theme-toggle.js

(function () {
    // --- THEME LOGIC ---
    const LIGHT = 'light';
    const DARK = 'ayu';
    const STORAGE_KEY = 'mdbook-theme';

    function getStoredTheme() {
        return (
            localStorage.getItem(STORAGE_KEY) ||
            (window.matchMedia('(prefers-color-scheme: dark)').matches ? DARK : LIGHT)
        );
    }

    function applyTheme(theme) {
        document.documentElement.classList.remove(LIGHT, DARK);
        document.documentElement.classList.add(theme);
        localStorage.setItem(STORAGE_KEY, theme);
    }

    function switchTheme() {
        const next = getStoredTheme() === LIGHT ? DARK : LIGHT;
        applyTheme(next);
    }

    function insertToggleButton() {
        const menuBar = document.getElementById('menu-bar');
        if (!menuBar) return;
        const toggleButton = document.createElement('button');
        toggleButton.id = 'custom-theme-toggle';
        toggleButton.type = 'button';
        toggleButton.innerHTML = '<i class="fa fa-sun-o light-mode" aria-hidden="true"></i><i class="fa fa-moon-o dark-mode" aria-hidden="true"></i>';
        toggleButton.addEventListener('click', switchTheme);

        const rightButtons = menuBar.querySelector('.right-buttons');
        (rightButtons || menuBar).prepend(toggleButton);
    }

    // --- EXTERNAL LINK LOGIC ---
    function patchExternalLinks() {
        document.querySelectorAll('a[href^="http"]').forEach(link => {
            if (!link.href.startsWith(window.location.origin)) {
                link.setAttribute('target', '_blank');
                link.setAttribute('rel', 'noopener noreferrer');
            }
        });
    }

    // --- INIT ---
    document.addEventListener('DOMContentLoaded', function () {
        applyTheme(getStoredTheme());
        insertToggleButton();
        patchExternalLinks();
    });
})();