require 'geoip'
require 'open-uri'

module Rack
  class GeoLocale
    DATABASE = "tmp/geoip_database.dat"

    def initialize(app)
      fetch_database

      @app = app
    end

    def call(env)
      language, country = parse_locale(env)

      if c = parse_country(env)
        country = c
      end

      language.downcase! if language
      country.upcase! if country

      env["locale.language"] = language
      env["locale.country"] = country

      @app.call(env)
    end

    private
      def parse_country(env)
        if database?
          if remote_addr = env["REMOTE_ADDR"]
            remote_addr = env["HTTP_X_FORWARDED_FOR"] if env["HTTP_X_FORWARDED_FOR"]

            result = geoip.country(remote_addr).country_code2

            return result if result != "--"
          else
            puts "WARNING: Didn't find env['REMOTE_ADDR']"
          end
        else
          puts "WARNING: Didn't find geoip database."
        end

        nil
      end

      def parse_locale(env)
        env["HTTP_ACCEPT_LANGUAGE"] ||= ""
        language_ranges = env["HTTP_ACCEPT_LANGUAGE"].split(",")
        language_ranges.map do |language_range|
          language_range += ';q=1.0' unless language_range =~ /;q=\d+\.\d+$/

          locale, q = language_range.split(";q=")

          language, country = locale.strip.split("-")

          {:language => language, :country => country, :q => q}
        end.sort {|x, y| y[:q] <=> x[:q]}.map{|o| [o[:language], o[:country]]}.first
      end

      def database?
        ::File.exist? DATABASE
      end

      def fetch_database
        if ENV["GEOIP_DATABASE_URI"]
          puts "-> Fetching #{ENV["GEOIP_DATABASE_URI"]}"

          open(ENV["GEOIP_DATABASE_URI"]) do |src|
            data = Zlib::GzipReader.new(StringIO.new(src.read)).read

            open(DATABASE, "wb") {|dst| dst.write(data)}
          end
        else
          puts "WARNING: Set the ENV['GEOIP_DATABASE_URI'] to the location of your .gz database file."
        end
      end

      def geoip
        if database?
          GeoIP.new(DATABASE)
        else
          nil
        end
      end
  end
end