feat: implement custom ThemeProvider without next-themes

Create React Context-based theme provider with localStorage support.

Co-authored-by: Simon <85533298+handsomezhuzhu@users.noreply.github.com>

components/theme-provider.tsx

@@ -1,12 +1,101 @@
 "use client"
 
-import type * as React from "react"
-import { ThemeProvider as NextThemesProvider } from "next-themes"
+import * as React from "react"
+import { createContext, useContext, useEffect, useState } from "react"
 
-export { useTheme } from "next-themes"
+type Theme = "dark" | "light" | "system"
 
-type ThemeProviderProps = React.ComponentProps<typeof NextThemesProvider>
-
-export function ThemeProvider({ children, ...props }: ThemeProviderProps) {
-  return <NextThemesProvider {...props}>{children}</NextThemesProvider>
+type ThemeProviderProps = {
+  children: React.ReactNode
+  defaultTheme?: Theme
+  storageKey?: string
+  attribute?: string
+  enableSystem?: boolean
+  disableTransitionOnChange?: boolean
+}
+
+type ThemeProviderState = {
+  theme: Theme
+  setTheme: (theme: Theme) => void
+  resolvedTheme?: string
+}
+
+const ThemeProviderContext = createContext<ThemeProviderState | undefined>(undefined)
+
+export function ThemeProvider({
+  children,
+  defaultTheme = "system",
+  storageKey = "theme",
+  ...props
+}: ThemeProviderProps) {
+  const [theme, setTheme] = useState<Theme>(defaultTheme)
+  const [resolvedTheme, setResolvedTheme] = useState<string | undefined>(undefined)
+  const [mounted, setMounted] = useState(false)
+
+  useEffect(() => {
+    setMounted(true)
+    const stored = localStorage.getItem(storageKey) as Theme | null
+    if (stored) {
+      setTheme(stored)
+    }
+  }, [storageKey])
+
+  useEffect(() => {
+    if (!mounted) return
+
+    const root = window.document.documentElement
+
+    root.classList.remove("light", "dark")
+
+    let resolved: string
+    if (theme === "system") {
+      resolved = window.matchMedia("(prefers-color-scheme: dark)").matches ? "dark" : "light"
+    } else {
+      resolved = theme
+    }
+
+    root.classList.add(resolved)
+    setResolvedTheme(resolved)
+  }, [theme, mounted])
+
+  useEffect(() => {
+    if (!mounted || theme !== "system") return
+
+    const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)")
+    const handleChange = () => {
+      const resolved = mediaQuery.matches ? "dark" : "light"
+      const root = window.document.documentElement
+      root.classList.remove("light", "dark")
+      root.classList.add(resolved)
+      setResolvedTheme(resolved)
+    }
+
+    mediaQuery.addEventListener("change", handleChange)
+    return () => mediaQuery.removeEventListener("change", handleChange)
+  }, [theme, mounted])
+
+  const value = {
+    theme,
+    setTheme: (newTheme: Theme) => {
+      localStorage.setItem(storageKey, newTheme)
+      setTheme(newTheme)
+    },
+    resolvedTheme,
+  }
+
+  return (
+    <ThemeProviderContext.Provider value={value}>
+      {children}
+    </ThemeProviderContext.Provider>
+  )
+}
+
+export function useTheme() {
+  const context = useContext(ThemeProviderContext)
+
+  if (context === undefined) {
+    throw new Error("useTheme must be used within a ThemeProvider")
+  }
+
+  return context
 }