module RSpec::ExampleGroups

def self.assign_const(group)
  base_name   = base_name_for(group)
  const_scope = constant_scope_for(group)
  name        = disambiguate(base_name, const_scope)
  const_scope.const_set(name, group)
end

def self.base_name_for(group)
  return "Anonymous" if group.description.empty?
  # Convert to CamelCase.
  name = ' ' << group.description
  name.gsub!(/[^0-9a-zA-Z]+([0-9a-zA-Z])/) do
    match = ::Regexp.last_match[1]
    match.upcase!
    match
  end
  name.lstrip!                # Remove leading whitespace
  name.gsub!(/\W/, ''.freeze) # JRuby, RBX and others don't like non-ascii in const names
  # Ruby requires first const letter to be A-Z. Use `Nested`
  # as necessary to enforce that.
  name.gsub!(/\A([^A-Z]|\z)/, 'Nested\1'.freeze)
  name
end

def self.constant_scope_for(group)
  const_scope = group.superclass
  const_scope = self if const_scope == ::RSpec::Core::ExampleGroup
  const_scope
end

def self.disambiguate(name, const_scope)
  return name unless const_defined_on?(const_scope, name)
  # Add a trailing number if needed to disambiguate from an existing
  # constant.
  name << "_2"
  name.next! while const_defined_on?(const_scope, name)
  name
end

def base_name_for(group)
  _base_name_for(group) + '_'
end