lazyLoadAssets()

nebula.lazyLoadAssets = async function(){
    nebula.site.resources.lazy.promises = {};

    //Detect if Bootstrap JS is needed and load it
    //A wildcard attribute name selector would be super useful here, but does not exist. Something like [data-bs-*] would be perfect...
    //That being said, the Offcanvas component will be used on 95% of Nebula sites, so this will likely load on every page regardless.
    if ( jQuery('.offcanvas, .accordion, .alert, .carousel, .collapse, .dropdown-menu, .modal, .nav-tabs, .nav-pills').length ){
        nebula.loadJS(nebula.site.resources.scripts['nebula_bootstrap']); //Load Bootstrap JS
    }

    //Lazy load elements as they scroll into viewport
    try {
        //Observe the entries that are identified and added later (below)
        let lazyObserver = new IntersectionObserver(function(entries){
            entries.forEach(function(entry){
                if ( entry.intersectionRatio > 0 ){
                    nebula.loadElement(jQuery(entry.target));
                    lazyObserver.unobserve(entry.target); //Stop observing the element
                }
            });
        }, {
            rootMargin: '50%', //Extend the area of the observer (100% = Double the Viewport). Try to prevent visible loading of elements by triggering the load much earlier than actually needed.
            threshold: 0.1
        });

        //Create the entries and add them to the observer
        jQuery('.nebula-lazy-position, .lazy-load').each(function(){
            lazyObserver.observe(jQuery(this)[0]); //Observe the element
        });

        //When scroll reaches the bottom, ensure everything has loaded at this point
        //Only when IntersectionObserver exists because otherwise everything is immediately loaded anyway
        let lazyLoadScrollBottom = function(){
            if( nebula.dom.window.scrollTop()+nebula.dom.window.height() > nebula.dom.document.height()-500 ){ //When the scroll position reaches 500px above the bottom
                nebula.loadEverything();
                window.removeEventListener('scroll', lazyLoadScrollBottom); //Stop listening for this scroll event
            }
        };
        window.addEventListener('scroll', lazyLoadScrollBottom); //Scroll is passive by default
    } catch(error){
        nebula.loadEverything(); //If any error, load everything immediately
        nebula.help('Lazy Load Observer: ' + error + '. All assets have been loaded immediately.', '/functions/lazyloadassets/', true);
    }

    //Load all lazy elements at once if requested
    nebula.dom.window.on('nebula_load', function(){
        if ( typeof window.requestIdleCallback === 'function' ){ //If requestIdleCallback exists, use it. Remove this check when Safari supports it
            window.requestIdleCallback(function(){
                nebula.loadEverything();
            });
        } else { //Otherwise, just run immediately
            nebula.loadEverything();
        }
    });

    //Lazy load CSS assets
    //Listen for requestIdleCallback here when Safari supports it
    jQuery.each(nebula.site.resources.lazy.styles, function(handle, condition){
        if ( condition === 'all' || jQuery(condition).length ){
            if ( nebula.site.resources.styles[handle.replaceAll('-', '_')] ){ //If that handle exists in the registered styles
                nebula.loadCSS(nebula.site.resources.styles[handle.replaceAll('-', '_')]);
            }
        }
    });

    //Lazy load JS assets
    //Listen for requestIdleCallback here when Safari supports it
    jQuery.each(nebula.site.resources.lazy.scripts, function(handle, condition){
        if ( condition === 'all' || jQuery(condition).length ){
            if ( nebula.site.resources.scripts[handle.replaceAll('-', '_')] ){ //If that handle exists in the registered scripts
                nebula.loadJS(nebula.site.resources.scripts[handle.replaceAll('-', '_')], handle); //Load it (with a Promise)
            }
        }
    });

    //Load the Google Maps API if 'googlemap' class exists
    if ( jQuery('.googlemap').length ){
        if ( google?.maps ){ //If the API has not already been called
            nebula.loadJS('https://www.google.com/jsapi?key=' + nebula.site.options.nebula_google_browser_api_key, 'google-maps').then(function(){ //May not need key here, but just to be safe.
                google.load('maps', '3', {
                    other_params: 'libraries=places&key=' + nebula.site.options.nebula_google_browser_api_key,
                    callback: function(){
                        nebula.dom.document.trigger('nebula_google_maps_api_loaded');
                    }
                });
            });
        } else {
            nebula.dom.document.trigger('nebula_google_maps_api_loaded'); //Already loaded
        }
    }

    if ( jQuery('pre.nebula-code, pre.nebula-code').length ){
        nebula.loadCSS(nebula.site.resources.styles.nebula_pre);
        nebula.pre();
    }
};

nebula.lazyLoadAssets = function(){
    //Write your own code here, leave it blank, or return false.
}