class Bundler::Standalone

def bundler_path
  Bundler.root.join(Bundler.settings[:path].to_s, "bundler")
end

def define_path_helpers
  <<~'END'
    unless defined?(Gem)
      module Gem
        def self.ruby_api_version
          RbConfig::CONFIG["ruby_version"]
        end
        def self.extension_api_version
          if 'no' == RbConfig::CONFIG['ENABLE_SHARED']
            "#{ruby_api_version}-static"
          else
            ruby_api_version
          end
        end
      end
    end
  END
end

def extensions_dir
  %r{extensions/(?<platform>[^/]+)/#{Regexp.escape(Gem.extension_api_version)}}
end

def gem_path(path, spec)
  full_path = Pathname.new(path).absolute? ? path : File.join(spec.full_gem_path, path)
  if spec.source.instance_of?(Source::Path)
    full_path
  else
    Pathname.new(full_path).relative_path_from(Bundler.root.join(bundler_path)).to_s
  end
rescue TypeError
  error_message = "#{spec.name} #{spec.version} has an invalid gemspec"
  raise Gem::InvalidSpecificationException.new(error_message)
end

def generate
  SharedHelpers.filesystem_access(bundler_path) do |p|
    FileUtils.mkdir_p(p)
  end
  File.open File.join(bundler_path, "setup.rb"), "w" do |file|
    file.puts "require 'rbconfig'"
    file.puts define_path_helpers
    file.puts reverse_rubygems_kernel_mixin
    paths.each do |path|
      if Pathname.new(path).absolute?
        file.puts %($:.unshift "#{path}")
      else
        file.puts %($:.unshift File.expand_path("\#{__dir__}/#{path}"))
      end
    end
  end
end

def initialize(groups, definition)
  @specs = definition.specs_for(groups)
end

def paths
  @specs.map do |spec|
    next if spec.name == "bundler"
    Array(spec.require_paths).map do |path|
      gem_path(path, spec).
        sub(version_dir, '#{RUBY_ENGINE}/#{Gem.ruby_api_version}').
        sub(extensions_dir, 'extensions/\k<platform>/#{Gem.extension_api_version}')
      # This is a static string intentionally. It's interpolated at a later time.
    end
  end.flatten.compact
end

def reverse_rubygems_kernel_mixin
  <<~END
  kernel = (class << ::Kernel; self; end)
  [kernel, ::Kernel].each do |k|
    if k.private_method_defined?(:gem_original_require)
      private_require = k.private_method_defined?(:require)
      k.send(:remove_method, :require)
      k.send(:define_method, :require, k.instance_method(:gem_original_require))
      k.send(:private, :require) if private_require
    end
  end
  END
end

def version_dir
  "#{RUBY_ENGINE}/#{Gem.ruby_api_version}"
end