#
#   shell/process-controller.rb -
#   	$Release Version: 0.7 $
#   	$Revision$
#   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
#
# --
#
#
#
require "forwardable"

require "thread"
require "sync"

class Shell
  class ProcessController

    @ProcessControllers = {}
    @ProcessControllersMonitor = Mutex.new
    @ProcessControllersCV = ConditionVariable.new

    @BlockOutputMonitor = Mutex.new
    @BlockOutputCV = ConditionVariable.new

    class<<self
      extend Forwardable

      def_delegator("@ProcessControllersMonitor",
		    "synchronize", "process_controllers_exclusive")

      def active_process_controllers
	process_controllers_exclusive do
	  @ProcessControllers.dup
	end
      end

      def activate(pc)
	process_controllers_exclusive do
	  @ProcessControllers[pc] ||= 0
	  @ProcessControllers[pc] += 1
	end
      end

      def inactivate(pc)
	process_controllers_exclusive do
	  if @ProcessControllers[pc]
	    if (@ProcessControllers[pc] -= 1) == 0
	      @ProcessControllers.delete(pc)
	      @ProcessControllersCV.signal
	    end
	  end
	end
      end

      def each_active_object
	process_controllers_exclusive do
	  for ref in @ProcessControllers.keys
	    yield ref
	  end
	end
      end

      def block_output_synchronize(&b)
	@BlockOutputMonitor.synchronize(&b)
      end

      def wait_to_finish_all_process_controllers
	process_controllers_exclusive do
	  while !@ProcessControllers.empty?
	    Shell::notify("Process finishing, but active shell exists",
			  "You can use Shell#transact or Shell#check_point for more safe execution.")
	    if Shell.debug?
	      for pc in @ProcessControllers.keys
		Shell::notify(" Not finished jobs in "+pc.shell.to_s)
 		for com in pc.jobs
 		  com.notify("  Jobs: %id")
 		end
	      end
	    end
	    @ProcessControllersCV.wait(@ProcessControllersMonitor)
	  end
	end
      end
    end

    # for shell-command complete finish at this process exit.
    USING_AT_EXIT_WHEN_PROCESS_EXIT = true
    at_exit do
      wait_to_finish_all_process_controllers unless $@
    end

    def initialize(shell)
      @shell = shell
      @waiting_jobs = []
      @active_jobs = []
      @jobs_sync = Sync.new

      @job_monitor = Mutex.new
      @job_condition = ConditionVariable.new
    end

    attr_reader :shell

    def jobs
      jobs = []
      @jobs_sync.synchronize(:SH) do
	jobs.concat @waiting_jobs
	jobs.concat @active_jobs
      end
      jobs
    end

    def active_jobs
      @active_jobs
    end

    def waiting_jobs
      @waiting_jobs
    end

    def jobs_exist?
      @jobs_sync.synchronize(:SH) do
	@active_jobs.empty? or @waiting_jobs.empty?
      end
    end

    def active_jobs_exist?
      @jobs_sync.synchronize(:SH) do
	@active_jobs.empty?
      end
    end

    def waiting_jobs_exist?
      @jobs_sync.synchronize(:SH) do
	@waiting_jobs.empty?
      end
    end

    # schedule a command
    def add_schedule(command)
      @jobs_sync.synchronize(:EX) do
	ProcessController.activate(self)
	if @active_jobs.empty?
	  start_job command
	else
	  @waiting_jobs.push(command)
	end
      end
    end

    # start a job
    def start_job(command = nil)
      @jobs_sync.synchronize(:EX) do
	if command
	  return if command.active?
	  @waiting_jobs.delete command
	else
	  command = @waiting_jobs.shift
#	  command.notify "job(%id) pre-start.", @shell.debug?

	  return unless command
	end
	@active_jobs.push command
	command.start
#	command.notify "job(%id) post-start.", @shell.debug?

	# start all jobs that input from the job
	for job in @waiting_jobs.dup
	  start_job(job) if job.input == command
	end
#	command.notify "job(%id) post2-start.", @shell.debug?
      end
    end

    def waiting_job?(job)
      @jobs_sync.synchronize(:SH) do
	@waiting_jobs.include?(job)
      end
    end

    def active_job?(job)
      @jobs_sync.synchronize(:SH) do
	@active_jobs.include?(job)
      end
    end

    # terminate a job
    def terminate_job(command)
      @jobs_sync.synchronize(:EX) do
	@active_jobs.delete command
	ProcessController.inactivate(self)
	if @active_jobs.empty?
	  command.notify("start_job in terminate_job(%id)", Shell::debug?)
	  start_job
	end
      end
    end

    # kill a job
    def kill_job(sig, command)
      @jobs_sync.synchronize(:EX) do
	if @waiting_jobs.delete command
	  ProcessController.inactivate(self)
	  return
	elsif @active_jobs.include?(command)
	  begin
	    r = command.kill(sig)
	    ProcessController.inactivate(self)
	  rescue
	    print "Shell: Warn: $!\n" if @shell.verbose?
	    return nil
	  end
	  @active_jobs.delete command
	  r
	end
      end
    end

    # wait for all jobs to terminate
    def wait_all_jobs_execution
      @job_monitor.synchronize do
	begin
	  while !jobs.empty?
	    @job_condition.wait(@job_monitor)
	    for job in jobs
	      job.notify("waiting job(%id)", Shell::debug?)
	    end
	  end
	ensure
	  redo unless jobs.empty?
	end
      end
    end

    # simple fork
    def sfork(command, &block)
      pipe_me_in, pipe_peer_out = IO.pipe
      pipe_peer_in, pipe_me_out = IO.pipe


      pid = nil
      pid_mutex = Mutex.new
      pid_cv = ConditionVariable.new

      Thread.start do
	ProcessController.block_output_synchronize do
	  STDOUT.flush
	  ProcessController.each_active_object do |pc|
	    for jobs in pc.active_jobs
	      jobs.flush
	    end
	  end

	  pid = fork {
	    Thread.list.each do |th|
#	      th.kill unless [Thread.main, Thread.current].include?(th)
	      th.kill unless Thread.current == th
	    end

	    STDIN.reopen(pipe_peer_in)
	    STDOUT.reopen(pipe_peer_out)

	    ObjectSpace.each_object(IO) do |io|
	      if ![STDIN, STDOUT, STDERR].include?(io)
		io.close unless io.closed?
	      end
	    end

	    yield
	  }
	end
	pid_cv.signal

	pipe_peer_in.close
	pipe_peer_out.close
	command.notify "job(%name:##{pid}) start", @shell.debug?

	begin
	  _pid = nil
	  command.notify("job(%id) start to waiting finish.", @shell.debug?)
	  _pid = Process.waitpid(pid, nil)
	rescue Errno::ECHILD
	  command.notify "warn: job(%id) was done already waitpid."
	  _pid = true
	  #	rescue
	  #	  STDERR.puts $!
	ensure
	  command.notify("Job(%id): Wait to finish when Process finished.", @shell.debug?)
	  # when the process ends, wait until the command terminates
	  if USING_AT_EXIT_WHEN_PROCESS_EXIT or _pid
	  else
	    command.notify("notice: Process finishing...",
			   "wait for Job[%id] to finish.",
			   "You can use Shell#transact or Shell#check_point for more safe execution.")
	    redo
	  end

#	  command.notify "job(%id) pre-pre-finish.", @shell.debug?
	  @job_monitor.synchronize do
#	    command.notify "job(%id) pre-finish.", @shell.debug?
	    terminate_job(command)
#	    command.notify "job(%id) pre-finish2.", @shell.debug?
	    @job_condition.signal
	    command.notify "job(%id) finish.", @shell.debug?
	  end
	end
      end

      pid_mutex.synchronize do
	while !pid
	  pid_cv.wait(pid_mutex)
	end
      end

      return pid, pipe_me_in, pipe_me_out
    end
  end
end