Rails locale formatter

locale_formatter.rb

#!/usr/bin/env ruby
# encoding: utf-8

require 'yaml'
require 'stringio'

class LocaleFormatter
  ESCAPE_KEYS = %w(true false yes no on off)
  ESCAPE_VALUE_RE = /[^[:alnum:]_\-\/\.\?]/
  MULTILINE_INDENT_LEVEL = 2

  def initialize(yaml)
    @locale = YAML.load(yaml)
  end

  def to_s
    stream = StringIO.new
    stream.puts "---"
    print_locale(stream, @locale)
    stream.rewind
    stream.read
  end

  private

  def print_locale(stream, tree, level = 0)
    tree.sort_by { |k, v| k }.each do |key, values|
      if values.is_a?(Hash)
        stream.puts indent("#{ escape_key(key) }:", level)
        print_locale(stream, values, level.next)
      elsif values.include?("\n")
        stream.puts indent("#{ escape_key(key) }: |", level)
        stream.puts indent(values, level + MULTILINE_INDENT_LEVEL)
      elsif values.match(ESCAPE_VALUE_RE)
        stream.puts indent("#{ escape_key(key) }: #{ values.inspect }", level)
      else
        stream.puts indent("#{ escape_key(key) }: #{ values }", level)
      end
    end
  end

  def indent(str, level)
    str.gsub(/^/, "  " * level)
  end

  def escape_key(key)
    if ESCAPE_KEYS.include?(key)
      "\"#{ key }\""
    else
      key
    end
  end
end

puts LocaleFormatter.new(ARGF.read)