transliterate.rb

require 'active_support/core_ext/string/multibyte'
require 'active_support/i18n'

module ActiveSupport
  module Inflector

    # Replaces non-ASCII characters with an ASCII approximation, or if none
    # exists, a replacement character which defaults to "?".
    #
    #    transliterate('Ærøskøbing')
    #    # => "AEroskobing"
    #
    # Default approximations are provided for Western/Latin characters,
    # e.g, "ø", "ñ", "é", "ß", etc.
    #
    # This method is I18n aware, so you can set up custom approximations for a
    # locale. This can be useful, for example, to transliterate German's "ü"
    # and "ö" to "ue" and "oe", or to add support for transliterating Russian
    # to ASCII.
    #
    # In order to make your custom transliterations available, you must set
    # them as the <tt>i18n.transliterate.rule</tt> i18n key:
    #
    #   # Store the transliterations in locales/de.yml
    #   i18n:
    #     transliterate:
    #       rule:
    #         ü: "ue"
    #         ö: "oe"
    #
    #   # Or set them using Ruby
    #   I18n.backend.store_translations(:de, i18n: {
    #     transliterate: {
    #       rule: {
    #         'ü' => 'ue',
    #         'ö' => 'oe'
    #       }
    #     }
    #   })
    #
    # The value for <tt>i18n.transliterate.rule</tt> can be a simple Hash that
    # maps characters to ASCII approximations as shown above, or, for more
    # complex requirements, a Proc:
    #
    #   I18n.backend.store_translations(:de, i18n: {
    #     transliterate: {
    #       rule: ->(string) { MyTransliterator.transliterate(string) }
    #     }
    #   })
    #
    # Now you can have different transliterations for each locale:
    #
    #   I18n.locale = :en
    #   transliterate('Jürgen')
    #   # => "Jurgen"
    #
    #   I18n.locale = :de
    #   transliterate('Jürgen')
    #   # => "Juergen"
    def transliterate(string, replacement = "?".freeze)
      I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize(
        ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c),
          :replacement => replacement)
    end

    # Replaces special characters in a string so that it may be used as part of
    # a 'pretty' URL.
    #
    #   parameterize("Donald E. Knuth") # => "donald-e-knuth"
    #   parameterize("^trés|Jolie-- ")  # => "tres-jolie"
    #
    # To use a custom separator, override the `separator` argument.
    #
    #  parameterize("Donald E. Knuth", separator: '_') # => "donald_e_knuth"
    #  parameterize("^trés|Jolie-- ", separator: '_')  # => "tres_jolie"
    #
    # To preserve the case of the characters in a string, use the `preserve_case` argument.
    #
    #   parameterize("Donald E. Knuth", preserve_case: true) # => "Donald-E-Knuth"
    #   parameterize("^trés|Jolie-- ", preserve_case: true) # => "tres-Jolie"
    #
    def parameterize(string, sep = :unused, separator: '-', preserve_case: false)
      unless sep == :unused
        ActiveSupport::Deprecation.warn("Passing the separator argument as a positional parameter is deprecated and will soon be removed. Use `separator: '#{sep}'` instead.")
        separator = sep
      end
      # Replace accented chars with their ASCII equivalents.
      parameterized_string = transliterate(string)

      # Turn unwanted chars into the separator.
      parameterized_string.gsub!(/[^a-z0-9\-_]+/i, separator)

      unless separator.nil? || separator.empty?
        if separator == "-".freeze
          re_duplicate_separator        = /-{2,}/
          re_leading_trailing_separator = /^-|-$/i
        else
          re_sep = Regexp.escape(separator)
          re_duplicate_separator        = /#{re_sep}{2,}/
          re_leading_trailing_separator = /^#{re_sep}|#{re_sep}$/i
        end
        # No more than one of the separator in a row.
        parameterized_string.gsub!(re_duplicate_separator, separator)
        # Remove leading/trailing separator.
        parameterized_string.gsub!(re_leading_trailing_separator, ''.freeze)
      end
      
      parameterized_string.downcase! unless preserve_case
      parameterized_string
    end
  end
end