| 1 | import { useEffect, useState } from "react"; |
| 2 | |
| 3 | type ThemeMode = "light" | "dark" | "auto"; |
| 4 | |
| 5 | function getInitialMode(): ThemeMode { |
| 6 | if (typeof window === "undefined") { |
| 7 | return "auto"; |
| 8 | } |
| 9 | |
| 10 | const stored = window.localStorage.getItem("theme"); |
| 11 | if (stored === "light" || stored === "dark" || stored === "auto") { |
| 12 | return stored; |
| 13 | } |
| 14 | |
| 15 | return "auto"; |
| 16 | } |
| 17 | |
| 18 | function applyThemeMode(mode: ThemeMode) { |
| 19 | const prefersDark = window.matchMedia("(prefers-color-scheme: dark)").matches; |
| 20 | const resolved = mode === "auto" ? (prefersDark ? "dark" : "light") : mode; |
| 21 | |
| 22 | document.documentElement.classList.remove("light", "dark"); |
| 23 | document.documentElement.classList.add(resolved); |
| 24 | |
| 25 | if (mode === "auto") { |
| 26 | document.documentElement.removeAttribute("data-theme"); |
| 27 | } else { |
| 28 | document.documentElement.setAttribute("data-theme", mode); |
| 29 | } |
| 30 | |
| 31 | document.documentElement.style.colorScheme = resolved; |
| 32 | } |
| 33 | |
| 34 | export default function ThemeToggle() { |
| 35 | const [mode, setMode] = useState<ThemeMode>("auto"); |
| 36 | |
| 37 | useEffect(() => { |
| 38 | const initialMode = getInitialMode(); |
| 39 | setMode(initialMode); |
| 40 | applyThemeMode(initialMode); |
| 41 | }, []); |
| 42 | |
| 43 | useEffect(() => { |
| 44 | if (mode !== "auto") { |
| 45 | return; |
| 46 | } |
| 47 | |
| 48 | const media = window.matchMedia("(prefers-color-scheme: dark)"); |
| 49 | const onChange = () => applyThemeMode("auto"); |
| 50 | |
| 51 | media.addEventListener("change", onChange); |
| 52 | return () => { |
| 53 | media.removeEventListener("change", onChange); |
| 54 | }; |
| 55 | }, [mode]); |
| 56 | |
| 57 | function toggleMode() { |
| 58 | const nextMode: ThemeMode = |
| 59 | mode === "light" ? "dark" : mode === "dark" ? "auto" : "light"; |
| 60 | setMode(nextMode); |
| 61 | applyThemeMode(nextMode); |
| 62 | window.localStorage.setItem("theme", nextMode); |
| 63 | } |
| 64 | |
| 65 | const label = |
| 66 | mode === "auto" |
| 67 | ? "Theme mode: auto (system). Click to switch to light mode." |
| 68 | : `Theme mode: ${mode}. Click to switch mode.`; |
| 69 | |
| 70 | return ( |
| 71 | <button |
| 72 | type="button" |
| 73 | onClick={toggleMode} |
| 74 | aria-label={label} |
| 75 | title={label} |
| 76 | 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" |
| 77 | > |
| 78 | {mode === "auto" ? "Auto" : mode === "dark" ? "Dark" : "Light"} |
| 79 | </button> |
| 80 | ); |
| 81 | } |