class PackageConfig

def guess_default_path
  arch_depended_path = Dir.glob("/usr/lib/*/pkgconfig")
  default_paths = [
    "/usr/local/lib64/pkgconfig",
    "/usr/local/libx32/pkgconfig",
    "/usr/local/lib/pkgconfig",
    "/usr/local/libdata/pkgconfig",
    "/usr/local/share/pkgconfig",
    "/opt/local/lib/pkgconfig",
    *arch_depended_path,
    "/usr/lib64/pkgconfig",
    "/usr/libx32/pkgconfig",
    "/usr/lib/pkgconfig",
    "/usr/libdata/pkgconfig",
    "/usr/X11R6/lib/pkgconfig",
    "/usr/X11R6/share/pkgconfig",
    "/usr/X11/lib/pkgconfig",
    "/opt/X11/lib/pkgconfig",
    "/usr/share/pkgconfig",
  ]
  libdir = ENV["PKG_CONFIG_LIBDIR"]
  default_paths.unshift(libdir) if libdir
  paths = []
  pkg_config_prefix = self.class.native_pkg_config_prefix
  if pkg_config_prefix
    pkg_config_arch_depended_paths =
      Dir.glob((pkg_config_prefix + "lib/*/pkgconfig").to_s)
    paths.concat(pkg_config_arch_depended_paths)
    paths << (pkg_config_prefix + "lib64/pkgconfig").to_s
    paths << (pkg_config_prefix + "libx32/pkgconfig").to_s
    paths << (pkg_config_prefix + "lib/pkgconfig").to_s
    paths << (pkg_config_prefix + "libdata/pkgconfig").to_s
  end
  if /-darwin\d[\d\.]*\z/ =~ RUBY_PLATFORM and
      /\A(\d+\.\d+)/ =~ `sw_vers -productVersion`
    mac_os_version = $1
    homebrew_repository_candidates = []
    if pkg_config_prefix
      brew_path = pkg_config_prefix + "bin" + "brew"
      if brew_path.exist?
        escaped_brew_path = Shellwords.escape(brew_path.to_s)
        homebrew_repository = `#{escaped_brew_path} --repository`.chomp
        homebrew_repository_candidates << Pathname.new(homebrew_repository)
      else
        homebrew_repository_candidates << pkg_config_prefix + "Homebrew"
        homebrew_repository_candidates << pkg_config_prefix
      end
    end
    brew = self.class.__send__(:search_executable_from_path, "brew")
    if brew
      homebrew_repository = `brew --repository`.chomp
      homebrew_repository_candidates << Pathname(homebrew_repository)
    end
    homebrew_repository_candidates.uniq.each do |candidate|
      path = candidate + "Library/Homebrew/os/mac/pkgconfig/#{mac_os_version}"
      paths << path.to_s if path.exist?
    end
  end
  paths.concat(default_paths)
  paths.join(SEPARATOR)
end