theme: set proper conditions

for having default-theme with theme-toggle

* can set/unset default theme
* for default-theme: dark/light : theme-toggle will not be visible
* theme-toggle with defaultheme: auto is functional

fixes #25 for #15

layouts/partials/footer.html

@@ -49,7 +49,7 @@
         localStorage.setItem("menu-scroll-position", document.getElementById('menu').scrollLeft);
     }
 </script>
-{{- if not .Site.Params.disableThemeToggle }}
+{{- if (and (not .Site.Params.disableThemeToggle) (not (or (eq .Site.Params.defaultTheme "light") (eq .Site.Params.defaultTheme "dark")))) }}
 <script>
     document.getElementById("theme-toggle").addEventListener("click", () => {
         if (document.body.className.includes("dark")) {
@@ -66,4 +66,4 @@
 <script>
     localStorage.removeItem("pref-theme");
 </script>
-{{- end }}
+{{- end }}

layouts/partials/header.html

@@ -1,4 +1,4 @@
-{{- if eq .Site.Params.defaultTheme "auto" }}
+{{- if (and (not .Site.Params.disableThemeToggle) (not (or (eq .Site.Params.defaultTheme "light") (eq .Site.Params.defaultTheme "dark")))) }}
 <script>
     // load memory
     if (localStorage.getItem("pref-theme") === "dark") {
@@ -12,6 +12,13 @@
     }
 </script>
 {{- end }}
+{{- if (and (.Site.Params.disableThemeToggle) (eq .Site.Params.defaultTheme "auto")) }}
+<script>
+    if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+        document.body.classList.add('dark');
+    }
+</script>
+{{- end }}
 <noscript>
     <style type="text/css">
         .theme-toggle,
@@ -24,7 +31,7 @@
     <nav class="nav">
         <p class="logo">
             <a href="{{ "" | absLangURL }}">{{ .Site.Title }}</a>
-            {{- if not .Site.Params.disableThemeToggle }}
+            {{- if (and (not .Site.Params.disableThemeToggle) (not (or (eq .Site.Params.defaultTheme "light") (eq .Site.Params.defaultTheme "dark")))) }}
             <span class="theme-toggle">
                 <a id="theme-toggle">
                     <svg id="moon" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24"