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

  # Returns the plural form of the word in the string.
  #
  # Examples
  #   "post".pluralize #=> "posts"
  #   "octopus".pluralize #=> "octopi"
  #   "sheep".pluralize #=> "sheep"
  #   "words".pluralize #=> "words"
  #   "the blue mailman".pluralize #=> "the blue mailmen"
  #   "CamelOctopus".pluralize #=> "CamelOctopi"
  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

  # The reverse of pluralize, returns the singular form of a word in a string.
  #
  # Examples
  #   "posts".singularize #=> "post"
  #   "octopi".singularize #=> "octopus"
  #   "sheep".singluarize #=> "sheep"
  #   "word".singluarize #=> "word"
  #   "the blue mailmen".singularize #=> "the blue mailman"
  #   "CamelOctopi".singularize #=> "CamelOctopus"
  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

  # By default, camelize converts strings to UpperCamelCase. If the argument to camelize
  # is set to ":lower" then camelize produces lowerCamelCase.
  #
  # camelize will also convert '/' to '::' which is useful for converting paths to namespaces
  #
  # Examples
  #   "active_record".camelize #=> "ActiveRecord"
  #   "active_record".camelize(:lower) #=> "activeRecord"
  #   "active_record/errors".camelize #=> "ActiveRecord::Errors"
  #   "active_record/errors".camelize(:lower) #=> "activeRecord::Errors"
  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

  # Capitalizes all the words and replaces some characters in the string to create
  # a nicer looking title. Titleize is meant for creating pretty output. It is not
  # used in the Rails internals.
  #
  # titleize is also aliased as as titlecase
  #
  # Examples
  #   "man from the boondocks".titleize #=> "Man From The Boondocks"
  #   "x-men: the last stand".titleize #=> "X Men: The Last Stand"
  def titleize(word)
    humanize(underscore(word)).gsub(/\b([a-z])/) { $1.capitalize }
  end

  # The reverse of +camelize+. Makes an underscored form from the expression in the string.
  #
  # Changes '::' to '/' to convert namespaces to paths.
  #
  # Examples
  #   "ActiveRecord".underscore #=> "active_record"
  #   "ActiveRecord::Errors".underscore #=> active_record/errors
  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

  # Replaces underscores with dashes in the string.
  #
  # Example
  #   "puni_puni" #=> "puni-puni"
  def dasherize(underscored_word)
    underscored_word.gsub(/_/, '-')
  end

  # Capitalizes the first word and turns underscores into spaces and strips _id.
  # Like titleize, this is meant for creating pretty output.
  #
  # Examples
  #   "employee_salary" #=> "Employee salary"
  #   "author_id" #=> "Author"
  def humanize(lower_case_and_underscored_word)
    lower_case_and_underscored_word.to_s.gsub(/_id$/, "").gsub(/_/, " ").capitalize
  end

  # Removes the module part from the expression in the string
  #
  # Examples
  #   "ActiveRecord::CoreExtensions::String::Inflections".demodulize #=> "Inflections"
  #   "Inflections".demodulize #=> "Inflections"
  def demodulize(class_name_in_module)
    class_name_in_module.to_s.gsub(/^.*::/, '')
  end

  # Create the name of a table like Rails does for models to table names. This method
  # uses the pluralize method on the last word in the string.
  #
  # Examples
  #   "RawScaledScorer".tableize #=> "raw_scaled_scorers"
  #   "egg_and_ham".tableize #=> "egg_and_hams"
  #   "fancyCategory".tableize #=> "fancy_categories"
  def tableize(class_name)
    pluralize(underscore(class_name))
  end

  # Create a class name from a table name like Rails does for table names to models.
  # Note that this returns a string and not a Class. (To convert to an actual class
  # follow classify with constantize.)
  #
  # Examples
  #   "egg_and_hams".classify #=> "EggAndHam"
  #   "post".classify #=> "Post"
  def classify(table_name)
    # strip out any leading schema name
    camelize(singularize(table_name.to_s.sub(/.*\./, '')))
  end

  # Creates a foreign key name from a class name.
  # +separate_class_name_and_id_with_underscore+ sets whether
  # the method should put '_' between the name and 'id'.
  #
  # Examples
  #   "Message".foreign_key #=> "message_id"
  #   "Message".foreign_key(false) #=> "messageid"
  #   "Admin::Post".foreign_key #=> "post_id"
  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

  # Constantize tries to find a declared constant with the name specified
  # in the string. It raises a NameError when the name is not in CamelCase
  # or is not initialized.
  #
  # Examples
  #   "Module".constantize #=> Module
  #   "Class".constantize #=> Class
  def constantize(camel_cased_word)
    unless /\A(?:::)?([A-Z]\w*(?:::[A-Z]\w*)*)\z/ =~ camel_cased_word
      raise NameError, "#{camel_cased_word.inspect} is not a valid constant name!"
    end

    Object.module_eval("::#{$1}", __FILE__, __LINE__)
  end

  # Ordinalize turns a number into an ordinal string used to denote the
  # position in an ordered sequence such as 1st, 2nd, 3rd, 4th.
  #
  # Examples
  #   ordinalize(1)     # => "1st"
  #   ordinalize(2)     # => "2nd"
  #   ordinalize(1002)  # => "1002nd"
  #   ordinalize(1003)  # => "1003rd"
  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'