1 files changed, 88 insertions, 0 deletions
diff --git a/site/themes/sine/static/js/switch-theme.js b/site/themes/sine/static/js/switch-theme.js
new file mode 100644
index 0000000..5052f39
--- /dev/null
+++ b/site/themes/sine/static/js/switch-theme.js
@@ -0,0 +1,88 @@
+// const root = document.documentElement; // <html>, not <body>
+// const btn = document.getElementById("toggleTheme");
+//
+// const savedTheme = localStorage.getItem("theme") || "light";
+// root.className = savedTheme;
+// btn.innerHTML = savedTheme === "dark" ? "✧" : "☾";
+//
+// btn.addEventListener("click", () => {
+//   const newTheme = root.classList.contains("light") ? "dark" : "light";
+//   root.className = newTheme;
+//   localStorage.setItem("theme", newTheme);
+//   btn.innerHTML = newTheme === "dark" ? "✧" : "☾";
+// });
+
+/**
+* Utility function to calculate the current theme setting.
+* Look for a local storage value.
+* Fall back to system setting.
+* Fall back to light mode.
+*/
+function calculateSettingAsThemeString({ localStorageTheme, systemSettingDark }) {
+  if (localStorageTheme !== null) {
+    return localStorageTheme;
+  }
+
+  if (systemSettingDark.matches) {
+    return "dark";
+  }
+
+  return "light";
+}
+
+/**
+* Utility function to update the button text and aria-label.
+*/
+function updateButton({ buttonEl, isDark }) {
+  const newCta = isDark ? "Change to light theme" : "Change to dark theme";
+
+  const newInnerText = isDark ? "✧" : "☾";
+  // use an aria-label if you are omitting text on the button
+  // and using a sun/moon icon, for example
+  buttonEl.setAttribute("aria-label", newCta);
+  buttonEl.innerText = newInnerText;
+}
+
+/**
+* Utility function to update the theme setting on the html tag
+*/
+function updateThemeOnHtmlEl({ theme }) {
+  document.querySelector("html").setAttribute("data-theme", theme);
+}
+
+
+/**
+* On page load:
+*/
+
+/**
+* 1. Grab what we need from the DOM and system settings on page load
+*/
+const button = document.querySelector("[data-theme-toggle]");
+const localStorageTheme = localStorage.getItem("theme");
+const systemSettingDark = window.matchMedia("(prefers-color-scheme: dark)");
+
+/**
+* 2. Work out the current site settings
+*/
+let currentThemeSetting = calculateSettingAsThemeString({ localStorageTheme, systemSettingDark });
+
+/**
+* 3. Update the theme setting and button text accoridng to current settings
+*/
+updateButton({ buttonEl: button, isDark: currentThemeSetting === "dark" });
+updateThemeOnHtmlEl({ theme: currentThemeSetting });
+
+/**
+* 4. Add an event listener to toggle the theme
+*/
+button.addEventListener("click", (event) => {
+  const newTheme = currentThemeSetting === "dark" ? "light" : "dark";
+
+  localStorage.setItem("theme", newTheme);
+  updateButton({ buttonEl: button, isDark: newTheme === "dark" });
+  updateThemeOnHtmlEl({ theme: newTheme });
+
+  currentThemeSetting = newTheme;
+}); 
+