/**
 * filterCourses
 *
 * Filters table rows on the page based on the 'filter' parameter in the URL query string.
 * - Hides all table rows by default, then shows only rows whose text content matches any of the filter terms.
 * - Adds a heading and a "clear filter" link above the page's course listing heading to indicate filtering is active.
 * - Intended for use on pages with a heading containing 'Classes with Scheduled Trainings'.
 *
 * How it works:
 * 1. Parses the URL for a 'filter' parameter.
 * 2. Hides all <tr> elements.
 * 3. Shows only rows containing one or more of the filter terms.
 * 4. Annotates the page with filtering information and a way to clear the filter.
 *
 * Usage:
 * - Call this function after the DOM has loaded on pages where filtering should be enabled.
 * - Designed to work in conjunction with WordPress and the `CTF_FILTERABLE_COURSE` body class.
 */
function filterCourses(){
    //Get the URL query and create object
    let urlString = window.location.href;
    let paramString = urlString.split('?')[1];
    let queryString = new URLSearchParams(paramString);
    let params = {};
    for (let pair of queryString.entries()) {
        //console.log("Key is: " + pair[0]);
        //console.log("Value is: " + pair[1]);
        params[pair[0]] = pair[1].split(' ');
    }
    //console.log(params);
    if(params.filter === undefined){
        return;
    }

    //Find rows containing search term(s)
    let tableRows = document.getElementsByTagName('tr');
    let stack = [];
    for(let row of tableRows){
        stack.push(row)
        row.style = "display:none;";
    }
    let matches = [];
    while(stack.length > 0){
        let elem = stack.pop();
        //console.log(elem.textContent);
        for(let term of params.filter){
            if(elem.textContent.toLowerCase().includes(term.toLowerCase())){
                //textContent includes text in all children of node btw
                matches.push(elem);
            }
        }
        for(let child of elem.children){
            stack.push(child);
        }
    }
    //console.log(matches);
    for(let m of matches){
        //Unhide rows matching search criteria
        m.style ="";
    }

    //Get the page heading
    let pageHeading = undefined;
    for (const h2 of document.querySelectorAll('h2')) {
        if (h2.textContent.includes('Classes with Scheduled Trainings')) {
            pageHeading = h2;
            //console.log(pageHeading);
        }
    }

    //Create a heading on the page to indicate courses list is filtered.
    let filterLabel = document.createElement('h3');
    filterLabel.textContent = 'Filter: '+params.filter;
    let clearFilterButton = document.createElement('a');
    clearFilterButton.textContent = 'Click here to clear filter.';
    clearFilterButton.href = '.';
    pageHeading.before(filterLabel);
    pageHeading.before(clearFilterButton);
    pageHeading.before(document.createElement('hr'));
}
document.addEventListener('DOMContentLoaded',function(){
if(document.body.classList.contains('page-id-79')){
filterCourses();
}
});