class Selenium::WebDriver::ChildProcess

def self.build(*command)
  new(*command)
end

def alive?
  @pid && !exited?
end

def exited?
  return false unless @pid
  WebDriver.logger.debug("Checking if #{@pid} is exited:", id: :process)
  _, @status = waitpid2(@pid, Process::WNOHANG | Process::WUNTRACED) if @status.nil?
  return false if @status.nil?
  exit_code = @status.exitstatus || @status.termsig
  WebDriver.logger.debug("  -> exit code is #{exit_code.inspect}", id: :process)
  !!exit_code
rescue Errno::ECHILD, Errno::ESRCH
  WebDriver.logger.debug("  -> process: #{@pid} already finished", id: :process)
  true
end

def initialize(*command)
  @command = command
  @detach = false
  @pid = nil
  @status = nil
end

def io
  @io ||= Platform.null_device
end

def kill(pid)
  Process.kill(SIGKILL, pid)
end

def poll_for_exit(timeout)
  WebDriver.logger.debug("Polling #{timeout} seconds for exit of #{@pid}", id: :process)
  end_time = Time.now + timeout
  sleep POLL_INTERVAL until exited? || Time.now > end_time
  raise TimeoutError, "  ->  #{@pid} still alive after #{timeout} seconds" unless exited?
end

def start
  options = {%i[out err] => io}
  options[:pgroup] = true unless Platform.windows? # NOTE: this is a bug only in Windows 7
  WebDriver.logger.debug("Starting process: #{@command} with #{options}", id: :process)
  @pid = Process.spawn(*@command, options)
  WebDriver.logger.debug("  -> pid: #{@pid}", id: :process)
  Process.detach(@pid) if detach
end

def stop(timeout = 3)
  return unless @pid
  return if exited?
  terminate_and_wait_else_kill(timeout)
rescue Errno::ECHILD, Errno::ESRCH => e
  # Process exited earlier than terminate/kill could catch
  WebDriver.logger.debug("    -> process: #{@pid} does not exist (#{e.class.name})", id: :process)
end

def terminate(pid)
  Process.kill(SIGTERM, pid)
end

def terminate_and_wait_else_kill(timeout)
  WebDriver.logger.debug("Sending TERM to process: #{@pid}", id: :process)
  terminate(@pid)
  poll_for_exit(timeout)
  WebDriver.logger.debug("  -> stopped #{@pid}", id: :process)
rescue TimeoutError, Errno::EINVAL
  WebDriver.logger.debug("    -> sending KILL to process: #{@pid}", id: :process)
  kill(@pid)
  wait
  WebDriver.logger.debug("      -> killed #{@pid}", id: :process)
end

def wait
  return if exited?
  _, @status = waitpid2(@pid)
end

def waitpid2(pid, flags = 0)
  Process.waitpid2(pid, flags)
end