module MiGA::Common::WithDaemon

def active?
  return false unless File.exist? alive_file
  (last_alive || Time.new(0)) > Time.now - 60
end

def alive_file
  self.class.alive_file(daemon_home)
end

def daemon(task, opts = [], wait = true)
  MiGA::MiGA.DEBUG "#{self.class}#daemon #{task} #{opts}"
  task = task.to_sym
  raise "Unsupported task: #{task}" unless respond_to? task
  return send(task, opts, wait) unless %i[start run].include? task
  # start & run:
  options = default_options
  opts.unshift(task.to_s)
  options[:ARGV] = opts
  # This additional degree of separation below was introduced so the Daemons
  # package doesn't kill the parent process in workflows.
  pid = fork { launch_daemon_proc(options) }
  Process.wait(pid) if wait
  pid
end

def declare_alive
  if active?
    raise "Trying to declare alive an active daemon, if you think this is a" \
      " mistake please remove #{alive_file} or try again in 1 minute"
  end
  @declare_alive_pid = fork { declare_alive_loop }
  sleep(1) # <- to wait for the process check
end

def declare_alive_loop(pid = Process.ppid)
  i = -1
  loop do
    i += 1
    return :no_home unless Dir.exist? daemon_home
    return :no_process_alive unless process_alive? pid
    write_alive_file if i % 30 == 0
    return :termination_file if termination_file? pid
    sleep(1)
  end
end

def default_options
  {
    dir_mode: :normal, dir: daemon_home, multiple: false, log_output: true,
    stop_proc: :terminate
  }
end

def in_loop
  if loop_i.nil?
    declare_alive
    daemon_first_loop
    @loop_i = -1
  end
  @loop_i += 1
  daemon_loop
end

def last_alive
  self.class.last_alive(daemon_home)
end

def launch_daemon_proc(options)
  Daemons.run_proc("#{daemon_name}", options) { while in_loop; end }
end

def output_file
  File.join(daemon_home, "#{daemon_name}.output")
end

def pid_file
  File.join(daemon_home, "#{daemon_name}.pid")
end

def process_alive?(pid)
  Process.kill(0, pid)
  true
rescue Errno::ESRCH, Errno::EPERM, Errno::ENOENT
  terminate
  false
end

def run(opts = [], wait = true)
  daemon(:run, opts, wait)
end

def start(opts = [], wait = true)
  daemon(:start, opts, wait)
end

def status(opts = [], wait = true)
  if active?
    say "Running with pid #{File.size?(pid_file) ? File.read(pid_file) : '?'}"
  else
    say 'Not running'
  end
end

def stop(opts = [], wait = true)
  if active?
    say 'Sending termination message'
    FileUtils.touch(terminate_file)
    sleep(0.5) while active? if wait
    File.unlink(pid_file) if File.exist?(pid_file)
  else
    say 'No running instances'
  end
end

def terminate
  unless declare_alive_pid.nil?
    Process.kill(9, declare_alive_pid)
    @declare_alive_pid = nil
  end
  File.rename(alive_file, terminated_file) if File.exist? alive_file
end

def terminate_file
  File.join(daemon_home, 'terminate-daemon')
end

def terminated_file
  self.class.terminated_file(daemon_home)
end

def termination_file?(pid)
  return false unless File.exist? terminate_file
  say 'Found termination file, terminating'
  File.unlink(terminate_file)
  terminate
  Process.kill(9, pid) unless pid.nil?
  true
end

def write_alive_file
  File.open(alive_file, 'w') { |fh| fh.print Time.now.to_s }
end