/**
 * Shared scroll lock for MeetLet modals.
 * Uses body overflow + scroll guards — no position:fixed on body (avoids white-page flash).
 *
 * @package    mod_meetletacbfree
 * @copyright  2026 MeetLet
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
(function (global) {
    'use strict';

    var scrollLockY = 0;
    var guardsActive = false;

    function scrollbarWidth() {
        return Math.max(0, global.innerWidth - document.documentElement.clientWidth);
    }

    function focusNoScroll(el) {
        if (!el || typeof el.focus !== 'function') {
            return;
        }
        try {
            el.focus({preventScroll: true});
        } catch (e) {
            el.focus();
        }
    }

    function restoreScroll() {
        if (scrollLockY > 0) {
            global.scrollTo(0, scrollLockY);
        }
    }

    function onScrollGuard() {
        if (scrollLockY && global.scrollY !== scrollLockY) {
            global.scrollTo(0, scrollLockY);
        }
    }

    function onMoveGuard(e) {
        if (e.target.closest && e.target.closest('.meetlet-modal__dialog')) {
            return;
        }
        e.preventDefault();
    }

    function bindGuards() {
        if (guardsActive) {
            return;
        }
        guardsActive = true;
        global.addEventListener('scroll', onScrollGuard, true);
        global.addEventListener('wheel', onMoveGuard, {passive: false, capture: true});
        global.addEventListener('touchmove', onMoveGuard, {passive: false, capture: true});
    }

    function unbindGuards() {
        if (!guardsActive) {
            return;
        }
        guardsActive = false;
        global.removeEventListener('scroll', onScrollGuard, true);
        global.removeEventListener('wheel', onMoveGuard, true);
        global.removeEventListener('touchmove', onMoveGuard, true);
    }

    function lockPageScroll() {
        if (document.documentElement.classList.contains('meetlet-modal-open')) {
            return;
        }
        scrollLockY = global.scrollY || document.documentElement.scrollTop || document.body.scrollTop || 0;
        var pad = scrollbarWidth();
        if (pad > 0) {
            document.body.style.paddingRight = pad + 'px';
        }
        document.documentElement.classList.add('meetlet-modal-open');
        restoreScroll();
        if (typeof global.requestAnimationFrame === 'function') {
            global.requestAnimationFrame(restoreScroll);
        }
        bindGuards();
    }

    function unlockPageScroll() {
        if (!document.documentElement.classList.contains('meetlet-modal-open')) {
            return;
        }
        unbindGuards();
        var y = scrollLockY;
        document.documentElement.classList.remove('meetlet-modal-open');
        document.body.style.paddingRight = '';
        scrollLockY = 0;
        if (y) {
            global.scrollTo(0, y);
            if (typeof global.requestAnimationFrame === 'function') {
                global.requestAnimationFrame(function () {
                    global.scrollTo(0, y);
                });
            }
        }
    }

    global.MeetletModalScroll = {
        lock: lockPageScroll,
        unlock: unlockPageScroll,
        focusNoScroll: focusNoScroll,
    };
}(typeof window !== 'undefined' ? window : this));