# -*- ruby -*-
#--
# Copyright 2006 by Chad Fowler, Rich Kilmer, Jim Weirich and others.
# All rights reserved.
# See LICENSE.txt for permissions.
#++

require 'rbconfig'
require 'thread'

module Gem
  VERSION = '2.4.6'
end

# Must be first since it unloads the prelude from 1.9.2
require 'rubygems/compatibility'

require 'rubygems/defaults'
require 'rubygems/deprecate'
require 'rubygems/errors'

##
# RubyGems is the Ruby standard for publishing and managing third party
# libraries.
#
# For user documentation, see:
#
# * <tt>gem help</tt> and <tt>gem help [command]</tt>
# * {RubyGems User Guide}[http://docs.rubygems.org/read/book/1]
# * {Frequently Asked Questions}[http://docs.rubygems.org/read/book/3]
#
# For gem developer documentation see:
#
# * {Creating Gems}[http://docs.rubygems.org/read/chapter/5]
# * Gem::Specification
# * Gem::Version for version dependency notes
#
# Further RubyGems documentation can be found at:
#
# * {RubyGems Guides}[http://guides.rubygems.org]
# * {RubyGems API}[http://rubygems.rubyforge.org/rdoc] (also available from
#   <tt>gem server</tt>)
#
# == RubyGems Plugins
#
# As of RubyGems 1.3.2, RubyGems will load plugins installed in gems or
# $LOAD_PATH.  Plugins must be named 'rubygems_plugin' (.rb, .so, etc) and
# placed at the root of your gem's #require_path.  Plugins are discovered via
# Gem::find_files then loaded.  Take care when implementing a plugin as your
# plugin file may be loaded multiple times if multiple versions of your gem
# are installed.
#
# For an example plugin, see the graph gem which adds a `gem graph` command.
#
# == RubyGems Defaults, Packaging
#
# RubyGems defaults are stored in rubygems/defaults.rb.  If you're packaging
# RubyGems or implementing Ruby you can change RubyGems' defaults.
#
# For RubyGems packagers, provide lib/rubygems/defaults/operating_system.rb
# and override any defaults from lib/rubygems/defaults.rb.
#
# For Ruby implementers, provide lib/rubygems/defaults/#{RUBY_ENGINE}.rb and
# override any defaults from lib/rubygems/defaults.rb.
#
# If you need RubyGems to perform extra work on install or uninstall, your
# defaults override file can set pre and post install and uninstall hooks.
# See Gem::pre_install, Gem::pre_uninstall, Gem::post_install,
# Gem::post_uninstall.
#
# == Bugs
#
# You can submit bugs to the
# {RubyGems bug tracker}[https://github.com/rubygems/rubygems/issues]
# on GitHub
#
# == Credits
#
# RubyGems is currently maintained by Eric Hodel.
#
# RubyGems was originally developed at RubyConf 2003 by:
#
# * Rich Kilmer  -- rich(at)infoether.com
# * Chad Fowler  -- chad(at)chadfowler.com
# * David Black  -- dblack(at)wobblini.net
# * Paul Brannan -- paul(at)atdesk.com
# * Jim Weirich   -- jim(at)weirichhouse.org
#
# Contributors:
#
# * Gavin Sinclair     -- gsinclair(at)soyabean.com.au
# * George Marrows     -- george.marrows(at)ntlworld.com
# * Dick Davies        -- rasputnik(at)hellooperator.net
# * Mauricio Fernandez -- batsman.geo(at)yahoo.com
# * Simon Strandgaard  -- neoneye(at)adslhome.dk
# * Dave Glasser       -- glasser(at)mit.edu
# * Paul Duncan        -- pabs(at)pablotron.org
# * Ville Aine         -- vaine(at)cs.helsinki.fi
# * Eric Hodel         -- drbrain(at)segment7.net
# * Daniel Berger      -- djberg96(at)gmail.com
# * Phil Hagelberg     -- technomancy(at)gmail.com
# * Ryan Davis         -- ryand-ruby(at)zenspider.com
# * Evan Phoenix       -- evan(at)fallingsnow.net
# * Steve Klabnik      -- steve(at)steveklabnik.com
#
# (If your name is missing, PLEASE let us know!)
#
# See {LICENSE.txt}[rdoc-ref:lib/rubygems/LICENSE.txt] for permissions.
#
# Thanks!
#
# -The RubyGems Team


module Gem
  RUBYGEMS_DIR = File.dirname File.expand_path(__FILE__)

  ##
  # An Array of Regexps that match windows Ruby platforms.

  WIN_PATTERNS = [
    /bccwin/i,
    /cygwin/i,
    /djgpp/i,
    /mingw/i,
    /mswin/i,
    /wince/i,
  ]

  GEM_DEP_FILES = %w[
    gem.deps.rb
    Gemfile
    Isolate
  ]

  ##
  # Subdirectories in a gem repository

  REPOSITORY_SUBDIRECTORIES = %w[
    build_info
    cache
    doc
    extensions
    gems
    specifications
  ]

  ##
  # Subdirectories in a gem repository for default gems

  REPOSITORY_DEFAULT_GEM_SUBDIRECTORIES = %w[
    gems
    specifications/default
  ]

  @@win_platform = nil

  @configuration = nil
  @loaded_specs = {}
  LOADED_SPECS_MUTEX = Mutex.new
  @path_to_default_spec_map = {}
  @platforms = []
  @ruby = nil
  @ruby_api_version = nil
  @sources = nil

  @post_build_hooks     ||= []
  @post_install_hooks   ||= []
  @post_uninstall_hooks ||= []
  @pre_uninstall_hooks  ||= []
  @pre_install_hooks    ||= []
  @pre_reset_hooks      ||= []
  @post_reset_hooks     ||= []

  ##
  # Try to activate a gem containing +path+. Returns true if
  # activation succeeded or wasn't needed because it was already
  # activated. Returns false if it can't find the path in a gem.

  def self.try_activate path
    # finds the _latest_ version... regardless of loaded specs and their deps
    # if another gem had a requirement that would mean we shouldn't
    # activate the latest version, then either it would already be activated
    # or if it was ambiguous (and thus unresolved) the code in our custom
    # require will try to activate the more specific version.

    spec = Gem::Specification.find_inactive_by_path path

    unless spec
      spec = Gem::Specification.find_by_path path
      return true if spec && spec.activated?
      return false
    end

    begin
      spec.activate
    rescue Gem::LoadError # this could fail due to gem dep collisions, go lax
      Gem::Specification.find_by_name(spec.name).activate
    end

    return true
  end

  def self.needs
    rs = Gem::RequestSet.new

    yield rs

    finish_resolve rs
  end

  def self.finish_resolve(request_set=Gem::RequestSet.new)
    request_set.import Gem::Specification.unresolved_deps.values

    request_set.resolve_current.each do |s|
      s.full_spec.activate
    end
  end

  ##
  # Find the full path to the executable for gem +name+.  If the +exec_name+
  # is not given, the gem's default_executable is chosen, otherwise the
  # specified executable's path is returned.  +requirements+ allows
  # you to specify specific gem versions.

  def self.bin_path(name, exec_name = nil, *requirements)
    # TODO: fails test_self_bin_path_bin_file_gone_in_latest
    # Gem::Specification.find_by_name(name, *requirements).bin_file exec_name

    raise ArgumentError, "you must supply exec_name" unless exec_name

    requirements = Gem::Requirement.default if
      requirements.empty?

    dep = Gem::Dependency.new name, requirements

    loaded = Gem.loaded_specs[name]

    return loaded.bin_file exec_name if loaded && dep.matches_spec?(loaded)

    specs = dep.matching_specs(true)

    raise Gem::GemNotFoundException,
          "can't find gem #{name} (#{requirements})" if specs.empty?

    specs = specs.find_all { |spec|
      spec.executables.include? exec_name
    } if exec_name

    unless spec = specs.last
      msg = "can't find gem #{name} (#{requirements}) with executable #{exec_name}"
      raise Gem::GemNotFoundException, msg
    end

    spec.bin_file exec_name
  end

  ##
  # The mode needed to read a file as straight binary.

  def self.binary_mode
    'rb'
  end

  ##
  # The path where gem executables are to be installed.

  def self.bindir(install_dir=Gem.dir)
    return File.join install_dir, 'bin' unless
      install_dir.to_s == Gem.default_dir.to_s
    Gem.default_bindir
  end

  ##
  # Reset the +dir+ and +path+ values.  The next time +dir+ or +path+
  # is requested, the values will be calculated from scratch.  This is
  # mainly used by the unit tests to provide test isolation.

  def self.clear_paths
    @paths         = nil
    @user_home     = nil
    Gem::Specification.reset
    Gem::Security.reset if defined?(Gem::Security)
  end

  ##
  # The path to standard location of the user's .gemrc file.

  def self.config_file
    @config_file ||= File.join Gem.user_home, '.gemrc'
  end

  ##
  # The standard configuration object for gems.

  def self.configuration
    @configuration ||= Gem::ConfigFile.new []
  end

  ##
  # Use the given configuration object (which implements the ConfigFile
  # protocol) as the standard configuration object.

  def self.configuration=(config)
    @configuration = config
  end

  ##
  # The path to the data directory specified by the gem name.  If the
  # package is not available as a gem, return nil.

  def self.datadir(gem_name)
# TODO: deprecate and move to Gem::Specification
#       and drop the extra ", gem_name" which is uselessly redundant
    spec = @loaded_specs[gem_name]
    return nil if spec.nil?
    File.join spec.full_gem_path, "data", gem_name
  end

  ##
  # A Zlib::Deflate.deflate wrapper

  def self.deflate(data)
    require 'zlib'
    Zlib::Deflate.deflate data
  end

  # Retrieve the PathSupport object that RubyGems uses to
  # lookup files.

  def self.paths
    @paths ||= Gem::PathSupport.new
  end

  # Initialize the filesystem paths to use from +env+.
  # +env+ is a hash-like object (typically ENV) that
  # is queried for 'GEM_HOME', 'GEM_PATH', and 'GEM_SPEC_CACHE'

  def self.paths=(env)
    clear_paths
    @paths = Gem::PathSupport.new env
    Gem::Specification.dirs = @paths.path
  end

  ##
  # The path where gems are to be installed.
  #--
  # FIXME deprecate these once everything else has been done -ebh

  def self.dir
    paths.home
  end

  def self.path
    paths.path
  end

  def self.spec_cache_dir
    paths.spec_cache_dir
  end

  ##
  # Quietly ensure the Gem directory +dir+ contains all the proper
  # subdirectories.  If we can't create a directory due to a permission
  # problem, then we will silently continue.
  #
  # If +mode+ is given, missing directories are created with this mode.
  #
  # World-writable directories will never be created.

  def self.ensure_gem_subdirectories dir = Gem.dir, mode = nil
    ensure_subdirectories(dir, mode, REPOSITORY_SUBDIRECTORIES)
  end

  ##
  # Quietly ensure the Gem directory +dir+ contains all the proper
  # subdirectories for handling default gems.  If we can't create a
  # directory due to a permission problem, then we will silently continue.
  #
  # If +mode+ is given, missing directories are created with this mode.
  #
  # World-writable directories will never be created.

  def self.ensure_default_gem_subdirectories dir = Gem.dir, mode = nil
    ensure_subdirectories(dir, mode, REPOSITORY_DEFAULT_GEM_SUBDIRECTORIES)
  end

  def self.ensure_subdirectories dir, mode, subdirs # :nodoc:
    old_umask = File.umask
    File.umask old_umask | 002

    require 'fileutils'

    options = {}

    options[:mode] = mode if mode

    subdirs.each do |name|
      subdir = File.join dir, name
      next if File.exist? subdir
      FileUtils.mkdir_p subdir, options rescue nil
    end
  ensure
    File.umask old_umask
  end

  ##
  # The extension API version of ruby.  This includes the static vs non-static
  # distinction as extensions cannot be shared between the two.

  def self.extension_api_version # :nodoc:
    if 'no' == RbConfig::CONFIG['ENABLE_SHARED'] then
      "#{ruby_api_version}-static"
    else
      ruby_api_version
    end
  end

  ##
  # Returns a list of paths matching +glob+ that can be used by a gem to pick
  # up features from other gems.  For example:
  #
  #   Gem.find_files('rdoc/discover').each do |path| load path end
  #
  # if +check_load_path+ is true (the default), then find_files also searches
  # $LOAD_PATH for files as well as gems.
  #
  # Note that find_files will return all files even if they are from different
  # versions of the same gem.  See also find_latest_files

  def self.find_files(glob, check_load_path=true)
    files = []

    files = find_files_from_load_path glob if check_load_path

    files.concat Gem::Specification.map { |spec|
      spec.matches_for_glob("#{glob}#{Gem.suffix_pattern}")
    }.flatten

    # $LOAD_PATH might contain duplicate entries or reference
    # the spec dirs directly, so we prune.
    files.uniq! if check_load_path

    return files
  end

  def self.find_files_from_load_path glob # :nodoc:
    $LOAD_PATH.map { |load_path|
      Dir["#{File.expand_path glob, load_path}#{Gem.suffix_pattern}"]
    }.flatten.select { |file| File.file? file.untaint }
  end

  ##
  # Returns a list of paths matching +glob+ from the latest gems that can be
  # used by a gem to pick up features from other gems.  For example:
  #
  #   Gem.find_latest_files('rdoc/discover').each do |path| load path end
  #
  # if +check_load_path+ is true (the default), then find_latest_files also
  # searches $LOAD_PATH for files as well as gems.
  #
  # Unlike find_files, find_latest_files will return only files from the
  # latest version of a gem.

  def self.find_latest_files(glob, check_load_path=true)
    files = []

    files = find_files_from_load_path glob if check_load_path

    files.concat Gem::Specification.latest_specs(true).map { |spec|
      spec.matches_for_glob("#{glob}#{Gem.suffix_pattern}")
    }.flatten

    # $LOAD_PATH might contain duplicate entries or reference
    # the spec dirs directly, so we prune.
    files.uniq! if check_load_path

    return files
  end

  ##
  # Finds the user's home directory.
  #--
  # Some comments from the ruby-talk list regarding finding the home
  # directory:
  #
  #   I have HOME, USERPROFILE and HOMEDRIVE + HOMEPATH. Ruby seems
  #   to be depending on HOME in those code samples. I propose that
  #   it should fallback to USERPROFILE and HOMEDRIVE + HOMEPATH (at
  #   least on Win32).
  #++
  #--
  #
  # FIXME move to pathsupport
  #
  #++

  def self.find_home
    windows = File::ALT_SEPARATOR
    if not windows or RUBY_VERSION >= '1.9' then
      File.expand_path "~"
    else
      ['HOME', 'USERPROFILE'].each do |key|
        return File.expand_path ENV[key] if ENV[key]
      end

      if ENV['HOMEDRIVE'] && ENV['HOMEPATH'] then
        File.expand_path "#{ENV['HOMEDRIVE']}#{ENV['HOMEPATH']}"
      end
    end
  rescue
    if windows then
      File.expand_path File.join(ENV['HOMEDRIVE'] || ENV['SystemDrive'], '/')
    else
      File.expand_path "/"
    end
  end

  private_class_method :find_home

  # FIXME deprecate these in 3.0

  ##
  # Zlib::GzipReader wrapper that unzips +data+.

  def self.gunzip(data)
    require 'rubygems/util'
    Gem::Util.gunzip data
  end

  ##
  # Zlib::GzipWriter wrapper that zips +data+.

  def self.gzip(data)
    require 'rubygems/util'
    Gem::Util.gzip data
  end

  ##
  # A Zlib::Inflate#inflate wrapper

  def self.inflate(data)
    require 'rubygems/util'
    Gem::Util.inflate data
  end

  ##
  # Top level install helper method. Allows you to install gems interactively:
  #
  #   % irb
  #   >> Gem.install "minitest"
  #   Fetching: minitest-3.0.1.gem (100%)
  #   => [#<Gem::Specification:0x1013b4528 @name="minitest", ...>]

  def self.install name, version = Gem::Requirement.default, *options
    require "rubygems/dependency_installer"
    inst = Gem::DependencyInstaller.new(*options)
    inst.install name, version
    inst.installed_gems
  end

  ##
  # Get the default RubyGems API host. This is normally
  # <tt>https://rubygems.org</tt>.

  def self.host
    # TODO: move to utils
    @host ||= Gem::DEFAULT_HOST
  end

  ## Set the default RubyGems API host.

  def self.host= host
    # TODO: move to utils
    @host = host
  end

  ##
  # The index to insert activated gem paths into the $LOAD_PATH. The activated
  # gem's paths are inserted before site lib directory by default.

  def self.load_path_insert_index
    index = $LOAD_PATH.index RbConfig::CONFIG['sitelibdir']

    index
  end

  @yaml_loaded = false

  ##
  # Loads YAML, preferring Psych

  def self.load_yaml
    return if @yaml_loaded
    return unless defined?(gem)

    test_syck = ENV['TEST_SYCK']

    unless test_syck
      begin
        gem 'psych', '>= 1.2.1'
      rescue Gem::LoadError
        # It's OK if the user does not have the psych gem installed.  We will
        # attempt to require the stdlib version
      end

      begin
        # Try requiring the gem version *or* stdlib version of psych.
        require 'psych'
      rescue ::LoadError
        # If we can't load psych, thats fine, go on.
      else
        # If 'yaml' has already been required, then we have to
        # be sure to switch it over to the newly loaded psych.
        if defined?(YAML::ENGINE) && YAML::ENGINE.yamler != "psych"
          YAML::ENGINE.yamler = "psych"
        end

        require 'rubygems/psych_additions'
        require 'rubygems/psych_tree'
      end
    end

    require 'yaml'

    # If we're supposed to be using syck, then we may have to force
    # activate it via the YAML::ENGINE API.
    if test_syck and defined?(YAML::ENGINE)
      YAML::ENGINE.yamler = "syck" unless YAML::ENGINE.syck?
    end

    # Now that we're sure some kind of yaml library is loaded, pull
    # in our hack to deal with Syck's DefaultKey ugliness.
    require 'rubygems/syck_hack'

    @yaml_loaded = true
  end

  ##
  # The file name and line number of the caller of the caller of this method.

  def self.location_of_caller
    caller[1] =~ /(.*?):(\d+).*?$/i
    file = $1
    lineno = $2.to_i

    [file, lineno]
  end

  ##
  # The version of the Marshal format for your Ruby.

  def self.marshal_version
    "#{Marshal::MAJOR_VERSION}.#{Marshal::MINOR_VERSION}"
  end

  ##
  # Set array of platforms this RubyGems supports (primarily for testing).

  def self.platforms=(platforms)
    @platforms = platforms
  end

  ##
  # Array of platforms this RubyGems supports.

  def self.platforms
    @platforms ||= []
    if @platforms.empty?
      @platforms = [Gem::Platform::RUBY, Gem::Platform.local]
    end
    @platforms
  end

  ##
  # Adds a post-build hook that will be passed an Gem::Installer instance
  # when Gem::Installer#install is called.  The hook is called after the gem
  # has been extracted and extensions have been built but before the
  # executables or gemspec has been written.  If the hook returns +false+ then
  # the gem's files will be removed and the install will be aborted.

  def self.post_build(&hook)
    @post_build_hooks << hook
  end

  ##
  # Adds a post-install hook that will be passed an Gem::Installer instance
  # when Gem::Installer#install is called

  def self.post_install(&hook)
    @post_install_hooks << hook
  end

  ##
  # Adds a post-installs hook that will be passed a Gem::DependencyInstaller
  # and a list of installed specifications when
  # Gem::DependencyInstaller#install is complete

  def self.done_installing(&hook)
    @done_installing_hooks << hook
  end

  ##
  # Adds a hook that will get run after Gem::Specification.reset is
  # run.

  def self.post_reset(&hook)
    @post_reset_hooks << hook
  end

  ##
  # Adds a post-uninstall hook that will be passed a Gem::Uninstaller instance
  # and the spec that was uninstalled when Gem::Uninstaller#uninstall is
  # called

  def self.post_uninstall(&hook)
    @post_uninstall_hooks << hook
  end

  ##
  # Adds a pre-install hook that will be passed an Gem::Installer instance
  # when Gem::Installer#install is called.  If the hook returns +false+ then
  # the install will be aborted.

  def self.pre_install(&hook)
    @pre_install_hooks << hook
  end

  ##
  # Adds a hook that will get run before Gem::Specification.reset is
  # run.

  def self.pre_reset(&hook)
    @pre_reset_hooks << hook
  end

  ##
  # Adds a pre-uninstall hook that will be passed an Gem::Uninstaller instance
  # and the spec that will be uninstalled when Gem::Uninstaller#uninstall is
  # called

  def self.pre_uninstall(&hook)
    @pre_uninstall_hooks << hook
  end

  ##
  # The directory prefix this RubyGems was installed at. If your
  # prefix is in a standard location (ie, rubygems is installed where
  # you'd expect it to be), then prefix returns nil.

  def self.prefix
    prefix = File.dirname RUBYGEMS_DIR

    if prefix != File.expand_path(RbConfig::CONFIG['sitelibdir']) and
       prefix != File.expand_path(RbConfig::CONFIG['libdir']) and
       'lib' == File.basename(RUBYGEMS_DIR) then
      prefix
    end
  end

  ##
  # Refresh available gems from disk.

  def self.refresh
    Gem::Specification.reset
  end

  ##
  # Safely read a file in binary mode on all platforms.

  def self.read_binary(path)
    open path, 'rb+' do |f|
      f.flock(File::LOCK_EX)
      f.read
    end
  rescue Errno::EACCES
    open path, 'rb' do |f|
      f.read
    end
  end

  ##
  # The path to the running Ruby interpreter.

  def self.ruby
    if @ruby.nil? then
      @ruby = File.join(RbConfig::CONFIG['bindir'],
                        "#{RbConfig::CONFIG['ruby_install_name']}#{RbConfig::CONFIG['EXEEXT']}")

      @ruby = "\"#{@ruby}\"" if @ruby =~ /\s/
    end

    @ruby
  end

  ##
  # Returns a String containing the API compatibility version of Ruby

  def self.ruby_api_version
    @ruby_api_version ||= RbConfig::CONFIG['ruby_version'].dup
  end

  ##
  # Returns the latest release-version specification for the gem +name+.

  def self.latest_spec_for name
    dependency   = Gem::Dependency.new name
    fetcher      = Gem::SpecFetcher.fetcher
    spec_tuples, = fetcher.spec_for_dependency dependency

    spec, = spec_tuples.first

    spec
  end

  ##
  # Returns the latest release version of RubyGems.

  def self.latest_rubygems_version
    latest_version_for('rubygems-update') or
      raise "Can't find 'rubygems-update' in any repo. Check `gem source list`."
  end

  ##
  # Returns the version of the latest release-version of gem +name+

  def self.latest_version_for name
    spec = latest_spec_for name
    spec and spec.version
  end

  ##
  # A Gem::Version for the currently running Ruby.

  def self.ruby_version
    return @ruby_version if defined? @ruby_version
    version = RUBY_VERSION.dup

    if defined?(RUBY_PATCHLEVEL) && RUBY_PATCHLEVEL != -1 then
      version << ".#{RUBY_PATCHLEVEL}"
    elsif defined?(RUBY_REVISION) then
      version << ".dev.#{RUBY_REVISION}"
    end

    @ruby_version = Gem::Version.new version
  end

  ##
  # A Gem::Version for the currently running RubyGems

  def self.rubygems_version
    return @rubygems_version if defined? @rubygems_version
    @rubygems_version = Gem::Version.new Gem::VERSION
  end

  ##
  # Returns an Array of sources to fetch remote gems from. Uses
  # default_sources if the sources list is empty.

  def self.sources
    @sources ||= Gem::SourceList.from(default_sources)
  end

  ##
  # Need to be able to set the sources without calling
  # Gem.sources.replace since that would cause an infinite loop.
  #
  # DOC: This comment is not documentation about the method itself, it's
  # more of a code comment about the implementation.

  def self.sources= new_sources
    if !new_sources
      @sources = nil
    else
      @sources = Gem::SourceList.from(new_sources)
    end
  end

  ##
  # Glob pattern for require-able path suffixes.

  def self.suffix_pattern
    @suffix_pattern ||= "{#{suffixes.join(',')}}"
  end

  ##
  # Suffixes for require-able paths.

  def self.suffixes
    @suffixes ||= ['',
                   '.rb',
                   *%w(DLEXT DLEXT2).map { |key|
                     val = RbConfig::CONFIG[key]
                     next unless val and not val.empty?
                     ".#{val}"
                   }
                  ].compact.uniq
  end

  ##
  # Prints the amount of time the supplied block takes to run using the debug
  # UI output.

  def self.time(msg, width = 0, display = Gem.configuration.verbose)
    now = Time.now

    value = yield

    elapsed = Time.now - now

    ui.say "%2$*1$s: %3$3.3fs" % [-width, msg, elapsed] if display

    value
  end

  ##
  # Lazily loads DefaultUserInteraction and returns the default UI.

  def self.ui
    require 'rubygems/user_interaction'

    Gem::DefaultUserInteraction.ui
  end

  ##
  # Use the +home+ and +paths+ values for Gem.dir and Gem.path.  Used mainly
  # by the unit tests to provide environment isolation.

  def self.use_paths(home, *paths)
    paths = nil if paths == [nil]
    paths = paths.first if Array === Array(paths).first
    self.paths = { "GEM_HOME" => home, "GEM_PATH" => paths }
  end

  ##
  # The home directory for the user.

  def self.user_home
    @user_home ||= find_home.untaint
  end

  ##
  # Is this a windows platform?

  def self.win_platform?
    if @@win_platform.nil? then
      ruby_platform = RbConfig::CONFIG['host_os']
      @@win_platform = !!WIN_PATTERNS.find { |r| ruby_platform =~ r }
    end

    @@win_platform
  end

  ##
  # Load +plugins+ as Ruby files

  def self.load_plugin_files plugins # :nodoc:
    plugins.each do |plugin|

      # Skip older versions of the GemCutter plugin: Its commands are in
      # RubyGems proper now.

      next if plugin =~ /gemcutter-0\.[0-3]/

      begin
        load plugin
      rescue ::Exception => e
        details = "#{plugin.inspect}: #{e.message} (#{e.class})"
        warn "Error loading RubyGems plugin #{details}"
      end
    end
  end

  ##
  # Find the 'rubygems_plugin' files in the latest installed gems and load
  # them

  def self.load_plugins
    # Remove this env var by at least 3.0
    if ENV['RUBYGEMS_LOAD_ALL_PLUGINS']
      load_plugin_files find_files('rubygems_plugin', false)
    else
      load_plugin_files find_latest_files('rubygems_plugin', false)
    end
  end

  ##
  # Find all 'rubygems_plugin' files in $LOAD_PATH and load them

  def self.load_env_plugins
    path = "rubygems_plugin"

    files = []
    $LOAD_PATH.each do |load_path|
      globbed = Dir["#{File.expand_path path, load_path}#{Gem.suffix_pattern}"]

      globbed.each do |load_path_file|
        files << load_path_file if File.file?(load_path_file.untaint)
      end
    end

    load_plugin_files files
  end

  ##
  # Looks for a gem dependency file at +path+ and activates the gems in the
  # file if found.  If the file is not found an ArgumentError is raised.
  #
  # If +path+ is not given the RUBYGEMS_GEMDEPS environment variable is used,
  # but if no file is found no exception is raised.
  #
  # If '-' is given for +path+ RubyGems searches up from the current working
  # directory for gem dependency files (gem.deps.rb, Gemfile, Isolate) and
  # activates the gems in the first one found.
  #
  # You can run this automatically when rubygems starts.  To enable, set
  # the <code>RUBYGEMS_GEMDEPS</code> environment variable to either the path
  # of your gem dependencies file or "-" to auto-discover in parent
  # directories.
  #
  # NOTE: Enabling automatic discovery on multiuser systems can lead to
  # execution of arbitrary code when used from directories outside your
  # control.

  def self.use_gemdeps path = nil
    raise_exception = path

    path ||= ENV['RUBYGEMS_GEMDEPS']
    return unless path

    path = path.dup

    if path == "-" then
      require 'rubygems/util'

      Gem::Util.traverse_parents Dir.pwd do |directory|
        dep_file = GEM_DEP_FILES.find { |f| File.file?(f) }

        next unless dep_file

        path = File.join directory, dep_file
        break
      end
    end

    path.untaint

    unless File.file? path then
      return unless raise_exception

      raise ArgumentError, "Unable to find gem dependencies file at #{path}"
    end

    rs = Gem::RequestSet.new
    rs.load_gemdeps path

    rs.resolve_current.map do |s|
      sp = s.full_spec
      sp.activate
      sp
    end
  rescue Gem::LoadError, Gem::UnsatisfiableDependencyError => e
    warn e.message
    warn "You may need to `gem install -g` to install missing gems"
    warn ""
  end

  class << self
    ##
    # TODO remove with RubyGems 3.0

    alias detect_gemdeps use_gemdeps # :nodoc:
  end

  # FIX: Almost everywhere else we use the `def self.` way of defining class
  # methods, and then we switch over to `class << self` here. Pick one or the
  # other.
  class << self

    ##
    # Hash of loaded Gem::Specification keyed by name

    attr_reader :loaded_specs

    ##
    # Register a Gem::Specification for default gem.
    #
    # Two formats for the specification are supported:
    #
    # * MRI 2.0 style, where spec.files contains unprefixed require names.
    #   The spec's filenames will be registered as-is.
    # * New style, where spec.files contains files prefixed with paths
    #   from spec.require_paths. The prefixes are stripped before
    #   registering the spec's filenames. Unprefixed files are omitted.
    #

    def register_default_spec(spec)
      new_format = Gem.default_gems_use_full_paths? || spec.require_paths.any? {|path| spec.files.any? {|f| f.start_with? path } }

      if new_format
        prefix_group = spec.require_paths.map {|f| f + "/"}.join("|")
        prefix_pattern = /^(#{prefix_group})/
      end

      spec.files.each do |file|
        if new_format
          file = file.sub(prefix_pattern, "")
          next unless $~
        end

        @path_to_default_spec_map[file] = spec
      end
    end

    ##
    # Find a Gem::Specification of default gem from +path+

    def find_unresolved_default_spec(path)
      Gem.suffixes.each do |suffix|
        spec = @path_to_default_spec_map["#{path}#{suffix}"]
        return spec if spec
      end
      nil
    end

    ##
    # Remove needless Gem::Specification of default gem from
    # unresolved default gem list

    def remove_unresolved_default_spec(spec)
      spec.files.each do |file|
        @path_to_default_spec_map.delete(file)
      end
    end

    ##
    # Clear default gem related variables. It is for test

    def clear_default_specs
      @path_to_default_spec_map.clear
    end

    ##
    # The list of hooks to be run after Gem::Installer#install extracts files
    # and builds extensions

    attr_reader :post_build_hooks

    ##
    # The list of hooks to be run after Gem::Installer#install completes
    # installation

    attr_reader :post_install_hooks

    ##
    # The list of hooks to be run after Gem::DependencyInstaller installs a
    # set of gems

    attr_reader :done_installing_hooks

    ##
    # The list of hooks to be run after Gem::Specification.reset is run.

    attr_reader :post_reset_hooks

    ##
    # The list of hooks to be run after Gem::Uninstaller#uninstall completes
    # installation

    attr_reader :post_uninstall_hooks

    ##
    # The list of hooks to be run before Gem::Installer#install does any work

    attr_reader :pre_install_hooks

    ##
    # The list of hooks to be run before Gem::Specification.reset is run.

    attr_reader :pre_reset_hooks

    ##
    # The list of hooks to be run before Gem::Uninstaller#uninstall does any
    # work

    attr_reader :pre_uninstall_hooks
  end

  ##
  # Location of Marshal quick gemspecs on remote repositories

  MARSHAL_SPEC_DIR = "quick/Marshal.#{Gem.marshal_version}/"

  autoload :ConfigFile,         'rubygems/config_file'
  autoload :Dependency,         'rubygems/dependency'
  autoload :DependencyList,     'rubygems/dependency_list'
  autoload :DependencyResolver, 'rubygems/resolver'
  autoload :Installer,          'rubygems/installer'
  autoload :PathSupport,        'rubygems/path_support'
  autoload :Platform,           'rubygems/platform'
  autoload :RequestSet,         'rubygems/request_set'
  autoload :Requirement,        'rubygems/requirement'
  autoload :Resolver,           'rubygems/resolver'
  autoload :Source,             'rubygems/source'
  autoload :SourceList,         'rubygems/source_list'
  autoload :SpecFetcher,        'rubygems/spec_fetcher'
  autoload :Specification,      'rubygems/specification'
  autoload :Version,            'rubygems/version'

  require "rubygems/specification"
end

require 'rubygems/exceptions'

# REFACTOR: This should be pulled out into some kind of hacks file.
gem_preluded = Gem::GEM_PRELUDE_SUCKAGE and defined? Gem
unless gem_preluded then # TODO: remove guard after 1.9.2 dropped
  begin
    ##
    # Defaults the operating system (or packager) wants to provide for RubyGems.

    require 'rubygems/defaults/operating_system'
  rescue LoadError
  end

  if defined?(RUBY_ENGINE) then
    begin
      ##
      # Defaults the Ruby implementation wants to provide for RubyGems

      require "rubygems/defaults/#{RUBY_ENGINE}"
    rescue LoadError
    end
  end
end

##
# Loads the default specs.
Gem::Specification.load_defaults

require 'rubygems/core_ext/kernel_gem'
require 'rubygems/core_ext/kernel_require'

Gem.use_gemdeps

