class Middleman::Extensions::ExternalPipeline

def initialize(app, config={}, &block)
  super
  return if app.mode?(:config)
  require 'servolux'
  require 'thread'
  require 'fileutils'
  source_path = File.expand_path(options[:source], app.root)
  # Make sure it exists, or `listen` will explode.
  ::FileUtils.mkdir_p(source_path)
  @watcher = app.files.watch :source,
                             path: source_path,
                             latency: options[:latency],
                             frontmatter: false
  @current_thread = nil
  app.reload(&method(:reload!))
  logger.info "== Executing: `#{options[:command]}`"
  if app.build? || options[:disable_background_execution]
    watch_command!(false)
    @watcher.poll_once!
  else
    watch_command!(true)
  end
end

def print_command(stdout)
  while buf = stdout.gets
    without_newline = buf.sub(/\n$/, '')
    logger.info "== External: #{without_newline}" unless without_newline.empty?
  end
end

def reload!
  if @current_thread
    logger.info "== Stopping: `#{options[:command]}`"
    @current_thread.stop
    @current_thread = nil
  end
end

def watch_command!(async)
  @current_thread = ::Servolux::Child.new(
    command: options[:command],
    suspend: 2
  )
  @current_thread.start
  watch_thread = Thread.new do
    while buf = @current_thread.io.gets
      without_newline = buf.sub(/\n$/, '')
      logger.info "== External: #{without_newline}" unless without_newline.empty?
    end
    @current_thread.wait
    if !options[:ignore_exit_code] && !@current_thread.exitstatus.nil? && @current_thread.exitstatus != 0
      logger.error '== External: Command failed with non-zero exit status'
      exit(1)
    end
  end
  watch_thread.join unless async
rescue ::Errno::ENOENT => e
  logger.error "== External: Command failed with message: #{e.message}"
  exit(1)
end