Initial commit for dark theme.

static/js/darkmode.js

@@ -0,0 +1,53 @@
+function enableDarkTheme() {
+  localStorage.setItem('color-scheme', "dark");
+  DarkReader.enable({
+      brightness: 100,
+      contrast: 90,
+      sepia: 10
+  });
+}
+
+function enableLightTheme() {
+  localStorage.setItem('color-scheme', "light");
+  DarkReader.disable();
+}
+
+function useSystemTheme() {
+  localStorage.setItem('color-scheme', "system");
+  if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
+    enableDarkTheme();
+  } else {
+    enableLightTheme();
+  }
+  window.matchMedia('(prefers-color-scheme: dark)').addEventListener('change', e => {
+    if (e.matches) {
+      enableDarkTheme();
+    } else {
+      enableLightTheme();
+    }
+  });
+}
+
+// Initialize. Use dark as default.
+function initializeColorScheme() {
+  // We're using the themeSelector attributes as a workaround for setting up
+  // the default coor scheme since we don't want to complicate this further by
+  // creating custom javascript output in Hugo.
+  themeSelector = document.getElementById("themeSelector");
+  defaultColorScheme = themeSelector.getAttribute('default-theme');
+  // If the user has already selected a preferred theme then use that instead
+  // of the default theme. Also, the default theme gets loaded to localStorage
+  // on the first visit.
+  if (!localStorage.getItem('color-scheme'))
+    localStorage.setItem('color-scheme', defaultColorScheme);
+  storedColorScheme = localStorage.getItem('color-scheme');
+  if (storedColorScheme == "light") {
+    enableLightTheme();
+  } else if (storedColorScheme == "system") {
+    useSystemTheme();
+  } else {
+    // Use dark theme as fallback since it is my default.
+    enableDarkTheme();
+  }
+}
+initializeColorScheme()