website/js/main.js

document.addEventListener('DOMContentLoaded', ready, false);

const THEME_PREF_STORAGE_KEY = "theme-preference";
const THEME_TO_ICON_CLASS = {
    'dark': 'feather-moon',
    'light':'feather-sun'
};
const THEME_TO_ICON_TEXT_CLASS = {
    'dark': 'Dark mode',
    'light':'Light mode'
};
let toggleIcon = '';
let darkThemeCss = '';

const HEADING_TO_TOC_CLASS = {
    'H1': 'level-1',
    'H2': 'level-2',
    'H3': 'level-3',
    'H4': 'level-4'
}

function ready() {
    feather.replace({ 'stroke-width': 1, width: 20, height: 20 });
    setThemeByUserPref();

    if (document.querySelector('main#content > .container') !== null &&
            document.querySelector('main#content > .container').classList.contains('post')) {
        if (document.getElementById('TableOfContents') !== null) {
            fixTocItemsIndent();
            addSmoothScroll();
            createScrollSpy();
        } else {
            document.querySelector('main#content > .container.post').style.display = "block";
        }
    }

    // Elements to inject
    const svgsToInject = document.querySelectorAll('img.svg-inject');
    // Do the injection
    SVGInjector(svgsToInject);

    document.getElementById('hamburger-menu-toggle').addEventListener('click', () => {
        const hamburgerMenu = document.getElementsByClassName('nav-hamburger-list')[0]
        if (hamburgerMenu.classList.contains('visibility-hidden')) {
            hamburgerMenu.classList.remove('visibility-hidden');
        } else {
            hamburgerMenu.classList.add('visibility-hidden');
        }
    })
}

window.addEventListener('scroll', () => {
    if (window.innerWidth <= 820) {
        // For smaller screen, show shadow earlier
        toggleHeaderShadow(50);
    } else {
        toggleHeaderShadow(100);
    }
});

function fixTocItemsIndent() {
    document.querySelectorAll('#TableOfContents a').forEach($tocItem => {
      const itemId = $tocItem.getAttribute("href").substring(1)
      $tocItem.classList.add(HEADING_TO_TOC_CLASS[document.getElementById(itemId).tagName]);
    });
}

function addSmoothScroll() {
    document.querySelectorAll('#toc a').forEach($anchor => {
        $anchor.addEventListener('click', function (e) {
            e.preventDefault();
            document.getElementById(this.getAttribute('href').substring(1)).scrollIntoView({
                behavior: 'smooth',
                block: 'start' //scroll to top of the target element
            });
        });
    });
}

function createScrollSpy() {
    var elements = document.querySelectorAll('#toc a');
    document.addEventListener('scroll', function () {
        elements.forEach(function (element) {
          const boundingRect = document.getElementById(element.getAttribute('href').substring(1)).getBoundingClientRect();
          if (boundingRect.top <= 55 && boundingRect.bottom >= 0) {
            elements.forEach(function (elem) {
              elem.classList.remove('active');
            });
            element.classList.add('active');
          }
        });
    });
}

function toggleHeaderShadow(scrollY) {
    if (window.scrollY > scrollY) {
        document.querySelectorAll('.header').forEach(function(item) {
            item.classList.add('header-shadow')
        })
    } else {
        document.querySelectorAll('.header').forEach(function(item) {
            item.classList.remove('header-shadow')
        })
    }
}

function setThemeByUserPref() {
    darkThemeCss = document.getElementById("dark-theme");
    const savedTheme = localStorage.getItem(THEME_PREF_STORAGE_KEY) ||
        (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark': 'light');
    const darkThemeToggles = document.querySelectorAll('.dark-theme-toggle');
    setTheme(savedTheme, darkThemeToggles);
    darkThemeToggles.forEach(el => el.addEventListener('click', (event) => {
        toggleIcon = event.currentTarget.querySelector("a svg.feather");
        if (toggleIcon.classList[1] === THEME_TO_ICON_CLASS.dark) {
            setTheme('light', [event.currentTarget]);
        } else if (toggleIcon.classList[1] === THEME_TO_ICON_CLASS.light) {
            setTheme('dark', [event.currentTarget]);
        }
    }));
}

function setTheme(themeToSet, targets) {
    localStorage.setItem(THEME_PREF_STORAGE_KEY, themeToSet);
    darkThemeCss.disabled = themeToSet === 'light';
    targets.forEach((target) => {
        target.querySelector('a').innerHTML = feather.icons[THEME_TO_ICON_CLASS[themeToSet].split('-')[1]].toSvg();
        target.querySelector("#dark-theme-toggle-screen-reader-target").textContent = [THEME_TO_ICON_TEXT_CLASS[themeToSet]];
    });
}