get_nab_account_balances.rb

require 'rubygems'
require 'nokogiri'
require 'mechanize'
require 'logger'

module BankBalance

  class NabFetcher

    def fetch(client_number, password)
      agent = WWW::Mechanize.new() do |a|
        a.log = Logger.new("mech.log")
        a.user_agent_alias = 'Mac FireFox'
        # http://rubyforge.org/tracker/index.php?func=detail&aid=24950&group_id=1453&atid=5709
        a.keep_alive = false # For slow site
      end
      # puts "Requesting login page"
      login_page = agent.get('https://ib.nab.com.au/nabib/index.jsp')
      login_form = login_page.form('sf_1')

      key = ''
      alphabet = ''
      sf1_password = 'document\.sf_1\.password\.value'
      login_page.search('//script[6]').each do |js|
        if js.text =~  /#{sf1_password}=check\(#{sf1_password},"([^"]+)","([^"]+)"\);/
          key = $1
          alphabet = $2
        end
      end

      login_form.userid = client_number
      login_form.password = check(password, key, alphabet)

      accounts = []
      # puts "Submitting login form"
      balances_page = agent.submit(login_form)
      balances_page.root.css('table#accountBalances_nonprimary_subaccounts tbody tr').each do |elem|
        accounts << {
          :name => elem.css('td:first-child').text.strip,
          :balance => elem.css('td:last-child').text.strip.gsub(',', '').to_f,
          :formatted_balance => elem.css('td:last-child').text.strip.sub(/^(-?)(.*)$/, '\1$\2'),
        }
        
        # puts "#{account_name}: #{account_balance}"
      end

      # Logout, not sure if this is the right path though
      # puts "Logging out"
      agent.get('https://ib.nab.com.au/nabib/preLogout.ctl')
      
      accounts
    end

    protected

    def check(p, k, a)
      # Implementation of the following javascript function
      # function check(p, k, a) {
      #   for (var i=a.length-1;i>0;i--) {
      #     if (i!=a.indexOf(a.charAt(i))) {
      #       a=a.substring(0,i)+a.substring(i+1);
      #     }
      #   }
      #   var r=new Array(p.length);
      #   for (var i=0;i<p.length;i++) {
      #     r[i]=p.charAt(i);
      #     var pi=a.indexOf(p.charAt(i));
      #     if (pi>=0 && i<k.length) {
      #       var ki=a.indexOf(k.charAt(i));
      #       if (ki>=0) {
      #         pi-=ki;
      #         if (pi<0) pi+=a.length;
      #         r[i]=a.charAt(pi);
      #       }
      #     }
      #   }
      #   return r.join("");
      # }

      # puts "check(password, #{k})"

      # 0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
      # Generate this above as an array of chars
      r = []
      last_index = p.length - 1
      # TODO: Use the passed alphabet instead
      alphabet = ('0'..'9').to_a + ('a'..'z').to_a + ('A'..'Z').to_a
      (0..last_index).each do |i|
        r[i] = p[i,1]

        pi = alphabet.index(r[i])
        unless pi.nil? or i >= k.length
          ki = alphabet.index(k[i,1])
          unless ki.nil?
            pi -= ki
            pi += alphabet.size if pi < 0
            r[i] = alphabet[pi]
          end
        end
      end
      r.join('')
    end

  end

end