// =====================================================================
// Accessibility helpers for Shaarli Pro modals and overlays.
// =====================================================================
(function (root) {
    'use strict';

    const FOCUSABLE_SELECTORS = [
        'a[href]',
        'button:not([disabled])',
        'input:not([disabled])',
        'select:not([disabled])',
        'textarea:not([disabled])',
        '[tabindex]:not([tabindex="-1"])'
    ].join(', ');

    /**
     * Return a focusable element inside a container.
     */
    function getFocusable(container, first) {
        if (!container) return null;
        const elements = Array.prototype.slice.call(container.querySelectorAll(FOCUSABLE_SELECTORS));
        return first ? elements[0] : elements[elements.length - 1];
    }

    /**
     * Move focus to the first focusable element inside a container.
     */
    function focusFirst(container) {
        const el = getFocusable(container, true);
        if (el) el.focus();
    }

    /**
     * Keep keyboard focus inside a container while it is open.
     * Returns a cleanup function that removes the listener.
     */
    function trapFocus(container) {
        if (!container) return function () {};

        function handleKey(e) {
            if (e.key !== 'Tab') return;
            const first = getFocusable(container, true);
            const last = getFocusable(container, false);
            if (!first || !last) return;

            if (e.shiftKey && document.activeElement === first) {
                e.preventDefault();
                last.focus();
            } else if (!e.shiftKey && document.activeElement === last) {
                e.preventDefault();
                first.focus();
            }
        }

        container.addEventListener('keydown', handleKey);
        return function () {
            container.removeEventListener('keydown', handleKey);
        };
    }

    root.ShaarliProA11y = {
        focusFirst: focusFirst,
        trapFocus: trapFocus,
        getFocusable: getFocusable
    };
}(window));