claude-code

web/lib/theme.tsx

@@ -0,0 +1,74 @@
+'use client'
+
+import React, { createContext, useContext, useEffect, useState } from 'react'
+
+export type Theme = 'dark' | 'light' | 'system'
+export type ResolvedTheme = 'dark' | 'light'
+
+interface ThemeContextValue {
+  theme: Theme
+  resolvedTheme: ResolvedTheme
+  setTheme: (theme: Theme) => void
+}
+
+const ThemeContext = createContext<ThemeContextValue | null>(null)
+
+export function ThemeProvider({
+  children,
+  defaultTheme = 'dark',
+  storageKey = 'ui-theme',
+}: {
+  children: React.ReactNode
+  defaultTheme?: Theme
+  storageKey?: string
+}) {
+  const [theme, setThemeState] = useState<Theme>(defaultTheme)
+  const [resolvedTheme, setResolvedTheme] = useState<ResolvedTheme>('dark')
+
+  useEffect(() => {
+    const stored = localStorage.getItem(storageKey) as Theme | null
+    if (stored && ['dark', 'light', 'system'].includes(stored)) {
+      setThemeState(stored)
+    }
+  }, [storageKey])
+
+  useEffect(() => {
+    const root = document.documentElement
+
+    const apply = (resolved: ResolvedTheme) => {
+      setResolvedTheme(resolved)
+      if (resolved === 'light') {
+        root.classList.add('light')
+      } else {
+        root.classList.remove('light')
+      }
+    }
+
+    if (theme === 'system') {
+      const mq = window.matchMedia('(prefers-color-scheme: light)')
+      apply(mq.matches ? 'light' : 'dark')
+      const handler = (e: MediaQueryListEvent) => apply(e.matches ? 'light' : 'dark')
+      mq.addEventListener('change', handler)
+      return () => mq.removeEventListener('change', handler)
+    } else {
+      apply(theme)
+    }
+  }, [theme])
+
+  const setTheme = (t: Theme) => {
+    setThemeState(t)
+    localStorage.setItem(storageKey, t)
+  }
+
+  return (
+    <ThemeContext.Provider value={{ theme, resolvedTheme, setTheme }}>
+      {children}
+    </ThemeContext.Provider>
+  )
+}
+
+export function useTheme(): ThemeContextValue {
+  const ctx = useContext(ThemeContext)
+  if (!ctx) throw new Error('useTheme must be used within a ThemeProvider')
+  return ctx
+}