class SassListen::Adapter::Darwin

def self.usable?
  require 'rb-fsevent'
  darwin_version = RbConfig::CONFIG['target_os'][OS_REGEXP, :major_version] or return false
  return true if darwin_version.to_i >= 13 # darwin13 is OS X 10.9
  return true if Gem::Version.new(FSEvent::VERSION) <= Gem::Version.new('0.9.4')
  Kernel.warn INCOMPATIBLE_GEM_VERSION
  false
end

def _configure(dir, &callback)
  opts = { latency: options.latency }
  @workers ||= ::Queue.new
  @workers << FSEvent.new.tap do |worker|
    _log :debug, "fsevent: watching: #{dir.to_s.inspect}"
    worker.watch(dir.to_s, opts, &callback)
  end
end

def _process_event(dir, event)
  _log :debug, "fsevent: processing event: #{event.inspect}"
  event.each do |path|
    new_path = Pathname.new(path.sub(/\/$/, ''))
    _log :debug, "fsevent: #{new_path}"
    # TODO: does this preserve symlinks?
    rel_path = new_path.relative_path_from(dir).to_s
    _queue_change(:dir, dir, rel_path, recursive: true)
  end
end

def _run
  first = @workers.pop
  # NOTE: _run is called within a thread, so run every other
  # worker in it's own thread
  _run_workers_in_background(_to_array(@workers))
  _run_worker(first)
end

def _run_worker(worker)
  _log :debug, "fsevent: running worker: #{worker.inspect}"
  worker.run
rescue
  _log_exception 'fsevent: running worker failed: %s:%s called from: %s', caller
end

def _run_workers_in_background(workers)
  workers.each do |worker|
    # NOTE: while passing local variables to the block below is not
    # thread safe, using 'worker' from the enumerator above is ok
    SassListen::Internals::ThreadPool.add { _run_worker(worker) }
  end
end

def _to_array(queue)
  workers = []
  workers << queue.pop until queue.empty?
  workers
end