# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with this
# work for additional information regarding copyright ownership.  The ASF
# licenses this file to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
# License for the specific language governing permissions and limitations under
# the License.


require 'benchmark'
require 'jruby'
require 'monitor'
require 'ostruct'
require 'rbconfig'
require 'thread'
require 'buildr/core/application_cli'

module Buildr

  #  See the nailgun_help method for documentation.
  module Nailgun # :nodoc:
    extend self
    
    VERSION = '0.7.1'
    NAME = "nailgun-#{VERSION}"
    URL = "http://downloads.sourceforge.net/nailgun/#{NAME}.zip"
    ARTIFACT_SPEC = "com.martiansoftware:nailgun:jar:#{VERSION}"
    BUILDR_PATHS = [File.expand_path('../', File.dirname(__FILE__)),
                    File.expand_path('../../lib', File.dirname(__FILE__))]
    
    attr_accessor :artifact
    attr_accessor :server, :port, :jruby_queue_size, :buildr_queue_size
    attr_accessor :jruby_home, :home
    
    self.jruby_home = if PLATFORM =~ /java/
                        Config::CONFIG['prefix']
                      else
                        ENV['JRUBY_HOME'] || File.join(ENV['HOME'], '.jruby')
                      end
    
    self.home = ENV['NAILGUN_HOME'] || File.join(jruby_home, 'tool', 'nailgun')
    self.server = 'localhost'
    self.port = 2113
    self.jruby_queue_size = 3
    self.buildr_queue_size = 3

    def namespace(&block)
      if Object.const_defined?(:Rake)
        Rake.application.in_namespace(:nailgun, &block)
      end
    end

    def boot(&block)
      if block
        @boot = block
      else
        @boot.call
      end
    end

    module Application
      def nailgun_help
        "  " + <<-DESC.strip.gsub(/ *\n +/, "\n  ")
          NailGun is a client, protocol, and server for running Java 
          programs from the command line without incurring the JVM
          startup overhead. Nailgun integration is currently available
          only when running Buildr with JRuby.

          Buildr provides a custom nailgun server, allowing you to 
          start a single JVM and let buildr create a queue of runtimes.
          These JRuby runtimes can be cached (indexed by buildfile path)
          and are automatically reloaded when the buildfile has been modified.
          Runtime caching allows you to execute tasks without
          spending time creating the buildr environment. Some nailgun 
          tasks have been provided to manage the cached runtimes.

          To start the buildr server execute the following task:

              nailgun:start

          Server output will display a message when it becomes ready, you
          will also see messages when the JRuby runtimes are being created,
          or when a new buildr environment is being loaded on them.
          After the runtime queues have been populated, you can start calling
          buildr as you normally do, by invoking the $NAILGUN_HOME/ng binary:

              # on another terminal, change directory to a project.
              # if this project is the same nailgun:start was invoked on, it's 
              # runtime has been cached, so no loading is performed unless 
              # the buildfile has been modified. otherwise the buildfile 
              # will be loaded on a previously loaded fresh-buildr runtime
              # and it will be cached.
              cd /some/buildr/project
              ng nailgun:help                      # display nailgun help
              ng nailgun:tasks                     # display overview of ng tasks
              ng clean compile                # just invoke those two tasks

             Configuration and Environment Variables.

          Before starting the server, buildr will check if you have 
          nailgun already installed by seeking the nailgun jar under

              $NAILGUN_HOME

          You can override this environment variable to tell buildr where
          to find or where to install nailgun. If missing, NAILGUN_HOME
          defaults to the $JRUBY_HOME/tool/nailgun directory. You can 
          also specify the nailgun_home on your buildfile with the following
          code:
              
              require 'buildr/nailgun'
              Buildr::Nailgun.home = File.expand_path('~/.jruby/tool/nailgun')

          Buildr will also check that the nailgun client binary (ng.exe for 
          Windows systems, ng otherwise) is installed on NAILGUN_HOME. 
          If no binary is found, buildr will download nailgun and 
          compile+install it.
          
          
          The buildr server binds itself to localhost, port 2113. You can 
          override this on your buildfile, by placing the following code:

              require 'buildr/nailgun'
              Buildr::Nailgun.server = '127.0.0.1'
              Buildr::Nailgun.port = 2233

          If you provided custom host/port settings you need
          to tell the nailgun client where to connect to:

              ng --nailgun-server 127.0.0.1 --nailgun-port 2233 nailgun:tasks

          The buildr server starts a BuildrFactory responsible for providing
          a pool of JRuby runtimes configured and ready for task execution. 
          This BuildrFactory consists of two queues: One of pure JRuby runtimes
          with almost nothing loaded, and another of Buildr runtimes (consumed
          from the first queue) with the Buildr runtime preloaded but without
          any project definition. The jruby queue is used for sandboxing code
          like running GetoptLong, but most importantly its the place where 
          buildr runtimes begin life, to be later added on the buildr queue.
          By default both queues are of size 3, you can customize this with:

              require 'buildr/nailgun'
              Buildr::Nailgun.jruby_queue_size = 4 # JRuby creation is fast!
              Buildr::Nailgun.buildr_queue_size = 5 # loading buildr takes longer

          The buildr_queue_size is of particular importance if you expect to 
          reload lots of buildfiles.
 
          Execute nailgun:tasks get an overview of available nailgun tasks.
          
        DESC
      end
      
      def nailgun_tasks
        tasks = {}
        tasks['nailgun:help'] = 'Display nailgun help'
        tasks['nailgun:start'] = 'Start the Nailgun server.'
        tasks['nailgun:stop'] = 'Stop the Nailgun server.'
        tasks['nailgun:tasks'] = 'Display this message'
        tasks['nailgun:list'] = <<-DESC
                 Display a list of builfile paths having an associated
                 buildr runtime. Having a cached runtime reduces buidlr
                 execution time.

                 If buildr finds the current buildfile on this list, 
                 no file loading will be performed, only execution of 
                 specified tasks on the previously loaded environment. 
                 However if the cached runtime is out of date (buildfile
                 has been modified) the runtime will be reloaded.

                 This feature becomes handy when performing development
                 cycle: edit -> compile -> test -> report. 

                 This task exits inmediatly after printing the file list.
            DESC
        tasks['nailgun:clear'] = <<-DESC
                 Remove all cached buildr runtimes and exit
            DESC
        tasks['nailgun:load'] = <<-DESC
                 Add or update a cached runtime.
                 
                 Use this task to create a cached buildr runtime for a 
                 buildfile.
            DESC
        tasks['nailgun:delete'] = <<-DESC
                 Delete cached runtime for a buildfile and exit.
            DESC
        tasks['nailgun:once [tasks]'] = <<-DESC
                 Ignore cached runtime and perform tasks on a newly 
                 created environment. This new runtime is dropped right
                 after buildr completion.
            DESC
        
        out = ""
        out << "\nNailgun tasks:\n"
        tasks.each_pair do |task, desc|
          out << "\n"
          out << sprintf("  %20-s\n", [task].flatten.join(' | '))
          out << sprintf("      %s\n", desc.strip.gsub(/ *\n +/, "\n      "))
        end
        out
      end
      
      def buildfile(dir = nil, candidates = nil)
        dir ||= Dir.pwd
        candidates ||= @rakefiles.dup
        Util.find_buildfile(dir, candidates, options.nosearch)
      end
      
      def clear_invoked
        tasks.each do |task|
          is_project = Project.instance_variable_get(:@projects).key?(task.name)
          task.instance_variable_set(:@already_invoked, false) unless is_project
        end
      end

      if Buildr.const_defined?(:Application)
        class Buildr::Application
          include Nailgun::Application
          public :requires
        end
      end
    end
    
    module ContextRunner
      extend self
      
      def parse_options(ctx, opts)
        opts.requires = []
        Buildr.const_set(:VERSION, ctx.server.runtime.object.const_get(:Buildr)::VERSION)
  
        obj = OpenStruct.new(:ctx => ctx, :opts => opts)
        class << obj
          include Buildr::CommandLineInterface
          
          def help
            super
            puts 
            puts 'To get a summary of Nailgun features use'
            puts '  nailgun:help'
          end

          def do_option(opt, value)
            case opt
            when '--help'
              help
              opts.exit = true
            when '--version'
              puts version
              opts.exit = true
            when '--environment'
              ctx.env['BUILDR_ENV'] = value
            when '--buildfile'
              opts.buildfile = value
            when '--require'
              opts.requires << value
            when '--nosearch'
              opts.nosearch = true
            end
          end
        end
        
        ARGV.replace(ctx.argv)
        obj.parse_options
      end
      
      def run(ctx)
        ARGV.replace(ctx.argv)
        Dir.chdir(ctx.pwd)
        ctx.env.each { |k, v| ENV[k.to_s] = v.to_s }
        Buildr::Application.module_eval do
          include Nailgun::Application
        end
        task 'nailgun:load' do
          puts "Buildfile #{Rake.application.buildfile} loaded"
        end
        if ctx.fresh
          run_fresh(ctx)
        else
          run_local(ctx)
        end
      end
      
      private
      
      def run_fresh(ctx)
        Project.clear
        old_app = Rake.application
        Rake.application = Buildr::Application.new
        Rake.application.instance_eval do
          @tasks = old_app.instance_variable_get(:@tasks)
          @rules = old_app.instance_variable_get(:@rules)
          run
        end
      end

      def run_local(ctx)
        Rake.application.instance_eval do
          verbose(nil)
          options.trace = false
          parse_options
          collect_tasks
          clear_invoked
          top_level_tasks.delete('buildr:initialize')
          Util.benchmark { top_level } 
        end
      end
    end

    module Util
      extend self

      def find_buildfile(pwd, candidates, nosearch=false)
        candidates = [candidates].flatten
        buildfile = candidates.find { |c| File.file?(File.expand_path(c, pwd)) }
        return File.expand_path(buildfile, pwd) if buildfile
        return nil if nosearch
        updir = File.dirname(pwd)
        return nil if File.expand_path(updir) == File.expand_path(pwd)
        find_buildfile(updir, candidates)
      end
      
      def benchmark(action = ['Completed'], verbose = true)
        result = nil
        times = Benchmark.measure do
          result = yield(action)
        end
        if verbose
          real = []
          real << ("%ih" % (times.real / 3600)) if times.real >= 3600
          real << ("%im" % ((times.real / 60) % 60)) if times.real >= 60
          real << ("%.3fs" % (times.real % 60))
          puts "#{[action].flatten.join(' ')} in #{real.join}"
        end
        result
      end

      def on_runtime(runtime, *args, &block)
        raise_error = lambda do |cls, msg, trace|
          raise RuntimeError.new(cls + ": "+ msg.to_s).tap { |e| e.set_backtrace(trace.map(&:to_s)) }
        end
        executor = runtime.object.const_get(:Module).new do
          extend self
          def runtime_exec(*args, &prc)
            define_method(:runtime_exec, &prc)
            runtime_exec(*args)
          rescue => e
            [:error, e.class.name, e.message, e.backtrace]
          end
        end
        result = executor.runtime_exec(*args, &block)
        raise_error.call(*result[1..-1]) if result.kind_of?(Array) && result.first == :error
        result
      end
    end # module Util

    boot do
      
      class ::ConcreteJavaProxy
        def self.jclass(name = nil)
          name ||= self.java_class.name
          Nailgun::Util.class_for_name(name)
        end
        
        def self.jnew(*args)
          objs = []
          classes = args.map do |a|
            case a
            when nil
              obj << nil
              nil
            when Hash
              objs << a.keys.first
              cls = a.values.first
              cls = Nailgun::Util.proxy_class(cls) if String == cls
              cls
            else
              objs << a
              a.java_class
            end
          end
          classes = classes.to_java(java.lang.Class)
          ctor = jclass.getDeclaredConstructor(classes)
          ctor.setAccessible(true)
          ctor.newInstance(objs.to_java(java.lang.Object))
        end
      end

      module Util
        def class_for_name(name)
          java.lang.Class.forName(name)
        end
        
        def add_to_sysloader(path)
          sysloader = java.lang.ClassLoader.system_class_loader
          add_url_method = class_for_name('java.net.URLClassLoader').
            getDeclaredMethod('addURL', [java.net.URL].to_java(java.lang.Class))
          add_url_method.accessible = true
          add_url_method.invoke(sysloader, [java.io.File.new(path.to_s).
                                            toURL].to_java(java.net.URL))
        end
        add_to_sysloader Nailgun.artifact
        
        def proxy_class(name)
          JavaUtilities.get_proxy_class(name)
        end

        import org.jruby.RubyIO 
        def set_stdio(runtime, dev)
          set_global = lambda do |global, constant, stream|
            runtime.global_variables.set(global, stream)
            runtime.object.send(:remove_const, constant)
            runtime.object.send(:const_set, constant, stream)
          end
          stdin  = runtime.global_variables.get('$stdin')
          stdout = runtime.global_variables.get('$stdout')
          stderr = runtime.global_variables.get('$stderr')
          input  = RubyIO.jnew(runtime, dev.in => java.io.InputStream)
          output = RubyIO.jnew(runtime, dev.out => java.io.OutputStream)
          error = RubyIO.jnew(runtime, dev.err => java.io.OutputStream)
          # stdin.reopen(input, 'r') # not working on jruby, :(
          set_global.call('$stdin', 'STDIN', input)
          stdout.reopen(output, 'w')
          stderr.reopen(error, 'w')
        end

        def redirect_stdio(runtime, nail)
          result = nil
          begin 
            set_stdio(runtime, nail)
            result = yield
          ensure
            set_stdio(runtime, java.lang.System)
          end
          result
        end
      end

      class Buildfile
        attr_reader :path, :requires, :loaded_time
        attr_accessor :runtime
        
        def initialize(path, *requires)
          @path = File.expand_path(path)
          @requires = requires.dup
        end

        def loaded!
          @loaded_time = Time.now
        end

        def last_modification
          File.timestamp(path)
        end
        
        def should_be_loaded?
          (loaded_time || Rake::EARLY) < last_modification
        end
        
        def to_s
          buff = path.dup
          buff << sprintf("\n  %-25s %s", "Last Modified:", last_modification)
          unless requires.empty?
            buff << sprintf("\n  %-25s %s", "Requires:", requires.join(" ")) 
          end
          if should_be_loaded?
            buff << sprintf("\n  %-25s %s", "Needs reload, last was:", loaded_time)
          else
            buff << sprintf("\n  %-25s %s", "Loaded at:", loaded_time)
          end
          buff << sprintf("\n  %-25s %s", "Runtime:", runtime)
          buff
        end        
      end
      
      class BuildrNail 
        include org.apache.buildr.BuildrNail
        Main = Util.proxy_class 'org.apache.buildr.BuildrNail$Main'

        attr_reader :buildfile
        
        def initialize
          buildfile = Buildfile.new(Rake.application.buildfile,
                                    *Rake.application.requires)
          buildfile.loaded!
          buildfile.runtime = JRuby.runtime
          @buildfiles = { buildfile.path => buildfile }
        end

        def main(nail)
          Thread.exclusive { Thread.current.priority = 100; run(nail) }
        end

        private
        def run(nail)
          nail.assert_loopback_client
          nail.out.println "Using #{nail.getNGServer}"
          ctx = context_from_nail(nail)
          
          case ctx.action
          when :start
            nail.out.println "Cannot start nailgun when running as client"
            return nail.exit(0)
          when :stop
            puts "Stopping #{nail.getNGServer}"
            nail.out.println "Stopping #{nail.getNGServer}"
            return nail.getNGServer.shutdown(true)
          when :list
            if @buildfiles.empty?
              nail.out.println "No defined runtimes"
            else
              nail.out.println "Defined runtimes:"
              @buildfiles.each_value { |f| nail.out.println "- #{f}" }
            end
            return nail.exit(0)
          when :clear
            @buildfiles.clear
            nail.out.println "Cleared all runtimes"
            return nail.exit(0)
          when :tasks
            nail.out.println ""
            nail.out.println Rake.application.nailgun_tasks
            return nail.exit(0)
          when :help
            nail.out.println ""
            nail.out.println Rake.application.nailgun_help
            return nail.exit(0)
          end
          
          opts = OpenStruct.new
          
          runtime = ctx.runtime
          #Util.set_stdio(runtime, nail)
          runtime.object.const_get(:Buildr)::Nailgun::ContextRunner.parse_options(ctx, opts)
          return nail.exit(0) if opts.exit

          candidates = Buildr::Application::DEFAULT_BUILDFILES
          candidates = [opts.buildfile] if opts.buildfile
          
          path = Util.find_buildfile(ctx.pwd, candidates, opts.nosearch) ||
            File.expand_path(candidates.first, ctx.pwd)
          
          if ctx.action == :delete
            nail.out.println "Deleting runtime for #{path}"
            @buildfiles.delete(path)
            return nail.exit(0)
          end

          puts "Getting buildr runtime for #{path}"
          buildfile = @buildfiles[path] || Buildfile.new(path, *opts.requires)
          
          save = buildfile.should_be_loaded? || ctx.action == :load
          
          runtime = buildfile.runtime

          if save || ctx.action == :once
            ctx.argv.unshift 'nailgun:load'
            ctx.fresh = true
            runtime = ctx.buildr
            if save
              buildfile.runtime = runtime
              buildfile.loaded!
              @buildfiles[buildfile.path] = buildfile
            end
          end

          Util.redirect_stdio(runtime, nail) do
            runtime.object.send :puts
            runtime.object.const_get(:Buildr)::Nailgun::ContextRunner.run(ctx)
          end
        end
        
        def context_from_nail(nail)
          ctx = OpenStruct.new
          ctx.pwd = nail.getWorkingDirectory
          ctx.env = nail.env
          ctx.argv = [nail.command] + nail.args.map(&:to_s)
          ctx.server = nail.getNGServer
          def ctx.runtime; @runtime ||= server.buildr_factory.runtime; end
          def ctx.buildr; @buildr ||= server.buildr_factory.obtain; end
          actions = {
            :load   => %w{ nailgun:load },
            :delete => %w{ nailgun:delete },
            :clear  => %w{ nailgun:clear },
            :list   => %w{ nailgun:list },
            :start  => %w{ nailgun:boot nailgun:start },
            :stop   => %w{ nailgun:stop },
            :once   => %w{ nailgun:once },
            :tasks  => %w{ nailgun:tasks },
            :help   => %w{ nailgun:help help:nailgun },
          }
          action = actions.find { |k,v| k if v.any? { |t| ctx.argv.delete(t) } }
          ctx.action = action.first if action
          ctx
        end
        
      end # class BuildrNail

      class BuildrFactory
        
        attr_accessor :buildrs_size, :runtimes_size
        
        def initialize(buildrs_size = 1, runtimes_size = nil)
          runtimes_size ||= buildrs_size
          @buildrs_size = buildrs_size < 1 ? 1 : buildrs_size
          @runtimes_size = runtimes_size < 1 ? 1 : runtimes_size

          @buildrs = [].extend(MonitorMixin)
          @buildrs_ready = @buildrs.new_cond
          @buildrs_needed = @buildrs.new_cond
                    
          @buildrs_creators = [].extend(MonitorMixin)

          @runtimes = [].extend(MonitorMixin)
          @runtimes_ready = @runtimes.new_cond
          @runtimes_needed = @runtimes.new_cond
          
          @runtimes_creators = [].extend(MonitorMixin)
        end
        
        def obtain
          get(:buildr)
        end

        def runtime
          get(:runtime)
        end

        def start
          debug "Starting Buildr runtime factory"
          @runtime_creator = Thread.new { loop { create :runtime } }
          @runtime_creator.priority = -2
          @buildr_creator = Thread.new { loop { create :buildr } }
          @buildr_creator.priority = 1
        end

        def stop
          @buildr_creator.kill if @buildr_creator
          @runtime_creator.kill if @runtime_creator
        end

        private
        def debug(*msg)
          puts *msg if Rake.application.options.trace
        end

        def get(thing)
          collection = instance_variable_get("@#{thing}s")
          needs = instance_variable_get("@#{thing}s_needed")
          ready = instance_variable_get("@#{thing}s_ready")
          result = nil
          collection.synchronize do 
            if collection.empty?
              debug "no #{thing} available, ask to create more"
              needs.broadcast
              debug "should be creating #{thing}"
              ready.wait_while { collection.empty? }
            end
            debug "Getting my #{thing}"
            result = collection.shift
            debug "would need more #{thing}s"
            needs.broadcast
            debug "got my #{thing}: #{result.inspect}"
            Thread.pass
          end
          debug "returning #{result.inspect}"
          result
        end

        def create(thing, *args, &prc)
          creator = needed(thing)
          collection = instance_variable_get("@#{thing}s")
          ready = instance_variable_get("@#{thing}s_ready")
          needs = instance_variable_get("@#{thing}s_needed")
          unless creator
            collection.synchronize do
              debug "awake those wanting a #{thing}"
              ready.broadcast
              Thread.pass
              debug "wait until more #{thing}s are needed"
              # needs.wait(1); return
              needs.wait_until { creator = needed(thing) }
            end
          end
          debug "About to create #{thing} # #{creator}"
          method = "create_#{thing}"
          creators = instance_variable_get("@#{thing}s_creators")
          debug "registering creator for #{thing} #{creator}"
          creators.synchronize { creators << creator }
          result = send(method, creator, *args, &prc)
          debug "created #{thing}[#{creator}] => #{result.inspect}"
          creators.synchronize do 
            debug "unregistering creator for #{thing} #{creator}"
            creators.delete(creator)
            collection.synchronize do
              debug "adding object on queue for #{thing} #{creator}"
              collection << result
            end
          end
        rescue => e
          puts "#{e.backtrace.shift}: #{e.message}"
          e.backtrace.each { |i| puts "\tfrom #{i}" }
        end
        
        def needed(thing)
          collection = instance_variable_get("@#{thing}s")
          creators = instance_variable_get("@#{thing}s_creators")
          size = instance_variable_get("@#{thing}s_size")
          collection.synchronize do
            count = collection.size
            if count < size
              count += creators.synchronize { creators.size }
            end
            count if count < size
          end
        end

        def create_runtime(creator)
          debug "Creating runtime[#{creator}]"
          Util.benchmark do |header|
            runtime = org.jruby.Ruby.newInstance
            runtime.global_variables.set('$nailgun_server', JRuby.reference($nailgun_server))
            BUILDR_PATHS.each { |path| runtime.load_service.load_path.unshift path }
            runtime.load_service.require 'buildr/nailgun'
            header.replace ["Created runtime[#{creator}]", runtime]
            runtime
          end
        end

        def create_buildr(creator)
          debug "Obtaining runtime to load buildr[#{creator}] on it"
          runtime = get(:runtime)
          debug "Loading buildr[#{creator}] on #{runtime} ..."
          Util.benchmark ["Loaded buildr[#{creator}] on #{runtime}"] do
            load_service = runtime.load_service
            load_service.require 'rubygems'
            load_service.require 'buildr'
          end
          runtime
        end
        
      end # BuildrFactory
      
      class BuildrServer < com.martiansoftware.nailgun.NGServer
        
        attr_reader :buildr_factory

        def initialize(host = 'localhost', port = 2113, buildr_factory = nil)
          super(java.net.InetAddress.get_by_name(host), port)
          @buildr_factory = buildr_factory
          @host, @port = host, port
        end

        def runtime
          JRuby.runtime
        end

        def start_server
          self.allow_nails_by_class_name = false

          BuildrNail::Main.nail = BuildrNail.new
          self.default_nail_class = BuildrNail::Main
          buildr_factory.start
          
          @thread = java.lang.Thread.new(self)
          @thread.setName(to_s)
          @thread.start
          
          sleep 1 while getPort == 0
          puts "#{self} Started."
        end

        def stop_server
          buildr_factory.stop
          @thread.kill
        end

        def to_s
          "BuildrServer(" <<
            [Rake.application.version, @host, @port].join(", ") <<
            ")"
        end
      end # class BuildrServer

    end # Nailgun boot
    
    namespace do
      tmp = lambda { |*files| File.join(Dir.tmpdir, "nailgun", *files) }
      dist_zip = Buildr.download(tmp[NAME + ".zip"] => URL)
      dist_dir = Buildr.unzip(tmp[NAME] => dist_zip)
      
      if File.exist?(File.join(home, NAME + ".jar"))
        ng_jar = file(File.join(home, NAME + ".jar"))
      else
        ng_jar = file(tmp[NAME, NAME, NAME+".jar"] => dist_dir)
      end
      
      self.artifact = Buildr.artifact(ARTIFACT_SPEC).from(ng_jar)
      
      compiled_bin = tmp[NAME, NAME, "ng"+Config::CONFIG['EXEEXT']]
      compiled_bin = file(compiled_bin => dist_dir.target) do |task|
        unless task.to_s.pathmap('%x') == '.exe'
          Dir.chdir(task.to_s.pathmap('%d')) do
            puts "Compiling #{task.to_s}"
            system('make', task.to_s.pathmap('%f')) or
              fail "Nailgun binary compilation failed."
          end
        end
      end

      installed_bin = file(File.join(home, 
          compiled_bin.to_s.pathmap('%f')) => compiled_bin) do |task|
        mkpath task.to_s.pathmap('%d'), :verbose => false
        cp compiled_bin.to_s, task.to_s, :verbose => false
      end

      task :boot => artifact do |task|
        if $nailgun_server
          raise "Already nunning on Nailgun server: #{$nailgun_server}"
        end
        tasks = Rake.application.instance_eval { @top_level_tasks.dup }
        tasks.delete_if do |t| 
          t =~ /^(buildr:initialize|(ng|nailgun):.+)$/
        end
        unless tasks.empty?
          raise "Don't specify more targets when starting Nailgun server"
        end
        boot
      end
      
      task :start => [installed_bin, :boot] do
        factory = BuildrFactory.new(buildr_queue_size, jruby_queue_size)
        $nailgun_server = BuildrServer.new(server, port, factory)
        puts "Starting #{$nailgun_server}"
        $nailgun_server.start_server

        is_win = Buildr::Util.win_os?
        bin_path = File.expand_path(installed_bin.to_s.pathmap("%d"))
        bin_name = installed_bin.to_s.pathmap("%f")

        puts <<-NOTICE

        Buildr server has been started, you may need to update your PATH
        variable in order to execute the #{bin_name} binary.

          #{ is_win ?
             "> set NAILGUN_HOME=#{bin_path}" :
             "$ export NAILGUN_HOME=#{bin_path}"
           }
          #{ is_win ?
             "> set PATH=%NAILGUN_HOME%;%PATH%" :
             "$ export PATH=${NAILGUN_HOME}:${PATH}"
           }
           
        Runtime for #{Rake.application.buildfile} has been cached, this 
        means you can open a terminal inside 

              #{Rake.application.buildfile.pathmap("%d")}

        Invoke tasks by executing the #{bin_name} program, it takes the
        same parameters you normally use for ``buildr''. 

        To display Nailgun related help, execute the command:
            ``#{bin_name} nailgun:help''

        To get an overview of Nailgun tasks, execute the command:
            ``#{bin_name} nailgun:tasks''

        NOTICE
      end

      task :help do 
        puts Rake.application.nailgun_help
      end

      task :tasks do 
        puts Rake.application.nailgun_tasks
      end
      
    end # namespace :nailgun
    
  end # module Nailgun

end