/*  South African CPI JavaScript library, version 0.1
 *  (c) 2009 Bryan Allott, http://bryanallott.net/
 *  South African CPI is freely distributable under the terms of an MIT-style license.
 *--------------------------------------------------------------------------*/


var CpiLookup = function() {

  return {
    get_date: function(dateString) {
      var start = 0;
      var token = dateString.indexOf("-", start);
      var year = dateString.substr(start, token - start);
      
      start = token + 1;
      token = dateString.indexOf("-", start);
      var month = dateString.substr(start, token - start);
      
      return new Date(year, month, 20, 0, 0, 0, 0);
      
    },
    
    get_index: function(target_date, table) {
      for(var ii=0;ii<table.data.length;++ii) {
        var index_date = this.get_date(table.data[ii].date);
        if(index_date <= target_date) {
          return table.data[ii].value;
        }
      }
      return 1;
    },
    
    get_real: function(table, nominal_value, nominal_date, real_value, real_date) {
      var real_index = this.get_index(real_date, table);
      var nominal_index = this.get_index(nominal_date, table);
      return nominal_value * (real_index/nominal_index);
    }
  };
}