From 52758459a220fde27f1519d3fd3e99f3f2a52f80 Mon Sep 17 00:00:00 2001
From: eltrac <hi@eltr.ac>
Date: Tue, 10 Feb 2026 15:39:50 +0800
Subject: feat: add theme switch

---
 assets/js/darkmode.js                          | 36 ++++++++++++++++++++++++++
 layouts/_partials/head.html                    |  3 ++-
 layouts/_partials/head/scripts.html            |  4 +++
 layouts/_partials/header/other-navigation.html |  7 +++++
 4 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 assets/js/darkmode.js
 create mode 100644 layouts/_partials/head/scripts.html

diff --git a/assets/js/darkmode.js b/assets/js/darkmode.js
new file mode 100644
index 00000000..6057f357
--- /dev/null
+++ b/assets/js/darkmode.js
@@ -0,0 +1,36 @@
+(() => {
+    const THEME = 'geedeapro.theme' // auto | light | dakr
+    const mql = window.matchMedia('(prefers-color-scheme: dark)')
+
+    function useDarkMode(store) {
+        document.documentElement.classList.add('dark')
+        if (localStorage.getItem(THEME) != 'auto') mql.onchange = null
+        if (store) localStorage.setItem(THEME, 'dark')
+    }
+
+    function useLightMode(store) {
+        document.documentElement.classList.remove('dark')
+        if (localStorage.getItem(THEME) != 'auto') mql.onchange = null
+        if (store) localStorage.setItem(THEME, 'light')
+    }
+
+    function useSystem(store) {
+        if (mql.matches) useDarkMode()
+        else useLightMode()
+        mql.onchange = e => {
+            console.log("changed when system changed")
+            if (e.matches) useDarkMode()
+            else useLightMode()
+        }
+        if (store) localStorage.setItem(THEME, 'auto')
+    }
+
+    window.switchTheme = (theme, store) => {
+        if (!theme || theme === 'auto') useSystem(store)
+        else if (theme === 'dark') useDarkMode(store)
+        else if (theme === 'light') useLightMode(store)
+    }
+
+    // use preferred theme immediately upon DOM loaded
+    window.switchTheme(localStorage.getItem(THEME), false)
+})();
diff --git a/layouts/_partials/head.html b/layouts/_partials/head.html
index a50dd333..3a8cd25c 100644
--- a/layouts/_partials/head.html
+++ b/layouts/_partials/head.html
@@ -4,6 +4,7 @@
   <link rel="preconnect" href="https://r2.eltr.ac" />
   {{ hugo.Generator }}
   {{ partial "head/siteinfo" . }}
-  {{ partial "head/css" . }}
   {{ partial "head/verification" . }}
+  {{ partial "head/css" . }}
+  {{ partial "head/scripts" . }}
 </head>
diff --git a/layouts/_partials/head/scripts.html b/layouts/_partials/head/scripts.html
new file mode 100644
index 00000000..f067944c
--- /dev/null
+++ b/layouts/_partials/head/scripts.html
@@ -0,0 +1,4 @@
+{{ with resources.Get "js/darkmode.js" }}
+<script>{{ .Content | safeJS }}</script>
+{{ end }}
+
diff --git a/layouts/_partials/header/other-navigation.html b/layouts/_partials/header/other-navigation.html
index 662f1076..ab6035f1 100644
--- a/layouts/_partials/header/other-navigation.html
+++ b/layouts/_partials/header/other-navigation.html
@@ -1,6 +1,13 @@
 {{ $langButtonSize := "w-4 h-4" }}
 
 <div class="flex gap-2 pr-2">
+    <!-- theme switch -->
+    <select onchange="switchTheme(this.value, true)" id="theme-select">
+    {{ $switches := slice "auto" "light" "dark" }}
+    {{ range $switches }}
+        <option>{{ . }}</option>
+    {{ end }}
+    </select>
     <!-- language switch -->
     {{- $lang := .Site.Language.Lang -}}
     {{- $switch := dict
-- 
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