1.6.14-6-gea42046" or nil if the VERSION
  #   file does not exist.
  def self.read_version_file(path)
    if File.exists?(path)
      File.read(path).chomp
    end
  end
  private_class_method :read_version_file
end
