module Enumeration; end
class Enumeration::Collection

  attr_reader :data

  def initialize(map_or_list)
    unless map_or_list.kind_of?(::Hash) || map_or_list.kind_of?(::Array)
      raise ArgumentError, "please specify the enum collection as a Hash or Array"
    end
    @data = map_or_list
  end

  # lookup collection value by a key
  def [](key)
    if self.map? && @data.has_key?(key)
      @data[key]
    elsif (self.map?  && @data.has_value?(key)) ||
          (self.list? && @data.include?(key))
      key
    else
      nil
    end
  end

  # lookup collection key by a value
  def key(value)
    if self.map? && @data.has_value?(value)
      @data.invert[value]
    elsif (self.map?  && @data.has_key?(value)) ||
          (self.list? && @data.include?(value))
      value
    else
      nil
    end
  end

  def list?
    @data.kind_of?(::Array)
  end

  def map?
    @data.kind_of?(::Hash)
  end

  def set
    self.map? ? @data.keys : @data
  end

end