Add ThemeProvider

CONTEXT.md

@@ -75,6 +75,23 @@ The project uses shadcn/ui components located in `@/components/ui`. These are un
 
 These components follow a consistent pattern using React's `forwardRef` and use the `cn()` utility for class name merging. Many are built on Radix UI primitives for accessibility and customized with Tailwind CSS.
 
+## Theme Toggle Component
+
+A pre-built theme toggle component is available for easy integration:
+
+```tsx
+import { ThemeToggle } from "@/components/theme-toggle";
+
+function Header() {
+  return (
+    <header>
+      <h1>My App</h1>
+      <ThemeToggle />
+    </header>
+  );
+}
+```
+
 ## Nostr Protocol Integration
 
 This project comes with custom hooks for querying and publishing events on the Nostr network.

src/App.tsx

@@ -2,6 +2,7 @@
 // To add new routes, edit the AppRouter.tsx file.
 
 import NostrProvider from '@/components/NostrProvider'
+import { ThemeProvider } from "@/components/ThemeProvider";
 import { Toaster } from "@/components/ui/toaster";
 import { Toaster as Sonner } from "@/components/ui/sonner";
 import { TooltipProvider } from "@/components/ui/tooltip";
@@ -28,6 +29,7 @@ const queryClient = new QueryClient({
 
 export function App() {
   return (
+    <ThemeProvider defaultTheme="system">
       <NostrLoginProvider storageKey='nostr:login'>
         <NostrProvider relays={defaultRelays}>
           <QueryClientProvider client={queryClient}>
@@ -39,6 +41,7 @@ export function App() {
           </QueryClientProvider>
         </NostrProvider>
       </NostrLoginProvider>
+    </ThemeProvider>
   );
 }
 

src/components/ThemeProvider.tsx

@@ -0,0 +1,69 @@
+import { useEffect, useState } from "react"
+import { Theme, ThemeProviderContext } from "@/lib/theme-context"
+
+type ThemeProviderProps = {
+  children: React.ReactNode
+  defaultTheme?: Theme
+  storageKey?: string
+}
+
+export function ThemeProvider({
+  children,
+  defaultTheme = "system",
+  storageKey = "theme",
+  ...props
+}: ThemeProviderProps) {
+  const [theme, setTheme] = useState<Theme>(
+    () => (localStorage.getItem(storageKey) as Theme) || defaultTheme
+  )
+
+  useEffect(() => {
+    const root = window.document.documentElement
+
+    root.classList.remove("light", "dark")
+
+    if (theme === "system") {
+      const systemTheme = window.matchMedia("(prefers-color-scheme: dark)")
+        .matches
+        ? "dark"
+        : "light"
+
+      root.classList.add(systemTheme)
+      return
+    }
+
+    root.classList.add(theme)
+  }, [theme])
+
+  useEffect(() => {
+    const mediaQuery = window.matchMedia("(prefers-color-scheme: dark)")
+    
+    const handleChange = () => {
+      if (theme === "system") {
+        const root = window.document.documentElement
+        root.classList.remove("light", "dark")
+        
+        const systemTheme = mediaQuery.matches ? "dark" : "light"
+        root.classList.add(systemTheme)
+      }
+    }
+
+    mediaQuery.addEventListener("change", handleChange)
+    return () => mediaQuery.removeEventListener("change", handleChange)
+  }, [theme])
+
+  const value = {
+    theme,
+    setTheme: (theme: Theme) => {
+      localStorage.setItem(storageKey, theme)
+      setTheme(theme)
+    },
+  }
+
+  return (
+    <ThemeProviderContext.Provider {...props} value={value}>
+      {children}
+    </ThemeProviderContext.Provider>
+  )
+}
+

src/components/ThemeToggle.tsx

@@ -0,0 +1,37 @@
+import { Moon, Sun } from "lucide-react"
+
+import { Button } from "@/components/ui/button"
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from "@/components/ui/dropdown-menu"
+import { useTheme } from "@/hooks/useTheme"
+
+export function ThemeToggle() {
+  const { setTheme } = useTheme()
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button variant="outline" size="icon">
+          <Sun className="h-[1.2rem] w-[1.2rem] rotate-0 scale-100 transition-all dark:-rotate-90 dark:scale-0" />
+          <Moon className="absolute h-[1.2rem] w-[1.2rem] rotate-90 scale-0 transition-all dark:rotate-0 dark:scale-100" />
+          <span className="sr-only">Toggle theme</span>
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end">
+        <DropdownMenuItem onClick={() => setTheme("light")}>
+          Light
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme("dark")}>
+          Dark
+        </DropdownMenuItem>
+        <DropdownMenuItem onClick={() => setTheme("system")}>
+          System
+        </DropdownMenuItem>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  )
+}

src/hooks/useTheme.ts

@@ -0,0 +1,11 @@
+import { useContext } from "react"
+import { ThemeProviderContext } from "@/lib/theme-context"
+
+export const useTheme = () => {
+  const context = useContext(ThemeProviderContext)
+
+  if (context === undefined)
+    throw new Error("useTheme must be used within a ThemeProvider")
+
+  return context
+}

src/lib/theme-context.ts

@@ -0,0 +1,15 @@
+import { createContext } from "react";
+
+export type Theme = "dark" | "light" | "system";
+
+export type ThemeProviderState = {
+  theme: Theme;
+  setTheme: (theme: Theme) => void;
+};
+
+const initialState: ThemeProviderState = {
+  theme: "system",
+  setTheme: () => null,
+};
+
+export const ThemeProviderContext = createContext<ThemeProviderState>(initialState);