class Guard::Internals::Groups

def add(name, options = {})
  all(name).first || Group.new(name, options).tap do |group|
    fail if name == :specs && options.empty?
    @groups << group
  end
end

def all(filter = nil)
  return @groups if filter.nil?
  matcher = matcher_for(filter)
  @groups.select { |group| matcher.call(group) }
end

def initialize
  @groups = DEFAULT_GROUPS.map { |name| Group.new(name) }
end

def matcher_for(filter)
  case filter
  when String, Symbol
    ->(group) { group.name == filter.to_sym }
  when Regexp
    ->(group) { group.name.to_s =~ filter }
  else
    fail "Invalid filter: #{filter.inspect}"
  end
end