/*
 * L.PosAnimation is used by Leaflet internally for pan animations.
 */

L.PosAnimation = L.Class.extend({
	includes: L.Mixin.Events,

	run: function (el, newPos, duration, easeLinearity) { // (HTMLElement, Point[, Number, Number])
		this.stop();

		this._el = el;
		this._inProgress = true;
		this._newPos = newPos;

		this.fire('start');

		el.style[L.DomUtil.TRANSITION] = 'all ' + (duration || 0.25) +
		        's cubic-bezier(0,0,' + (easeLinearity || 0.5) + ',1)';

		L.DomEvent.on(el, L.DomUtil.TRANSITION_END, this._onTransitionEnd, this);
		L.DomUtil.setPosition(el, newPos);

		// toggle reflow, Chrome flickers for some reason if you don't do this
		L.Util.falseFn(el.offsetWidth);

		// there's no native way to track value updates of transitioned properties, so we imitate this
		this._stepTimer = setInterval(L.bind(this._onStep, this), 50);
	},

	stop: function () {
		if (!this._inProgress) { return; }

		// if we just removed the transition property, the element would jump to its final position,
		// so we need to make it stay at the current position

		L.DomUtil.setPosition(this._el, this._getPos());
		this._onTransitionEnd();
		L.Util.falseFn(this._el.offsetWidth); // force reflow in case we are about to start a new animation
	},

	_onStep: function () {
		var stepPos = this._getPos();
		if (!stepPos) {
			this._onTransitionEnd();
			return;
		}
		// jshint camelcase: false
		// make L.DomUtil.getPosition return intermediate position value during animation
		this._el._leaflet_pos = stepPos;

		this.fire('step');
	},

	// you can't easily get intermediate values of properties animated with CSS3 Transitions,
	// we need to parse computed style (in case of transform it returns matrix string)

	_transformRe: /([-+]?(?:\d*\.)?\d+)\D*, ([-+]?(?:\d*\.)?\d+)\D*\)/,

	_getPos: function () {
		var left, top, matches,
		    el = this._el,
		    style = window.getComputedStyle(el);

		if (L.Browser.any3d) {
			matches = style[L.DomUtil.TRANSFORM].match(this._transformRe);
			if (!matches) { return; }
			left = parseFloat(matches[1]);
			top  = parseFloat(matches[2]);
		} else {
			left = parseFloat(style.left);
			top  = parseFloat(style.top);
		}

		return new L.Point(left, top, true);
	},

	_onTransitionEnd: function () {
		L.DomEvent.off(this._el, L.DomUtil.TRANSITION_END, this._onTransitionEnd, this);

		if (!this._inProgress) { return; }
		this._inProgress = false;

		this._el.style[L.DomUtil.TRANSITION] = '';

		// jshint camelcase: false
		// make sure L.DomUtil.getPosition returns the final position value after animation
		this._el._leaflet_pos = this._newPos;

		clearInterval(this._stepTimer);

		this.fire('step').fire('end');
	}

});
