// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * @module     mod_meetletacbfree/meetlet_modal_scroll
 * @copyright  2026 MeetLet <info@meetlet.net>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

define([], function() {
    'use strict';

    var scrollLockY = 0;
    var guardsActive = false;

    function scrollbarWidth() {
        return Math.max(0, window.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) {
            window.scrollTo(0, scrollLockY);
        }
    }

    function onScrollGuard() {
        if (scrollLockY && window.scrollY !== scrollLockY) {
            window.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;
        window.addEventListener('scroll', onScrollGuard, true);
        window.addEventListener('wheel', onMoveGuard, {passive: false, capture: true});
        window.addEventListener('touchmove', onMoveGuard, {passive: false, capture: true});
    }

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

    function lockPageScroll() {
        if (document.documentElement.classList.contains('meetlet-modal-open')) {
            return;
        }
        scrollLockY = window.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 window.requestAnimationFrame === 'function') {
            window.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) {
            window.scrollTo(0, y);
            if (typeof window.requestAnimationFrame === 'function') {
                window.requestAnimationFrame(function() {
                    window.scrollTo(0, y);
                });
            }
        }
    }

    return {
        init: function() {},
        lock: lockPageScroll,
        unlock: unlockPageScroll,
        focusNoScroll: focusNoScroll
    };
});