class ActiveSupport::EventedFileUpdateChecker

def changed(modified, added, removed)
  unless updated?
    @updated.make_true if (modified + added + removed).any? { |f| watching?(f) }
  end
end

def directories_to_watch
  dtw = (@files + @dirs.keys).map { |f| @ph.existing_parent(f) }
  dtw.compact!
  dtw.uniq!
  @ph.filter_out_descendants(dtw)
end

def execute
  @updated.make_false
  @block.call
end

def execute_if_updated
  if updated?
    yield if block_given?
    execute
    true
  end
end

def initialize(files, dirs = {}, &block)
  @ph    = PathHelper.new
  @files = files.map { |f| @ph.xpath(f) }.to_set
  @dirs = {}
  dirs.each do |dir, exts|
    @dirs[@ph.xpath(dir)] = Array(exts).map { |ext| @ph.normalize_extension(ext) }
  end
  @block   = block
  @updated = Concurrent::AtomicBoolean.new(false)
  @lcsp    = @ph.longest_common_subpath(@dirs.keys)
  if (dtw = directories_to_watch).any?
    # Loading listen triggers warnings. These are originated by a legit
    # usage of attr_* macros for private attributes, but adds a lot of noise
    # to our test suite. Thus, we lazy load it and disable warnings locally.
    silence_warnings do
      begin
        require 'listen'
      rescue LoadError => e
        raise LoadError, "Could not load the 'listen' gem. Add `gem 'listen'` to the development group of your Gemfile", e.backtrace
      end
    end
    Listen.to(*dtw, &method(:changed)).start
  end
end

def updated?
  @updated.true?
end

def watching?(file)
  file = @ph.xpath(file)
  if @files.member?(file)
    true
  elsif file.directory?
    false
  else
    ext = @ph.normalize_extension(file.extname)
    file.dirname.ascend do |dir|
      if @dirs.fetch(dir, []).include?(ext)
        break true
      elsif dir == @lcsp || dir.root?
        break false
      end
    end
  end
end