rackjs_middleware.rb

require "json"
require "rack/contrib/simple_endpoint"

MINIFIED_LIB = <<EOJS
var I18n=I18n||(function(){function a(g,f){return g.replace(/\{\{([^}]+)\}\}/g,function(){return f[arguments[1]]||arguments[0]})}function c(f){if(!f){return[]}if(typeof f!="string"){return f}return f.split(".")}function d(g,j){var f=0,h=I18n.translations;j=(typeof j==="string")?[j]:(j||[]);while(g[f]){h=h&&h[g[f]];f++}if(h){return h}else{if(j.length===0){return null}else{if(j[0].substr(0,1)===":"){return d(g.slice(0,g.length-1).concat(c(j[0].substr(1))),j.slice(1))}else{return j[0]}}}}function b(g,f){if(f===undefined){return g}return f===1?g.one:g.other}function e(j,g){if(typeof j!="string"){var f=[],h;for(h=0;h<j.length;h++){f.push(e(j[h],g))}return f}else{g=g||{};g.defaultValue=g.defaultValue||null;j=c(g.scope).concat(c(j));var k=d(j,g.defaultValue);if(typeof k!=="string"&&k){k=b(k,g.count)}if(typeof k==="string"){k=a(k,g)}return k}}return{translate:e,t:e}})();
EOJS

class RackjsMiddleware < Rack::SimpleEndpoint
  def initialize(app, options = {})
    @options = options
    super(app, path_regexp) do |request, response, match|
      response["Content-Type"] = "application/javascript"
      compiled(match[1])
    end
  end

  private

  def path
    @options.fetch(:path, "/javascripts/i18n").sub(%r{/$}, "")
  end

  def path_regexp
    %r{^#{path}/(#{available_locales.join("|")}).js$}
  end

  def translations
    I18n.backend.send(:init_translations) if I18n.backend.send(:translations).empty?
    I18n.backend.send(:translations)
  end

  def available_locales
    translations.keys
  end

  def compiled(locale)
    "I18n.locale=I18n.locale||\"#{locale}\";I18n.translations=I18n.translations||#{translations[locale].to_json};#{MINIFIED_LIB}"
  end
end