module Bundler::SharedHelpers

def cripple_rubygems(specs)
  reverse_rubygems_kernel_mixin
  executables = specs.map { |s| s.executables }.flatten
 :: Kernel.class_eval do
    private
    def gem(*) ; end
  end
  Gem.source_index # ensure RubyGems is fully loaded
  ::Kernel.send(:define_method, :gem) do |dep, *reqs|
    if executables.include? File.basename(caller.first.split(':').first)
      return
    end
    opts = reqs.last.is_a?(Hash) ? reqs.pop : {}
    unless dep.respond_to?(:name) && dep.respond_to?(:requirement)
      dep = Gem::Dependency.new(dep, reqs)
    end
    spec = specs.find  { |s| s.name == dep.name }
    if spec.nil?
      e = Gem::LoadError.new "#{dep.name} is not part of the bundle. Add it to Gemfile."
      e.name = dep.name
      e.version_requirement = dep.requirement
      raise e
    elsif dep !~ spec
      e = Gem::LoadError.new "can't activate #{dep}, already activated #{spec.full_name}. " \
                             "Make sure all dependencies are added to Gemfile."
      e.name = dep.name
      e.version_requirement = dep.requirement
      raise e
    end
    true
  end
  # === Following hacks are to improve on the generated bin wrappers ===
  # Yeah, talk about a hack
  source_index_class = (class << Gem::SourceIndex ; self ; end)
  source_index_class.send(:define_method, :from_gems_in) do |*args|
    source_index = Gem::SourceIndex.new
    source_index.spec_dirs = *args
    source_index.add_specs(*specs)
    source_index
  end
  # OMG more hacks
  gem_class = (class << Gem ; self ; end)
  gem_class.send(:define_method, :bin_path) do |name, *args|
    exec_name, *reqs = args
    spec = nil
    if exec_name
      spec = specs.find { |s| s.executables.include?(exec_name) }
      spec or raise Gem::Exception, "can't find executable #{exec_name}"
    else
      spec = specs.find  { |s| s.name == name }
      exec_name = spec.default_executable or raise Gem::Exception, "no default executable for #{spec.full_name}"
    end
    File.join(spec.full_gem_path, spec.bindir, exec_name)
  end
end