var selects = document.querySelector('.selects');
var weatherDiv = document.querySelector('.weather');

function get(url){
  return new Promise(function(resolve,reject){
    var xhr = new XMLHttpRequest();
    xhr.open('GET',url,true);
    xhr.onload = function(){
      if(xhr.status == 200){
        resolve(JSON.parse(xhr.responseText));
      }
      else{
        reject(xhr.statusText);
      }
    }
    xhr.onerror = function(){
      reject('not found');
    }
    xhr.send();
  });
}
function show(obj){
  var weather = obj.query.results.channel.item.description;
  var resWeather = weather.replace(/href|CDATA|[\!]|[\[]|[\]]/g,"");
  var resWeather2 = resWeather.slice(1,resWeather.length - 1);
  var resWeather3 = resWeather2.replace(/Full Forecast at Yahoo Weather/g,"");
  var resWeather4 = resWeather3.slice(0,resWeather3.length - 28);
  weatherDiv.innerHTML = resWeather4;
}

function* myGenerator(){
    var object = yield get('https://raw.githubusercontent.com/David-Haim/CountriesToCitiesJSON/master/countriesToCities.json');
    var keys = Object.keys(object);
    var select = document.createElement("select");
    for (var i = 0; i < keys.length; i++) {
        var option = document.createElement("option");
        option.innerHTML = keys[i];
        option.value = keys[i];
        select.appendChild(option);
    }

    select.onchange = function(){
      run(onchange1);
    }
    function* onchange1(e){
        var select = document.createElement("select");
        for (var i = 0; i < object[document.getElementById("main").value].length; i++) {
            var option = document.createElement("option")
            option.innerHTML = object[document.getElementById("main").value][i];
            select.appendChild(option);
        }
        if(selects.children.length > 1){
            selects.replaceChild(select, document.getElementById("main").nextElementSibling);
        }
        else
            selects.appendChild(select);
          var obj = yield get("https://query.yahooapis.com/v1/public/yql?" + 'q=' + encodeURIComponent("select * from weather.forecast where woeid in (select woeid from geo.places(1) where text=\'" + select.value + "\') and u='c'") + '&format=json');
          show(obj);
        select.onchange = function(){
          get("https://query.yahooapis.com/v1/public/yql?" + 'q=' + encodeURIComponent("select * from weather.forecast where woeid in (select woeid from geo.places(1) where text=\'" + this.value + "\') and u='c'") + '&format=json').then(function(obj){
            show(obj);
          })
        }
    }
    selects.appendChild(select);
    select.id = "main"

}

function run(g){
  var gen = g();
  function handle(result){
      if(!result.done){
        result.value.then(function(data){
          return handle(gen.next(data));
        })
      }
  }
  return handle(gen.next());
}
run(myGenerator);