document.addEventListener("DOMContentLoaded", function () {
    initDropdownMenu();
});

function initDropdownMenu() {
    const dropdown = document.querySelector('.dropdown');
    const menuItems = document.querySelectorAll('[role="menuitem"]');
    const menuButton = dropdown.querySelector('[role="button"]');

    dropdown.addEventListener("toggle", handleToggle.bind(null, dropdown, menuItems, menuButton));
    document.addEventListener("keydown", handleKeydown.bind(null, dropdown, menuItems, menuButton));
}

function handleToggle(dropdown, menuItems, menuButton) {
    if (dropdown.hasAttribute('open')) {
        focusMenuItem(menuItems, 0);
        setAriaExpanded(menuButton, true);
    } else {
        menuButton.focus();
        setAriaExpanded(menuButton, false);
    }
}

function handleKeydown(dropdown, menuItems, menuButton, event) {
    if (!dropdown.hasAttribute('open')) return;

    let focusedItemIndex = Array.from(menuItems).indexOf(document.activeElement);

    switch (event.key) {
        case "ArrowDown":
            event.preventDefault();
            focusMenuItem(menuItems, (focusedItemIndex + 1) % menuItems.length);
            break;
        case "ArrowUp":
            event.preventDefault();
            focusMenuItem(menuItems, (focusedItemIndex - 1 + menuItems.length) % menuItems.length);
            break;
        case "Escape":
            dropdown.removeAttribute('open');
            setAriaExpanded(menuButton, false);
            menuButton.focus();
            break;
    }
}

function focusMenuItem(menuItems, index) {
    menuItems[index].focus();
}

function setAriaExpanded(element, state) {
    element.setAttribute('aria-expanded', state ? 'true' : 'false');
}