var raster = new ol.layer.Tile({
  source: new ol.source.OSM()
});

var vector = new ol.layer.Vector({
  source: new ol.source.Vector({
    url: 'data/geojson/countries.geojson',
    format: new ol.format.GeoJSON()
  })
});

var map = new ol.Map({
  layers: [raster, vector],
  target: 'map',
  view: new ol.View({
    center: [0, 0],
    zoom: 2
  })
});

var select = null;  // ref to currently selected interaction

// select interaction working on "singleclick"
var selectSingleClick = new ol.interaction.Select();

// select interaction working on "click"
var selectClick = new ol.interaction.Select({
  condition: ol.events.condition.click
});

// select interaction working on "pointermove"
var selectPointerMove = new ol.interaction.Select({
  condition: ol.events.condition.pointerMove
});

var selectAltClick = new ol.interaction.Select({
  condition: function(mapBrowserEvent) {
    return ol.events.condition.click(mapBrowserEvent) &&
        ol.events.condition.altKeyOnly(mapBrowserEvent);
  }
});

var selectElement = document.getElementById('type');

var changeInteraction = function() {
  if (select !== null) {
    map.removeInteraction(select);
  }
  var value = selectElement.value;
  if (value == 'singleclick') {
    select = selectSingleClick;
  } else if (value == 'click') {
    select = selectClick;
  } else if (value == 'pointermove') {
    select = selectPointerMove;
  } else if (value == 'altclick') {
    select = selectAltClick;
  } else {
    select = null;
  }
  if (select !== null) {
    map.addInteraction(select);
    select.on('select', function(e) {
      document.getElementById('status').innerHTML = '&nbsp;' +
          e.target.getFeatures().getLength() +
          ' selected features (last operation selected ' + e.selected.length +
          ' and deselected ' + e.deselected.length + ' features)';
    });
  }
};


/**
 * onchange callback on the select element.
 */
selectElement.onchange = changeInteraction;
changeInteraction();
