(function(window, factory) {
    var lazySizes = factory(window, window.document, Date);
    window.lazySizes = lazySizes;
    if(typeof module == 'object' && module.exports){
        module.exports = lazySizes;
    }
}(typeof window != 'undefined' ?
    window : {}, function l(window, document, Date) { // Pass in the windoe Date function also for SSR because the Date class can be lost
        'use strict';
        /*jshint eqnull:true */

        var lazysizes, lazySizesCfg;

        (function(){
            var prop;

            var lazySizesDefaults = {
                lazyClass: 'lazyload',
                loadedClass: 'lazyloaded',
                loadingClass: 'lazyloading',
                preloadClass: 'lazypreload',
                errorClass: 'lazyerror',
                //strictClass: 'lazystrict',
                autosizesClass: 'lazyautosizes',
                srcAttr: 'data-src',
                srcsetAttr: 'data-srcset',
                sizesAttr: 'data-sizes',
                //preloadAfterLoad: false,
                minSize: 40,
                customMedia: {},
                init: true,
                expFactor: 1.5,
                hFac: 0.8,
                loadMode: 2,
                loadHidden: true,
                ricTimeout: 0,
                throttleDelay: 125,
            };

            lazySizesCfg = window.lazySizesConfig || window.lazysizesConfig || {};

            for(prop in lazySizesDefaults){
                if(!(prop in lazySizesCfg)){
                    lazySizesCfg[prop] = lazySizesDefaults[prop];
                }
            }
        })();

        if (!document || !document.getElementsByClassName) {
            return {
                init: function () {},
                cfg: lazySizesCfg,
                noSupport: true,
            };
        }

        var docElem = document.documentElement;

        var supportPicture = window.HTMLPictureElement;

        var _addEventListener = 'addEventListener';

        var _getAttribute = 'getAttribute';

        /**
         * Update to bind to window because 'this' becomes null during SSR
         * builds.
         */
        var addEventListener = window[_addEventListener].bind(window);

        var setTimeout = window.setTimeout;

        var requestAnimationFrame = window.requestAnimationFrame || setTimeout;

        var requestIdleCallback = window.requestIdleCallback;

        var regPicture = /^picture$/i;

        var loadEvents = ['load', 'error', 'lazyincluded', '_lazyloaded'];

        var regClassCache = {};

        var forEach = Array.prototype.forEach;

        var hasClass = function(ele, cls) {
            if(!regClassCache[cls]){
                regClassCache[cls] = new RegExp('(\\s|^)'+cls+'(\\s|$)');
            }
            return regClassCache[cls].test(ele[_getAttribute]('class') || '') && regClassCache[cls];
        };

        var addClass = function(ele, cls) {
            if (!hasClass(ele, cls)){
                ele.setAttribute('class', (ele[_getAttribute]('class') || '').trim() + ' ' + cls);
            }
        };

        var removeClass = function(ele, cls) {
            var reg;
            if ((reg = hasClass(ele,cls))) {
                ele.setAttribute('class', (ele[_getAttribute]('class') || '').replace(reg, ' '));
            }
        };

        var addRemoveLoadEvents = function(dom, fn, add){
            var action = add ? _addEventListener : 'removeEventListener';
            if(add){
                addRemoveLoadEvents(dom, fn);
            }
            loadEvents.forEach(function(evt){
                dom[action](evt, fn);
            });
        };

        var triggerEvent = function(elem, name, detail, noBubbles, noCancelable){
            var event = document.createEvent('Event');

            if(!detail){
                detail = {};
            }

            detail.instance = lazysizes;

            event.initEvent(name, !noBubbles, !noCancelable);

            event.detail = detail;

            elem.dispatchEvent(event);
            return event;
        };

        var updatePolyfill = function (el, full){
            var polyfill;
            if( !supportPicture && ( polyfill = (window.picturefill || lazySizesCfg.pf) ) ){
                if(full && full.src && !el[_getAttribute]('srcset')){
                    el.setAttribute('srcset', full.src);
                }
                polyfill({reevaluate: true, elements: [el]});
            } else if(full && full.src){
                el.src = full.src;
            }
        };

        var getCSS = function (elem, style){
            return (getComputedStyle(elem, null) || {})[style];
        };

        var getWidth = function(elem, parent, width){
            width = width || elem.offsetWidth;

            while(width < lazySizesCfg.minSize && parent && !elem._lazysizesWidth){
                width =  parent.offsetWidth;
                parent = parent.parentNode;
            }

            return width;
        };

        var rAF = (function(){
            var running, waiting;
            var firstFns = [];
            var secondFns = [];
            var fns = firstFns;

            var run = function(){
                var runFns = fns;

                fns = firstFns.length ? secondFns : firstFns;

                running = true;
                waiting = false;

                while(runFns.length){
                    runFns.shift()();
                }

                running = false;
            };

            var rafBatch = function(fn, queue){
                if(running && !queue){
                    fn.apply(this, arguments);
                } else {
                    fns.push(fn);

                    if(!waiting){
                        waiting = true;
                        (document.hidden ? setTimeout : requestAnimationFrame)(run);
                    }
                }
            };

            rafBatch._lsFlush = run;

            return rafBatch;
        })();

        var rAFIt = function(fn, simple){
            return simple ?
                function() {
                    rAF(fn);
                } :
                function(){
                    var that = this;
                    var args = arguments;
                    rAF(function(){
                        fn.apply(that, args);
                    });
                }
                ;
        };

        var throttle = function(fn){
            var running;
            var lastTime = 0;
            var gDelay = lazySizesCfg.throttleDelay;
            var rICTimeout = lazySizesCfg.ricTimeout;
            var run = function(){
                running = false;
                lastTime = Date.now();
                fn();
            };
            var idleCallback = requestIdleCallback && rICTimeout > 49 ?
                function(){
                    requestIdleCallback(run, {timeout: rICTimeout});

                    if(rICTimeout !== lazySizesCfg.ricTimeout){
                        rICTimeout = lazySizesCfg.ricTimeout;
                    }
                } :
                rAFIt(function(){
                    setTimeout(run);
                }, true)
            ;

            return function(isPriority){
                var delay;

                if((isPriority = isPriority === true)){
                    rICTimeout = 33;
                }

                if(running){
                    return;
                }

                running =  true;

                delay = gDelay - (Date.now() - lastTime);

                if(delay < 0){
                    delay = 0;
                }

                if(isPriority || delay < 9){
                    idleCallback();
                } else {
                    setTimeout(idleCallback, delay);
                }
            };
        };

        //based on http://modernjavascript.blogspot.de/2013/08/building-better-debounce.html
        var debounce = function(func) {
            var timeout, timestamp;
            var wait = 99;
            var run = function(){
                timeout = null;
                func();
            };
            var later = function() {
                var last = Date.now() - timestamp;

                if (last < wait) {
                    setTimeout(later, wait - last);
                } else {
                    (requestIdleCallback || run)(run);
                }
            };

            return function() {
                timestamp = Date.now();

                if (!timeout) {
                    timeout = setTimeout(later, wait);
                }
            };
        };

        var loader = (function(){
            var preloadElems, isCompleted, resetPreloadingTimer, loadMode, started;

            var eLvW, elvH, eLtop, eLleft, eLright, eLbottom, isBodyHidden;

            var regImg = /^img$/i;
            var regIframe = /^iframe$/i;

            var supportScroll = ('onscroll' in window) && !(/(gle|ing)bot/.test(navigator.userAgent));

            var shrinkExpand = 0;
            var currentExpand = 0;

            var isLoading = 0;
            var lowRuns = -1;

            var resetPreloading = function(e){
                isLoading--;
                if(!e || isLoading < 0 || !e.target){
                    isLoading = 0;
                }
            };

            var isVisible = function (elem) {
                if (isBodyHidden == null) {
                    isBodyHidden = getCSS(document.body, 'visibility') == 'hidden';
                }

                return isBodyHidden || !(getCSS(elem.parentNode, 'visibility') == 'hidden' && getCSS(elem, 'visibility') == 'hidden');
            };

            var isNestedVisible = function(elem, elemExpand){
                var outerRect;
                var parent = elem;
                var visible = isVisible(elem);

                eLtop -= elemExpand;
                eLbottom += elemExpand;
                eLleft -= elemExpand;
                eLright += elemExpand;

                while(visible && (parent = parent.offsetParent) && parent != document.body && parent != docElem){
                    visible = ((getCSS(parent, 'opacity') || 1) > 0);

                    if(visible && getCSS(parent, 'overflow') != 'visible'){
                        outerRect = parent.getBoundingClientRect();
                        visible = eLright > outerRect.left &&
                            eLleft < outerRect.right &&
                            eLbottom > outerRect.top - 1 &&
                            eLtop < outerRect.bottom + 1
                        ;
                    }
                }

                return visible;
            };

            var checkElements = function() {
                var eLlen, i, rect, autoLoadElem, loadedSomething, elemExpand, elemNegativeExpand, elemExpandVal,
                    beforeExpandVal, defaultExpand, preloadExpand, hFac;
                var lazyloadElems = lazysizes.elements;

                if((loadMode = lazySizesCfg.loadMode) && isLoading < 8 && (eLlen = lazyloadElems.length)){

                    i = 0;

                    lowRuns++;

                    for(; i < eLlen; i++){

                        if(!lazyloadElems[i] || lazyloadElems[i]._lazyRace){continue;}

                        if(!supportScroll || (lazysizes.prematureUnveil && lazysizes.prematureUnveil(lazyloadElems[i]))){unveilElement(lazyloadElems[i]);continue;}

                        if(!(elemExpandVal = lazyloadElems[i][_getAttribute]('data-expand')) || !(elemExpand = elemExpandVal * 1)){
                            elemExpand = currentExpand;
                        }

                        if (!defaultExpand) {
                            defaultExpand = (!lazySizesCfg.expand || lazySizesCfg.expand < 1) ?
                                docElem.clientHeight > 500 && docElem.clientWidth > 500 ? 500 : 370 :
                                lazySizesCfg.expand;

                            lazysizes._defEx = defaultExpand;

                            preloadExpand = defaultExpand * lazySizesCfg.expFactor;
                            hFac = lazySizesCfg.hFac;
                            isBodyHidden = null;

                            if(currentExpand < preloadExpand && isLoading < 1 && lowRuns > 2 && loadMode > 2 && !document.hidden){
                                currentExpand = preloadExpand;
                                lowRuns = 0;
                            } else if(loadMode > 1 && lowRuns > 1 && isLoading < 6){
                                currentExpand = defaultExpand;
                            } else {
                                currentExpand = shrinkExpand;
                            }
                        }

                        if(beforeExpandVal !== elemExpand){
                            eLvW = innerWidth + (elemExpand * hFac);
                            elvH = innerHeight + elemExpand;
                            elemNegativeExpand = elemExpand * -1;
                            beforeExpandVal = elemExpand;
                        }

                        rect = lazyloadElems[i].getBoundingClientRect();

                        if ((eLbottom = rect.bottom) >= elemNegativeExpand &&
                            (eLtop = rect.top) <= elvH &&
                            (eLright = rect.right) >= elemNegativeExpand * hFac &&
                            (eLleft = rect.left) <= eLvW &&
                            (eLbottom || eLright || eLleft || eLtop) &&
                            (lazySizesCfg.loadHidden || isVisible(lazyloadElems[i])) &&
                            ((isCompleted && isLoading < 3 && !elemExpandVal && (loadMode < 3 || lowRuns < 4)) || isNestedVisible(lazyloadElems[i], elemExpand))){
                            unveilElement(lazyloadElems[i]);
                            loadedSomething = true;
                            if(isLoading > 9){break;}
                        } else if(!loadedSomething && isCompleted && !autoLoadElem &&
                            isLoading < 4 && lowRuns < 4 && loadMode > 2 &&
                            (preloadElems[0] || lazySizesCfg.preloadAfterLoad) &&
                            (preloadElems[0] || (!elemExpandVal && ((eLbottom || eLright || eLleft || eLtop) || lazyloadElems[i][_getAttribute](lazySizesCfg.sizesAttr) != 'auto')))){
                            autoLoadElem = preloadElems[0] || lazyloadElems[i];
                        }
                    }

                    if(autoLoadElem && !loadedSomething){
                        unveilElement(autoLoadElem);
                    }
                }
            };

            var throttledCheckElements = throttle(checkElements);

            var switchLoadingClass = function(e){
                var elem = e.target;

                if (elem._lazyCache) {
                    delete elem._lazyCache;
                    return;
                }

                resetPreloading(e);
                addClass(elem, lazySizesCfg.loadedClass);
                removeClass(elem, lazySizesCfg.loadingClass);
                addRemoveLoadEvents(elem, rafSwitchLoadingClass);
                triggerEvent(elem, 'lazyloaded');
            };
            var rafedSwitchLoadingClass = rAFIt(switchLoadingClass);
            var rafSwitchLoadingClass = function(e){
                rafedSwitchLoadingClass({target: e.target});
            };

            var changeIframeSrc = function(elem, src){
                try {
                    elem.contentWindow.location.replace(src);
                } catch(e){
                    elem.src = src;
                }
            };

            var handleSources = function(source){
                var customMedia;

                var sourceSrcset = source[_getAttribute](lazySizesCfg.srcsetAttr);

                if( (customMedia = lazySizesCfg.customMedia[source[_getAttribute]('data-media') || source[_getAttribute]('media')]) ){
                    source.setAttribute('media', customMedia);
                }

                if(sourceSrcset){
                    source.setAttribute('srcset', sourceSrcset);
                }
            };

            var lazyUnveil = rAFIt(function (elem, detail, isAuto, sizes, isImg){
                var src, srcset, parent, isPicture, event, firesLoad;

                if(!(event = triggerEvent(elem, 'lazybeforeunveil', detail)).defaultPrevented){

                    if(sizes){
                        if(isAuto){
                            addClass(elem, lazySizesCfg.autosizesClass);
                        } else {
                            elem.setAttribute('sizes', sizes);
                        }
                    }

                    srcset = elem[_getAttribute](lazySizesCfg.srcsetAttr);
                    src = elem[_getAttribute](lazySizesCfg.srcAttr);

                    if(isImg) {
                        parent = elem.parentNode;
                        isPicture = parent && regPicture.test(parent.nodeName || '');
                    }

                    firesLoad = detail.firesLoad || (('src' in elem) && (srcset || src || isPicture));

                    event = {target: elem};

                    addClass(elem, lazySizesCfg.loadingClass);

                    if(firesLoad){
                        clearTimeout(resetPreloadingTimer);
                        resetPreloadingTimer = setTimeout(resetPreloading, 2500);
                        addRemoveLoadEvents(elem, rafSwitchLoadingClass, true);
                    }

                    if(isPicture){
                        forEach.call(parent.getElementsByTagName('source'), handleSources);
                    }

                    if(srcset){
                        elem.setAttribute('srcset', srcset);
                    } else if(src && !isPicture){
                        if(regIframe.test(elem.nodeName)){
                            changeIframeSrc(elem, src);
                        } else {
                            elem.src = src;
                        }
                    }

                    if(isImg && (srcset || isPicture)){
                        updatePolyfill(elem, {src: src});
                    }
                }

                if(elem._lazyRace){
                    delete elem._lazyRace;
                }
                removeClass(elem, lazySizesCfg.lazyClass);

                rAF(function(){
                    // Part of this can be removed as soon as this fix is older: https://bugs.chromium.org/p/chromium/issues/detail?id=7731 (2015)
                    var isLoaded = elem.complete && elem.naturalWidth > 1;

                    if( !firesLoad || isLoaded){
                        if (isLoaded) {
                            addClass(elem, 'ls-is-cached');
                        }
                        switchLoadingClass(event);
                        elem._lazyCache = true;
                        setTimeout(function(){
                            if ('_lazyCache' in elem) {
                                delete elem._lazyCache;
                            }
                        }, 9);
                    }
                    if (elem.loading == 'lazy') {
                        isLoading--;
                    }
                }, true);
            });

            var unveilElement = function (elem){
                if (elem._lazyRace) {return;}
                var detail;

                var isImg = regImg.test(elem.nodeName);

                //allow using sizes="auto", but don't use. it's invalid. Use data-sizes="auto" or a valid value for sizes instead (i.e.: sizes="80vw")
                var sizes = isImg && (elem[_getAttribute](lazySizesCfg.sizesAttr) || elem[_getAttribute]('sizes'));
                var isAuto = sizes == 'auto';

                if( (isAuto || !isCompleted) && isImg && (elem[_getAttribute]('src') || elem.srcset) && !elem.complete && !hasClass(elem, lazySizesCfg.errorClass) && hasClass(elem, lazySizesCfg.lazyClass)){return;}

                detail = triggerEvent(elem, 'lazyunveilread').detail;

                if(isAuto){
                    autoSizer.updateElem(elem, true, elem.offsetWidth);
                }

                elem._lazyRace = true;
                isLoading++;

                lazyUnveil(elem, detail, isAuto, sizes, isImg);
            };

            var afterScroll = debounce(function(){
                lazySizesCfg.loadMode = 3;
                throttledCheckElements();
            });

            var altLoadmodeScrollListner = function(){
                if(lazySizesCfg.loadMode == 3){
                    lazySizesCfg.loadMode = 2;
                }
                afterScroll();
            };

            var onload = function(){
                if(isCompleted){return;}
                if(Date.now() - started < 999){
                    setTimeout(onload, 999);
                    return;
                }


                isCompleted = true;

                lazySizesCfg.loadMode = 3;

                throttledCheckElements();

                addEventListener('scroll', altLoadmodeScrollListner, true);
            };

            return {
                _: function(){
                    started = Date.now();

                    lazysizes.elements = document.getElementsByClassName(lazySizesCfg.lazyClass);
                    preloadElems = document.getElementsByClassName(lazySizesCfg.lazyClass + ' ' + lazySizesCfg.preloadClass);

                    addEventListener('scroll', throttledCheckElements, true);

                    addEventListener('resize', throttledCheckElements, true);

                    addEventListener('pageshow', function (e) {
                        if (e.persisted) {
                            var loadingElements = document.querySelectorAll('.' + lazySizesCfg.loadingClass);

                            if (loadingElements.length && loadingElements.forEach) {
                                requestAnimationFrame(function () {
                                    loadingElements.forEach( function (img) {
                                        if (img.complete) {
                                            unveilElement(img);
                                        }
                                    });
                                });
                            }
                        }
                    });

                    if(window.MutationObserver){
                        new MutationObserver( throttledCheckElements ).observe( docElem, {childList: true, subtree: true, attributes: true} );
                    } else {
                        docElem[_addEventListener]('DOMNodeInserted', throttledCheckElements, true);
                        docElem[_addEventListener]('DOMAttrModified', throttledCheckElements, true);
                        setInterval(throttledCheckElements, 999);
                    }

                    addEventListener('hashchange', throttledCheckElements, true);

                    //, 'fullscreenchange'
                    ['focus', 'mouseover', 'click', 'load', 'transitionend', 'animationend'].forEach(function(name){
                        document[_addEventListener](name, throttledCheckElements, true);
                    });

                    if((/d$|^c/.test(document.readyState))){
                        onload();
                    } else {
                        addEventListener('load', onload);
                        document[_addEventListener]('DOMContentLoaded', throttledCheckElements);
                        setTimeout(onload, 20000);
                    }

                    if(lazysizes.elements.length){
                        checkElements();
                        rAF._lsFlush();
                    } else {
                        throttledCheckElements();
                    }
                },
                checkElems: throttledCheckElements,
                unveil: unveilElement,
                _aLSL: altLoadmodeScrollListner,
            };
        })();


        var autoSizer = (function(){
            var autosizesElems;

            var sizeElement = rAFIt(function(elem, parent, event, width){
                var sources, i, len;
                elem._lazysizesWidth = width;
                width += 'px';

                elem.setAttribute('sizes', width);

                if(regPicture.test(parent.nodeName || '')){
                    sources = parent.getElementsByTagName('source');
                    for(i = 0, len = sources.length; i < len; i++){
                        sources[i].setAttribute('sizes', width);
                    }
                }

                if(!event.detail.dataAttr){
                    updatePolyfill(elem, event.detail);
                }
            });
            var getSizeElement = function (elem, dataAttr, width){
                var event;
                var parent = elem.parentNode;

                if(parent){
                    width = getWidth(elem, parent, width);
                    event = triggerEvent(elem, 'lazybeforesizes', {width: width, dataAttr: !!dataAttr});

                    if(!event.defaultPrevented){
                        width = event.detail.width;

                        if(width && width !== elem._lazysizesWidth){
                            sizeElement(elem, parent, event, width);
                        }
                    }
                }
            };

            var updateElementsSizes = function(){
                var i;
                var len = autosizesElems.length;
                if(len){
                    i = 0;

                    for(; i < len; i++){
                        getSizeElement(autosizesElems[i]);
                    }
                }
            };

            var debouncedUpdateElementsSizes = debounce(updateElementsSizes);

            return {
                _: function(){
                    autosizesElems = document.getElementsByClassName(lazySizesCfg.autosizesClass);
                    addEventListener('resize', debouncedUpdateElementsSizes);
                },
                checkElems: debouncedUpdateElementsSizes,
                updateElem: getSizeElement
            };
        })();

        var init = function(){
            if(!init.i && document.getElementsByClassName){
                init.i = true;
                autoSizer._();
                loader._();
            }
        };

        setTimeout(function(){
            if(lazySizesCfg.init){
                init();
            }
        });

        lazysizes = {
            cfg: lazySizesCfg,
            autoSizer: autoSizer,
            loader: loader,
            init: init,
            uP: updatePolyfill,
            aC: addClass,
            rC: removeClass,
            hC: hasClass,
            fire: triggerEvent,
            gW: getWidth,
            rAF: rAF,
        };

        return lazysizes;
    }
));