require "puma/plugin"

# Copied from https://github.com/rails/solid_queue/blob/15408647f1780033dad223d3198761ea2e1e983e/lib/puma/plugin/solid_queue.rb
Puma::Plugin.create do
  attr_reader :puma_pid, :litestream_pid, :log_writer

  def start(launcher)
    @log_writer = launcher.log_writer
    @puma_pid = $$

    launcher.events.on_booted do
      @litestream_pid = fork do
        Thread.new { monitor_puma }
        Litestream::Commands.replicate(async: true)
      end

      in_background do
        monitor_litestream
      end
    end

    launcher.events.on_stopped { stop_litestream }
    launcher.events.on_restart { stop_litestream }
  end

  private

  def stop_litestream
    Process.waitpid(litestream_pid, Process::WNOHANG)
    log_writer.log "Stopping Litestream..."
    Process.kill(:INT, litestream_pid) if litestream_pid
    Process.wait(litestream_pid)
  rescue Errno::ECHILD, Errno::ESRCH
  end

  def monitor_puma
    monitor(:puma_dead?, "Detected Puma has gone away, stopping Litestream...")
  end

  def monitor_litestream
    monitor(:litestream_dead?, "Detected Litestream has gone away, stopping Puma...")
  end

  def monitor(process_dead, message)
    loop do
      if send(process_dead)
        log message
        Process.kill(:INT, $$)
        break
      end
      sleep 2
    end
  end

  def litestream_dead?
    Process.waitpid(litestream_pid, Process::WNOHANG)
    false
  rescue Errno::ECHILD, Errno::ESRCH
    true
  end

  def puma_dead?
    Process.ppid != puma_pid
  end

  def log(...)
    log_writer.log(...)
  end
end