google_translate.rb

# encoding: UTF-8

#!/usr/bin/ruby

require 'net/http'
require 'net/https'
require 'uri'
require 'json'

class GoogleTranslate
  class TranslationError < StandardError; end

  BASE_URL = 'https://www.googleapis.com/language/translate/v2'

  LANGUAGES = {
    "af"=>"Afrikaans",
    "sq"=>"Albanian",
    "ar"=>"Arabic",
    "az"=>"Azerbaijani",
    "eu"=>"Basque",
    "bn"=>"Bengali",
    "be"=>"Belarusian",
    "bg"=>"Bulgarian",
    "ca"=>"Catalan",
    "zh"=>"Chinese Simplified",
    "zh-TW"=>"Chinese Traditional",
    "hr"=>"Croatian",
    "cs"=>"Czech",
    "da"=>"Danish",
    "nl"=>"Dutch",
    "en"=>"English",
    "eo"=>"Esperanto",
    "et"=>"Estonian",
    "tl"=>"Filipino",
    "fi"=>"Finnish",
    "fr"=>"French",
    "gl"=>"Galician",
    "ka"=>"Georgian",
    "de"=>"German",
    "el"=>"Greek",
    "gu"=>"Gujarati",
    "ht"=>"Haitian Creole",
    "iw"=>"Hebrew",
    "hi"=>"Hindi",
    "hu"=>"Hungarian",
    "is"=>"Icelandic",
    "id"=>"Indonesian",
    "ga"=>"Irish",
    "it"=>"Italian",
    "ja"=>"Japanese",
    "kn"=>"Kannada",
    "ko"=>"Korean",
    "la"=>"Latin",
    "lv"=>"Latvian",
    "lt"=>"Lithuanian",
    "mk"=>"Macedonian",
    "ms"=>"Malay",
    "mt"=>"Maltese",
    "no"=>"Norwegian",
    "fa"=>"Persian",
    "pl"=>"Polish",
    "pt"=>"Portuguese",
    "ro"=>"Romanian",
    "ru"=>"Russian",
    "sr"=>"Serbian",
    "sk"=>"Slovak",
    "sl"=>"Slovenian",
    "es"=>"Spanish",
    "sw"=>"Swahili",
    "sv"=>"Swedish",
    "ta"=>"Tamil",
    "te"=>"Telugu",
    "th"=>"Thai",
    "tr"=>"Turkish",
    "uk"=>"Ukrainian",
    "ur"=>"Urdu",
    "vi"=>"Vietnamese",
    "cy"=>"Welsh",
    "yi"=>"Yiddish"
  }

  attr_accessor :key
  attr_accessor :source
  attr_accessor :target

  def self.api_key
    (config_yaml[Rails.env] || config_yaml['default'])[:server_api_key]
  end

  def self.config_yaml
    YAML.load(File.read 'config/google_api_keys.yml')
  end

  def initialize(options = {})
    @key    = GoogleTranslate.api_key
    @source = options[:source]
    @target = options[:target]
  end

  def translate(string, options = {})
    params = {
      :q => string,
      :source => options[:source] || @source,
      :target => options[:target] || @target
    }

    response = fetch(BASE_URL, params)
    
    translation_from_response(response)
  end

  def detect_language(string)
    url = "#{BASE_URL}/detect"

    params = { :q => string }
    response = fetch(url, params)
   
    raise TranslationError, 'Detection data not present' unless response['data'].andand['detections']
    response['data']['detections'].first.first['language']
  end


  private

  def fetch(url, params)
    uri = URI.parse(url)
    http = Net::HTTP.new(uri.host, 443)
    http.use_ssl = true

    params[:key] = @key
    params.delete_if { |k, v| v.nil? }

    request = Net::HTTP::Post.new(uri.request_uri)
    request.set_form_data(params)
    request['X-HTTP-Method-Override'] = 'GET'
    response = http.request(request).body
    body = JSON.parse(response)

    raise TranslationError, "Invalid response" unless body.kind_of?(Hash)

    if body['error']
      message = "Translate API returned an error: %d (%s)" %
        [ body['error']['code'], body['error']['message'] ]
      raise TranslationError, message
    end

    raise TranslationError, "Translation data not present!" unless body["data"]
    body
  end

  def translation_from_response(response)
    raise TranslationError, "Translation data not present!" unless response["data"].andand['translations']

    response["data"]["translations"].map do |translation_data|
      {
        :translation     => translation_data["translatedText"],
        :detected_source => translation_data["detectedSourceLanguage"]
      }
    end
  end

  def self.supports?(locale)
    LANGUAGES.has_key?(locale)
  end
end