rails--rails/activesupport/lib/active_support/inflector.rb

require 'singleton' 

# The Inflector transforms words from singular to plural, class names to table names, modularized class names to ones without,
# and class names to foreign keys. The default inflections for pluralization, singularization, and uncountable words are kept
# in inflections.rb.
module Inflector 
  # A singleton instance of this class is yielded by Inflector.inflections, which can then be used to specify additional
  # inflection rules. Examples:
  #
  #   Inflector.inflections do |inflect|
  #     inflect.plural /^(ox)$/i, '\1\2en'
  #     inflect.singular /^(ox)en/i, '\1'
  #
  #     inflect.irregular 'octopus', 'octopi'
  #
  #     inflect.uncountable "equipment"
  #   end
  #
  # New rules are added at the top. So in the example above, the irregular rule for octopus will now be the first of the
  # pluralization and singularization rules that is runs. This guarantees that your rules run before any of the rules that may
  # already have been loaded.
  class Inflections
    include Singleton
    
    attr_reader :plurals, :singulars, :uncountables
    
    def initialize
      @plurals, @singulars, @uncountables = [], [], []
    end
    
    # Specifies a new pluralization rule and its replacement. The rule can either be a string or a regular expression. 
    # The replacement should always be a string that may include references to the matched data from the rule.
    def plural(rule, replacement)
      @plurals.insert(0, [rule, replacement])
    end
    
    # Specifies a new singularization rule and its replacement. The rule can either be a string or a regular expression. 
    # The replacement should always be a string that may include references to the matched data from the rule.
    def singular(rule, replacement)
      @singulars.insert(0, [rule, replacement])
    end

    # Specifies a new irregular that applies to both pluralization and singularization at the same time. This can only be used
    # for strings, not regular expressions. You simply pass the irregular in singular and plural form.
    # 
    # Examples:
    #   irregular 'octopus', 'octopi'
    #   irregular 'person', 'people'
    def irregular(singular, plural)
      plural(Regexp.new("(#{singular[0,1]})#{singular[1..-1]}$", "i"), '\1' + plural[1..-1])
      singular(Regexp.new("(#{plural[0,1]})#{plural[1..-1]}$", "i"), '\1' + singular[1..-1])
    end
    
    # Add uncountable words that shouldn't be attempted inflected.
    # 
    # Examples:
    #   uncountable "money"
    #   uncountable "money", "information"
    #   uncountable %w( money information rice )
    def uncountable(*words)
      (@uncountables << words).flatten!
    end
    
    # Clears the loaded inflections within a given scope (default is :all). Give the scope as a symbol of the inflection type,
    # the options are: :plurals, :singulars, :uncountables
    #
    # Examples:
    #   clear :all
    #   clear :plurals
    def clear(scope = :all)
      case scope
        when :all
          @plurals, @singulars, @uncountables = [], [], []
        else
          instance_variable_set "@#{scope}", []
      end
    end
  end

  extend self

  def inflections
    if block_given?
      yield Inflections.instance
    else
      Inflections.instance
    end
  end

  def pluralize(word)
    result = word.to_s.dup

    if inflections.uncountables.include?(result.downcase)
      result
    else
      inflections.plurals.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
      result
    end
  end

  def singularize(word)
    result = word.to_s.dup

    if inflections.uncountables.include?(result.downcase)
      result
    else
      inflections.singulars.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
      result
    end
  end

  def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)
    if first_letter_in_uppercase
      lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::" + $1.upcase }.gsub(/(^|_)(.)/) { $2.upcase }
    else
      lower_case_and_underscored_word.first + camelize(lower_case_and_underscored_word)[1..-1]
    end
  end

  def titleize(word)
    humanize(underscore(word)).gsub(/\b([a-z])/) { $1.capitalize }
  end
  
  def underscore(camel_cased_word)
    camel_cased_word.to_s.gsub(/::/, '/').
      gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
      gsub(/([a-z\d])([A-Z])/,'\1_\2').
      tr("-", "_").
      downcase
  end
  
  def dasherize(underscored_word)
    underscored_word.gsub(/_/, '-')
  end

  def humanize(lower_case_and_underscored_word)
    lower_case_and_underscored_word.to_s.gsub(/_id$/, "").gsub(/_/, " ").capitalize
  end

  def demodulize(class_name_in_module)
    class_name_in_module.to_s.gsub(/^.*::/, '')
  end

  def tableize(class_name)
    pluralize(underscore(class_name))
  end
  
  def classify(table_name)
    # strip out any leading schema name
    camelize(singularize(table_name.to_s.sub(/.*\./, '')))
  end

  def foreign_key(class_name, separate_class_name_and_id_with_underscore = true)
    underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id")
  end

  def constantize(camel_cased_word)
    raise NameError, "#{camel_cased_word.inspect} is not a valid constant name!" unless
      /^(::)?([A-Z]\w*)(::[A-Z]\w*)*$/ =~ camel_cased_word
    
    camel_cased_word = "::#{camel_cased_word}" unless $1
    Object.module_eval(camel_cased_word, __FILE__, __LINE__)
  end

  def ordinalize(number)
    if (11..13).include?(number.to_i % 100)
      "#{number}th"
    else
      case number.to_i % 10
        when 1: "#{number}st"
        when 2: "#{number}nd"
        when 3: "#{number}rd"
        else    "#{number}th"
      end
    end
  end
end

require File.dirname(__FILE__) + '/inflections'