chore: initialize project

src/components/ThemeToggle.tsx

@@ -0,0 +1,81 @@
+import { useEffect, useState } from 'react'
+
+type ThemeMode = 'light' | 'dark' | 'auto'
+
+function getInitialMode(): ThemeMode {
+  if (typeof window === 'undefined') {
+    return 'auto'
+  }
+
+  const stored = window.localStorage.getItem('theme')
+  if (stored === 'light' || stored === 'dark' || stored === 'auto') {
+    return stored
+  }
+
+  return 'auto'
+}
+
+function applyThemeMode(mode: ThemeMode) {
+  const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches
+  const resolved = mode === 'auto' ? (prefersDark ? 'dark' : 'light') : mode
+
+  document.documentElement.classList.remove('light', 'dark')
+  document.documentElement.classList.add(resolved)
+
+  if (mode === 'auto') {
+    document.documentElement.removeAttribute('data-theme')
+  } else {
+    document.documentElement.setAttribute('data-theme', mode)
+  }
+
+  document.documentElement.style.colorScheme = resolved
+}
+
+export default function ThemeToggle() {
+  const [mode, setMode] = useState<ThemeMode>('auto')
+
+  useEffect(() => {
+    const initialMode = getInitialMode()
+    setMode(initialMode)
+    applyThemeMode(initialMode)
+  }, [])
+
+  useEffect(() => {
+    if (mode !== 'auto') {
+      return
+    }
+
+    const media = window.matchMedia('(prefers-color-scheme: dark)')
+    const onChange = () => applyThemeMode('auto')
+
+    media.addEventListener('change', onChange)
+    return () => {
+      media.removeEventListener('change', onChange)
+    }
+  }, [mode])
+
+  function toggleMode() {
+    const nextMode: ThemeMode =
+      mode === 'light' ? 'dark' : mode === 'dark' ? 'auto' : 'light'
+    setMode(nextMode)
+    applyThemeMode(nextMode)
+    window.localStorage.setItem('theme', nextMode)
+  }
+
+  const label =
+    mode === 'auto'
+      ? 'Theme mode: auto (system). Click to switch to light mode.'
+      : `Theme mode: ${mode}. Click to switch mode.`
+
+  return (
+    <button
+      type="button"
+      onClick={toggleMode}
+      aria-label={label}
+      title={label}
+      className="rounded-full border border-[var(--chip-line)] bg-[var(--chip-bg)] px-3 py-1.5 text-sm font-semibold text-[var(--sea-ink)] shadow-[0_8px_22px_rgba(30,90,72,0.08)] transition hover:-translate-y-0.5"
+    >
+      {mode === 'auto' ? 'Auto' : mode === 'dark' ? 'Dark' : 'Light'}
+    </button>
+  )
+}