module FakeFS::FileSystem

def add(path, object=FakeDir.new)
  parts = path_parts(normalize_path(path))
  d = parts[0...-1].inject(fs) do |dir, part|
    dir[part] ||= FakeDir.new(part, dir)
  end
  object.name = parts.last
  object.parent = d
  d[parts.last] ||= object
end

def chdir(dir, &blk)
  new_dir = find(dir)
  dir_levels.push dir if blk
  raise Errno::ENOENT, dir unless new_dir
  dir_levels.push dir if !blk
  blk.call if blk
ensure
  dir_levels.pop if blk
end

def clear
  @dir_levels = nil
  @fs = nil
end

def clone(path)
  path    = File.expand_path(path)
  pattern = File.join(path, '**', '*')
  files   = RealFile.file?(path) ? [path] : [path] + RealDir.glob(pattern, RealFile::FNM_DOTMATCH)
  files.each do |f|
    if RealFile.file?(f)
      FileUtils.mkdir_p(File.dirname(f))
      File.open(f, 'w') do |g|
        g.print RealFile.open(f){|h| h.read }
      end
    elsif RealFile.directory?(f)
      FileUtils.mkdir_p(f)
    elsif RealFile.symlink?(f)
      FileUtils.ln_s()
    end
  end
end

def current_dir
  find(normalize_path('.'))
end

def delete(path)
  if dir = FileSystem.find(path)
    dir.parent.delete(dir.name)
  end
end

def dir_levels
  @dir_levels ||= []
end

def files
  fs.values
end

def find(path)
  parts = path_parts(normalize_path(path))
  return fs if parts.empty? # '/'
  entries = find_recurser(fs, parts).flatten
  case entries.length
  when 0 then nil
  when 1 then entries.first
  else entries
  end
end

def find_recurser(dir, parts)
  return [] unless dir.respond_to? :[]
  pattern , *parts = parts
  matches = dir.reject {|k,v| /\A#{pattern.gsub('?','.').gsub('*', '.*')}\Z/ !~ k }.values
  if parts.empty? # we're done recursing
    matches
  else
    matches.map{|entry| find_recurser(entry, parts) }
  end
end

def fs
  @fs ||= FakeDir.new('.')
end

def normalize_path(path)
  if Pathname.new(path).absolute?
    File.expand_path(path)
  else
    parts = dir_levels + [path]
    File.expand_path(File.join(*parts))
  end
end

def path_parts(path)
  path.split(File::PATH_SEPARATOR).reject { |part| part.empty? }
end