var minFirst;
var changeFirst;
var per_sk_used = 'per_sk_60';
var how;

function check(what, val){

  document.getElementById('per_sk_60').style.display = "none";
  document.getElementById('per_sk_36').style.display = "none";
  document.getElementById('per_sk_24').style.display = "none";
  document.getElementById('per_sk_12').style.display = "none";
  document.getElementById('per_sk_6').style.display = "none";
  document.getElementById('per_sk').style.display = "none";

	if(navigator.userAgent.indexOf('Firefox') > -1 || navigator.userAgent.indexOf('Opera') > -1)
	   how = "block";
	else
	   how = "block";

	switch(val){
			case 'cred':
				  	 document.getElementById(per_sk_used).style.display = how;
						 break;
			case 'mob':
				  	 document.getElementById(per_sk_used).style.display = how;
						 break;
		  }

	do_calculation();

  }

function do_calculation(){

		if(document.getElementById('object').value == 'cred' || document.getElementById('object').value == 'mob'){

		  value = document.getElementById('summa').value;
		  per_sk = document.getElementById(per_sk_used).value;
      index = document.getElementById(per_sk_used).selectedIndex;

      if(document.getElementById('summa').value <= 300){
        if(document.getElementById('num_buy_cred').value == 1){
          rate = 0.02333;
          }
        if(document.getElementById('num_buy_cred').value == 2){
          rate = 0.02250;
          }
        if(document.getElementById('num_buy_cred').value == 3){
          rate = 0.02167;
          }
        if(document.getElementById('num_buy_cred').value == 4){
          rate = 0.02167;
          }
        }

      if(document.getElementById('summa').value > 300 && document.getElementById('summa').value <= 500){
        if(document.getElementById('num_buy_cred').value == 1){
          rate = 0.02167;
          }
        if(document.getElementById('num_buy_cred').value == 2){
          rate = 0.02083;
          }
        if(document.getElementById('num_buy_cred').value == 3){
          rate = 0.0175;
          }
        if(document.getElementById('num_buy_cred').value == 4){
          rate = 0.02;
          }
        }

      if(document.getElementById('summa').value > 500 && document.getElementById('summa').value <= 2500){
        if(document.getElementById('num_buy_cred').value == 1){
          rate = 0.02083;
          }
        if(document.getElementById('num_buy_cred').value == 2){
          rate = 0.02;
          }
        if(document.getElementById('num_buy_cred').value == 3){
          rate = 0.01666;
          }
        if(document.getElementById('num_buy_cred').value == 4){
          rate = 0.01917;
          }
        }

      if(document.getElementById('summa').value > 2500){
        if(document.getElementById('num_buy_cred').value == 1){
          rate = 0.02;
          }
        if(document.getElementById('num_buy_cred').value == 2){
          rate = 0.01917;
          }
        if(document.getElementById('num_buy_cred').value == 3){
          rate = 0.01333;
          }
        if(document.getElementById('num_buy_cred').value == 4){
          rate = 0.01833;
          }
        if(document.getElementById('num_buy_cred').value == 5){
          rate = 0.01166;
          }
        }

      if(document.getElementById('object').value == 'mob'){
        minFirst = document.getElementById('summa').value / 10;
        first = document.getElementById('first_ls').value;
        if(first > document.getElementById('summa').value / 2) document.getElementById('first_ls').value = minFirst;
        if(document.getElementById('num_buy_cred').value == 1){
          if(first < minFirst) document.getElementById('first_ls').value = minFirst.toFixed(2);
          rate = 0.02416;
          }
        if(document.getElementById('num_buy_cred').value == 2){
          if(first < minFirst) document.getElementById('first_ls').value = minFirst.toFixed(2);
          rate = 0.02333;
          }
        if(document.getElementById('num_buy_cred').value == 3){
          rate = 0.01333;
          }
        if(document.getElementById('num_buy_cred').value == 4){
          rate = 0.02167;
          }
        }

        if(per_sk_used == 'per_sk_60'){
          if(document.getElementById('summa').value <= 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_6';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 6) index = 0;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value <= 200 && document.getElementById('summa').value > 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_12';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 12) index = 1;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value <= 300 && document.getElementById('summa').value > 200){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_24';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 24) index = 3;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value <= 1000 && document.getElementById('summa').value > 300){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_36';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 36) index = 4;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          }
        else if(per_sk_used == 'per_sk_36'){
          if(document.getElementById('summa').value <= 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_6';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 6) index = 0;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value <= 200 && document.getElementById('summa').value > 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_12';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 12) index = 1;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value <= 300 && document.getElementById('summa').value > 200){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_24';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 24) index = 3;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_60';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          }
        else if(per_sk_used == 'per_sk_24'){
          if(document.getElementById('summa').value <= 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_6';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 6) index = 0;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value <= 200 && document.getElementById('summa').value > 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_12';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 12) index = 1;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 300 && document.getElementById('summa').value <= 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_36';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_60';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          }
        else if(per_sk_used == 'per_sk_12'){
          if(document.getElementById('summa').value <= 100){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_6';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            if(per_sk > 6) index = 0;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 200 && document.getElementById('summa').value <= 300){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_24';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 300 && document.getElementById('summa').value <= 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_36';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_60';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          }
        else{
          if(document.getElementById('summa').value > 100 && document.getElementById('summa').value <= 200){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_12';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 200 && document.getElementById('summa').value <= 300){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_24';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 300 && document.getElementById('summa').value <= 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_36';
  	   	  	document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            }
          if(document.getElementById('summa').value > 1000){
            document.getElementById(per_sk_used).style.display = "none";
            per_sk_used = 'per_sk_60';
  		  	  document.getElementById(per_sk_used).style.display = how;
            document.getElementById(per_sk_used).selectedIndex = index;
            //document.getElementById(per_sk_used).value = per_sk;
            }
          }

      form = 0;
      service = 0;
      ctrl = 0;
      minFirst = 0;
		  value = document.getElementById('summa').value;
		  first = document.getElementById('first_ls').value;
		  per_sk = document.getElementById(per_sk_used).value;

      //monthly = (value - first + form + value*ctrl);
      monthly = value - (first - minFirst);
      sauc = Math.pow(1 + rate, per_sk) - 1;
      fullRate = rate + (rate/sauc);
      monthly = monthly * fullRate + service;
      monthly = monthly.toFixed(2);
      if(document.getElementById('summa').value < 50) { document.getElementById('res').value = '-'; }
      else { document.getElementById('res').value = monthly + ' LVL'; }
      //document.getElementById('res').value = rate;
      changeFirst = 1;
	    //document.getElementById('debugInfo').innerHTML = index;
		  }


}