require 'pathname'
require 'rubygems'
Gem.source_index # ensure Rubygems is fully loaded in Ruby 1.9

module Gem
  class Dependency
    if !instance_methods.map { |m| m.to_s }.include?("requirement")
      def requirement
        version_requirements
      end
    end
  end
end

module Bundler
  class Specification < Gem::Specification
    attr_accessor :relative_loaded_from

    def self.from_gemspec(gemspec)
      spec = allocate
      gemspec.instance_variables.each do |ivar|
        spec.instance_variable_set(ivar, gemspec.instance_variable_get(ivar))
      end
      spec
    end

    def loaded_from
      return super unless relative_loaded_from
      source.path.join(relative_loaded_from).to_s
    end

    def full_gem_path
      Pathname.new(loaded_from).dirname.expand_path.to_s
    end
  end

  module SharedHelpers
    attr_accessor :gem_loaded

    def default_gemfile
      gemfile = find_gemfile
      gemfile or raise GemfileNotFound, "Could not locate Gemfile"
      Pathname.new(gemfile)
    end

    def in_bundle?
      find_gemfile
    end

  private

    def find_gemfile
      return ENV['BUNDLE_GEMFILE'] if ENV['BUNDLE_GEMFILE']

      previous = nil
      current  = File.expand_path(Dir.pwd)

      until !File.directory?(current) || current == previous
        filename = File.join(current, 'Gemfile')
        return filename if File.file?(filename)
        current, previous = File.expand_path("..", current), current
      end
    end

    def clean_load_path
      # handle 1.9 where system gems are always on the load path
      if defined?(::Gem)
        me = File.expand_path("../../", __FILE__)
        $LOAD_PATH.reject! do |p|
          next if File.expand_path(p).include?(me)
          p != File.dirname(__FILE__) &&
            Gem.path.any? { |gp| p.include?(gp) }
        end
        $LOAD_PATH.uniq!
      end
    end

    def reverse_rubygems_kernel_mixin
      # Disable rubygems' gem activation system
      ::Kernel.class_eval do
        if private_method_defined?(:gem_original_require)
          alias rubygems_require require
          alias require gem_original_require
        end

        undef gem
      end
    end

    def cripple_rubygems(specs)
      reverse_rubygems_kernel_mixin

      executables = specs.map { |s| s.executables }.flatten
      Gem.source_index # ensure RubyGems is fully loaded

     ::Kernel.class_eval do
        private
        def gem(*) ; end
      end

      ::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

        gem_bin = File.join(spec.full_gem_path, spec.bindir, exec_name)
        gem_from_path_bin = File.join(File.dirname(spec.loaded_from), spec.bindir, exec_name)
        File.exist?(gem_bin) ? gem_bin : gem_from_path_bin
      end

      Gem.clear_paths
    end

    extend self
  end
end