#!/usr/bin/env ruby
# virtualrb - Virtualize Ruby installations
#
# Copyright (C) 2008  Christian Neukirchen <chneukirchen@gmail.com>
# Licensed under the same terms as Ruby itself.
#
# Idea inspired by Python's virtualenv: http://pypi.python.org/pypi/virtualenv
 
VIRTUALRB_VERSION = "0.1"
 
require 'rbconfig'
if defined? RUBY_VIRTUALRB
  abort "* Don't run virtual.rb from a virtualized ruby, or hell will break lose."
end
 
require 'optparse'
require 'fileutils'
 
def find_ruby
  File.join(Config::CONFIG['bindir'], Config::CONFIG['ruby_install_name'])
end
 
def find_rbconfig(ruby=find_ruby)
  eval(`#{ruby} -e 'p $:'`).
    map { |dir| dir + "/rbconfig.rb" }.
    find { |file| File.exist?(file) }
end
 
gems = false
gemversion = ">=0"
ruby = find_ruby
inherit = true
 
opts = OptionParser.new("", 30, '  ') { |opts|
  opts.banner = "Usage: virtualrb [options] DIRECTORY"
  opts.separator("")
  opts.separator("Options:")
  opts.on("--with-rubygems=[VERSION]", "set up virtualized Rubygems") { |version|
    gems = true
    gemversion = version  if version
  }
  opts.on("--with-ruby PATH", "use the Ruby binary in PATH", String) { |bin|
    ruby = bin
  }
  opts.on("--no-inherit", "don't inherit the site path from Ruby", String) { |bin|
    inherit = false
  }
 
  opts.on("-h", "--help", "Show this message") do
    puts opts
    exit
  end
 
  opts.on("-v", "--version", "Show version") do
    puts "virtualrb #{VIRTUALRB_VERSION}"
    exit
  end
 
  opts.separator("")
  opts.separator("Default ruby: #{find_ruby}")
 
  opts.parse! ARGV
}
 
root = ARGV[0] or abort opts.to_s
 
root = File.expand_path(root)
ruby = File.expand_path(ruby)
 
version = `#{ruby} -v`
cfg = Marshal.load `#{ruby} -r rbconfig -e 'Marshal.dump Config::CONFIG, STDOUT'`
 
puts "* Setting up a virtual Ruby for"
puts"    #{version}"
 
FileUtils.mkdir_p(root)
FileUtils.mkdir_p("#{root}/bin")
FileUtils.mkdir_p("#{root}/lib/site_ruby/1.8")
FileUtils.mkdir_p("#{root}/lib/gemhome")  if gems
 
File.open("#{root}/bin/ruby", "wb") { |script|
  script.write(<<EOF)
#!/bin/sh
 
if [ "`#{ruby} -v`" = #{version.chomp.dump} ]; then
  exec #{ruby} -r "#{root}/lib/site_ruby/1.8/site.rb" "$@";
else
  echo "Version mismatch.  Got '`#{ruby} -v`', required '#{version}'" >/dev/stderr
  echo "If this is intentional, refresh the virtualized root by running virtualrb again." >/dev/stderr
  exit -1
fi
EOF
}
File.chmod(0755, "#{root}/bin/ruby")
 
File.open("#{root}/bin/irb", "wb") { |script|
  script.puts "#!#{root}/bin/ruby"
  script.puts "# was:"
  script.puts File.read(File.dirname(ruby) + "/irb")
}
File.chmod(0755, "#{root}/bin/irb")
 
begin
  naive = File.read(File.join(File.dirname(__FILE__), "naive-install"))
  File.open("#{root}/bin/naive-install", "wb") { |script|
    script.puts "#!#{root}/bin/ruby -s"
    script.puts "# was:"
    script.puts naive
  }
  File.chmod(0755, "#{root}/bin/naive-install")
rescue Errno::ENOENT
end
 
File.open("#{root}/bin/activate", "wb") { |script|
  script.write(<<EOF)
#!/bin/sh
if [ -z "$PS1" ]; then
  echo "activate must be run by sourcing." >/dev/stderr
  exit -1
fi
 
if [ "$_VRB_ROOT" ]; then
  echo "Don't activate without deactivating first." >/dev/stderr
  return
fi
 
_VRB_ROOT="#{root}"
_OLD_VRB_PATH="$PATH"
_OLD_VRB_PS1="$PS1"
 
deactivate() {
  export PATH="$_OLD_VRB_PATH"
  export PS1="$_OLD_VRB_PS1"
  hash -r
  unset _VRB_ROOT
  unset -f deactivate
}
 
export PS1="(`basename "$_VRB_ROOT"`) $PS1"
export PATH="$_VRB_ROOT/bin:$PATH"
hash -r
EOF
}
File.chmod(0755, "#{root}/bin/activate")
 
File.open("#{root}/lib/site_ruby/1.8/site.rb", "wb") { |script|
  script.puts "# This file has been created by virtualrb on #{Time.now}"
  script.puts "# for #{ruby}"
  script.puts "# relocated to #{root}"
  script.puts "# #{version}"
  script.puts
  script.puts "RUBY_VIRTUALRB = true"
 
  unless inherit
    %w{sitedir sitelibdir sitearchdir}.each { |dir|
      script.puts "$LOAD_PATH.delete(#{cfg[dir].dump})"
    }
  end
 
  script.puts "$LOAD_PATH.unshift(#{"#{root}/lib/site_ruby/1.8".dump})"
  script.puts "$LOAD_PATH.unshift(#{"#{root}/lib/site_ruby/1.8/#{cfg["sitearch"]}".dump})"
 
  if gems
    script.write <<EOF
 
require 'rubygems'
 
# Virtual Rubygems should not fiddle with ~/.gemrc
def Gem.find_home
  "#{root}/lib/gemhome/"
end
EOF
  end
}
 
def patch_settings(config, values)
  values.inject(config) { |cfg, (key, value)|
    cfg.gsub(/(.*#{Regexp.escape key} = ).*/i, "\\1#{value.dump}")
  }
end
 
File.open("#{root}/lib/site_ruby/1.8/rbconfig.rb", "wb") { |script|
  script.puts "# This file has been patched by virtualrb on #{Time.now}"
  script.puts "# for #{ruby}"
  script.puts "# relocated to #{root}"
  script.puts "# #{version}"
 
  config = patch_settings(File.read(find_rbconfig(ruby)),
                          'TOPDIR' => root,
                          'CONFIG["ruby_install_name"]' => "ruby",
                          'CONFIG["sitedir"]' => root + "/lib/site_ruby",
                          'CONFIG["archdir"]' => cfg["archdir"])
 
  script.write(config.
               gsub(/.*RUBY_FRAMEWORK.*/, ''). # no special deal on OS X
               gsub(/.*APPLE_GEM_HOME.*/, '')  #      ----- " -----
               )
}
 
if gems
  begin
    require 'rubygems'
  rescue LoadError
    abort "* No Rubygems found, please install manually in the activated env."
  end
 
  begin
    gem 'rubygems-update', gemversion
  rescue LoadError
    p $!
    abort "* No appropriate rubygems-update found to install Rubygems into\n" +
      "    the virtual env, please gem install rubygems-update."
  end
 
  update_dir = $LOAD_PATH.find { |fn| fn =~ /rubygems-update/ }
 
  if update_dir.nil?
    abort "* Internal error in virtualrb, where has the rubygems-update gone?  Please file a bug."
  else
    update_dir = File.dirname(update_dir)
    Dir.chdir update_dir
    update_dir =~ /([0-9.]*)$/
    puts "* Installing RubyGems #{$1}"
    system "#{root}/bin/ruby setup.rb"
    puts "* Consider running"
    puts "    #{root}/bin/gem sources -a http://gems.github.com"
  end
end
 
puts "* virtual Ruby set up, run to enter:"
puts "    source #{root}/bin/activate"