class Gem::Commands::UpdateCommand

def arguments # :nodoc:
  "GEMNAME       name of gem to update"
end

def defaults_str # :nodoc:
  "--document --no-force --install-dir #{Gem.dir}"
end

def execute
  hig = {}
  if options[:system] then
    update_rubygems
    return
  else
    say "Updating installed gems"
    hig = {} # highest installed gems
    Gem::Specification.each do |spec|
      if hig[spec.name].nil? or hig[spec.name].version < spec.version then
        hig[spec.name] = spec
      end
    end
  end
  gems_to_update = which_to_update hig, options[:args].uniq
  updated = update_gems gems_to_update
  if updated.empty? then
    say "Nothing to update"
  else
    say "Gems updated: #{updated.map { |spec| spec.name }.join ' '}"
  end
end

def initialize
  super 'update', 'Update installed gems to the latest version',
    :document => %w[rdoc ri],
    :force    => false
  add_install_update_options
  OptionParser.accept Gem::Version do |value|
    Gem::Version.new value
    value
  end
  add_option('--system [VERSION]', Gem::Version,
             'Update the RubyGems system software') do |value, options|
    value = true unless value
    options[:system] = value
  end
  add_local_remote_options
  add_platform_option
  add_prerelease_option "as update targets"
  @updated   = []
  @installer = Gem::DependencyInstaller.new options
end

def update_gem name, version = Gem::Requirement.default
  return if @updated.any? { |spec| spec.name == name }
  success = false
  say "Updating #{name}"
  begin
    @installer.install name, version
    success = true
  rescue Gem::InstallError => e
    alert_error "Error installing #{name}:\n\t#{e.message}"
    success = false
  end
  @installer.installed_gems.each do |spec|
    @updated << spec
  end
end

def update_gems gems_to_update
  gems_to_update.uniq.sort.each do |(name, version)|
    update_gem name, version
  end
  @updated
end

def update_rubygems
  unless options[:args].empty? then
    alert_error "Gem names are not allowed with the --system option"
    terminate_interaction 1
  end
  options[:user_install] = false
  # TODO: rename version and other variable name conflicts
  # TODO: get rid of all this indirection on name and other BS
  version = options[:system]
  if version == true then
    version     = Gem::Version.new     Gem::VERSION
    requirement = Gem::Requirement.new ">= #{Gem::VERSION}"
  else
    version     = Gem::Version.new     version
    requirement = Gem::Requirement.new version
  end
  rubygems_update         = Gem::Specification.new
  rubygems_update.name    = 'rubygems-update'
  rubygems_update.version = version
  hig = {
    'rubygems-update' => rubygems_update
  }
  gems_to_update = which_to_update hig, options[:args], :system
  name, up_ver   = gems_to_update.first
  current_ver    = Gem::Version.new Gem::VERSION
  target = if options[:system] == true then
             up_ver
           else
             version
           end
  if current_ver == target then
    # if options[:system] != true and version == current_ver then
    say "Latest version currently installed. Aborting."
    terminate_interaction
  end
  update_gem name, target
  installed_gems = Gem::Specification.find_all_by_name 'rubygems-update', requirement
  version        = installed_gems.last.version
  args = []
  args << '--prefix' << Gem.prefix if Gem.prefix
  # TODO use --document for >= 1.9 , --no-rdoc --no-ri < 1.9
  args << '--no-rdoc' unless options[:document].include? 'rdoc'
  args << '--no-ri'   unless options[:document].include? 'ri'
  args << '--no-format-executable' if options[:no_format_executable]
  update_dir = File.join Gem.dir, 'gems', "rubygems-update-#{version}"
  Dir.chdir update_dir do
    say "Installing RubyGems #{version}"
    setup_cmd = "#{Gem.ruby} setup.rb #{args.join ' '}"
    # Make sure old rubygems isn't loaded
    old = ENV["RUBYOPT"]
    ENV.delete("RUBYOPT") if old
    installed = system setup_cmd
    say "RubyGems system software updated" if installed
    ENV["RUBYOPT"] = old if old
  end
end

def usage # :nodoc:
  "#{program_name} GEMNAME [GEMNAME ...]"
end

def which_to_update highest_installed_gems, gem_names, system = false
  result = []
  highest_installed_gems.each do |l_name, l_spec|
    next if not gem_names.empty? and
            gem_names.all? { |name| /#{name}/ !~ l_spec.name }
    dependency = Gem::Dependency.new l_spec.name, "> #{l_spec.version}"
    dependency.prerelease = options[:prerelease]
    fetcher = Gem::SpecFetcher.fetcher
    spec_tuples, _ = fetcher.search_for_dependency dependency
    matching_gems = spec_tuples.select do |g,_|
      g.name == l_name and g.match_platform?
    end
    highest_remote_gem = matching_gems.sort_by { |g,_| g.version }.last
    highest_remote_gem ||= [Gem::NameTuple.null]
    highest_remote_ver = highest_remote_gem.first.version
    if system or (l_spec.version < highest_remote_ver) then
      result << [l_spec.name, [l_spec.version, highest_remote_ver].max]
    end
  end
  result
end