Add wallpaper picker and compression script

src/lib/theme/wallpaper.svelte.ts

@@ -0,0 +1,52 @@
+import { wallpapers, type Wallpaper } from '#lib/content';
+
+const wallpaperStorageKey = 'wallpaper';
+
+function readStoredWallpaperId(): string | null {
+	try {
+		return localStorage.getItem(wallpaperStorageKey);
+	} catch {
+		return null;
+	}
+}
+
+function storeWallpaperId(wallpaperId: string | null) {
+	try {
+		if (wallpaperId) localStorage.setItem(wallpaperStorageKey, wallpaperId);
+		else localStorage.removeItem(wallpaperStorageKey);
+	} catch {}
+}
+
+function findWallpaper(wallpaperId: string | null): Wallpaper | null {
+	return wallpapers.find((wallpaper) => wallpaper.id === wallpaperId) ?? null;
+}
+
+function applyWallpaper(wallpaper: Wallpaper | null) {
+	const rootStyle = document.documentElement.style;
+	if (wallpaper) rootStyle.setProperty('--wallpaper', `url('${wallpaper.image}')`);
+	else rootStyle.removeProperty('--wallpaper');
+}
+
+class WallpaperState {
+	currentId = $state<string | null>(null);
+
+	restore() {
+		const stored = findWallpaper(readStoredWallpaperId());
+		this.currentId = stored?.id ?? null;
+		applyWallpaper(stored);
+	}
+
+	set(wallpaperId: string | null) {
+		const wallpaper = findWallpaper(wallpaperId);
+		this.currentId = wallpaper?.id ?? null;
+		applyWallpaper(wallpaper);
+		storeWallpaperId(this.currentId);
+	}
+
+	shuffle() {
+		const choices = wallpapers.filter((wallpaper) => wallpaper.id !== this.currentId);
+		if (choices.length) this.set(choices[Math.floor(Math.random() * choices.length)].id);
+	}
+}
+
+export const wallpaperState = new WallpaperState();