// FIXME works for View2D only

goog.provide('ol.interaction.DragPan');

goog.require('goog.asserts');
goog.require('ol.Kinetic');
goog.require('ol.PreRenderFunction');
goog.require('ol.View2D');
goog.require('ol.ViewHint');
goog.require('ol.coordinate');
goog.require('ol.events.ConditionType');
goog.require('ol.events.condition');
goog.require('ol.interaction.Drag');



/**
 * Allows the user to pan the map by clickng and dragging.
 * @constructor
 * @extends {ol.interaction.Drag}
 * @param {olx.interaction.DragPanOptions=} opt_options Options.
 * @todo stability experimental
 */
ol.interaction.DragPan = function(opt_options) {

  goog.base(this);

  var options = goog.isDef(opt_options) ? opt_options : {};

  /**
   * @private
   * @type {ol.events.ConditionType}
   */
  this.condition_ = goog.isDef(options.condition) ?
      options.condition : ol.events.condition.noModifierKeys;

  /**
   * @private
   * @type {ol.Kinetic|undefined}
   */
  this.kinetic_ = options.kinetic;

  /**
   * @private
   * @type {?ol.PreRenderFunction}
   */
  this.kineticPreRenderFn_ = null;

};
goog.inherits(ol.interaction.DragPan, ol.interaction.Drag);


/**
 * @inheritDoc
 */
ol.interaction.DragPan.prototype.handleDrag = function(mapBrowserEvent) {
  if (this.kinetic_) {
    this.kinetic_.update(
        mapBrowserEvent.browserEvent.clientX,
        mapBrowserEvent.browserEvent.clientY);
  }
  var map = mapBrowserEvent.map;
  // FIXME works for View2D only
  var view = map.getView();
  goog.asserts.assertInstanceof(view, ol.View2D);
  var view2DState = view.getView2DState();
  var newCenter = [
    -view2DState.resolution * this.deltaX,
    view2DState.resolution * this.deltaY
  ];
  ol.coordinate.rotate(newCenter, view2DState.rotation);
  ol.coordinate.add(newCenter, this.startCenter);
  newCenter = view.constrainCenter(newCenter);
  map.requestRenderFrame();
  view.setCenter(newCenter);
};


/**
 * @inheritDoc
 */
ol.interaction.DragPan.prototype.handleDragEnd = function(mapBrowserEvent) {

  // FIXME works for View2D only

  var map = mapBrowserEvent.map;
  var view = map.getView();
  view.setHint(ol.ViewHint.INTERACTING, -1);

  if (this.kinetic_ && this.kinetic_.end()) {
    var view2D = view.getView2D();
    goog.asserts.assertInstanceof(view2D, ol.View2D);
    var view2DState = view2D.getView2DState();
    var distance = this.kinetic_.getDistance();
    var angle = this.kinetic_.getAngle();
    this.kineticPreRenderFn_ = this.kinetic_.pan(view2DState.center);
    map.beforeRender(this.kineticPreRenderFn_);

    var centerpx = map.getPixelFromCoordinate(view2DState.center);
    var dest = map.getCoordinateFromPixel([
      centerpx[0] - distance * Math.cos(angle),
      centerpx[1] - distance * Math.sin(angle)
    ]);
    dest = view2D.constrainCenter(dest);
    view2D.setCenter(dest);
  }
  map.requestRenderFrame();
};


/**
 * @inheritDoc
 */
ol.interaction.DragPan.prototype.handleDragStart = function(mapBrowserEvent) {
  var browserEvent = mapBrowserEvent.browserEvent;
  if (browserEvent.isMouseActionButton() && this.condition_(mapBrowserEvent)) {
    if (this.kinetic_) {
      this.kinetic_.begin();
      this.kinetic_.update(browserEvent.clientX, browserEvent.clientY);
    }
    var map = mapBrowserEvent.map;
    map.getView().setHint(ol.ViewHint.INTERACTING, 1);
    map.requestRenderFrame();
    return true;
  } else {
    return false;
  }
};


/**
 * @inheritDoc
 */
ol.interaction.DragPan.prototype.handleDown = function(mapBrowserEvent) {
  var map = mapBrowserEvent.map;
  // FIXME works for View2D only
  var view = map.getView();
  goog.asserts.assertInstanceof(view, ol.View2D);
  goog.asserts.assert(!goog.isNull(mapBrowserEvent.frameState));
  if (!goog.isNull(this.kineticPreRenderFn_) &&
      map.removePreRenderFunction(this.kineticPreRenderFn_)) {
    map.requestRenderFrame();
    view.setCenter(mapBrowserEvent.frameState.view2DState.center);
    this.kineticPreRenderFn_ = null;
  }
};