Preferences: motion, confirming a move, coordinates on the board, and the last table choices remembered

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jm2auWk6RP71CjaAb4FMoG

src/lib/prefs.svelte.ts

@@ -0,0 +1,65 @@
+// Preferences: what this browser remembers about how its player likes to
+// play. The kit's own settings are motion and whether a move is confirmed
+// before it is sent; a game declares more in GameSpec.preferences, and the
+// panel renders every declaration. Nothing here leaves the browser.
+
+import { game } from '$lib/game';
+
+export interface Preference {
+	key: string;
+	label: string;
+	/** A toggle holds a boolean; a choice holds one of its choices' values. */
+	kind: 'toggle' | 'choice';
+	choices?: { value: string; label: string }[];
+	default: boolean | string;
+	note?: string;
+}
+
+/** The settings every game in the kit shares. */
+export const KIT_PREFERENCES: Preference[] = [
+	{ key: 'motion', label: 'Motion', kind: 'choice', choices: [{ value: 'full', label: 'pieces move and fade' }, { value: 'reduced', label: 'changes appear at once' }], default: 'full' },
+	{ key: 'confirmMoves', label: 'Confirm a move before it is sent', kind: 'toggle', default: false }
+];
+
+export const PREFERENCES: Preference[] = [...KIT_PREFERENCES, ...(game.preferences ?? [])];
+
+const KEY = 'hnefatafl:prefs';
+
+function defaults(): Record<string, boolean | string> {
+	return Object.fromEntries(PREFERENCES.map((p) => [p.key, p.default]));
+}
+
+function load(): Record<string, boolean | string> {
+	const base = defaults();
+	try {
+		const saved = JSON.parse(localStorage.getItem(KEY) ?? '{}') as Record<string, unknown>;
+		for (const p of PREFERENCES) {
+			const v = saved[p.key];
+			if (p.kind === 'toggle' && typeof v === 'boolean') base[p.key] = v;
+			if (p.kind === 'choice' && typeof v === 'string' && p.choices?.some((c) => c.value === v)) base[p.key] = v;
+		}
+		// The hall's last table options ride along under table.<key>, undeclared.
+		for (const [k, v] of Object.entries(saved)) if (k.startsWith('table.') && typeof v === 'string') base[k] = v;
+	} catch {
+		// Without storage the defaults apply for this visit.
+	}
+	return base;
+}
+
+/** The live preferences; read them where they matter, set them through setPref. */
+export const prefs = $state<Record<string, boolean | string>>(typeof localStorage === 'undefined' ? defaults() : load());
+
+export function setPref(key: string, value: boolean | string): void {
+	prefs[key] = value;
+	try {
+		localStorage.setItem(KEY, JSON.stringify(prefs));
+	} catch {
+		// The change still applies for this visit.
+	}
+}
+
+/** The reduced-motion preference, or the system's, whichever asks for calm. */
+export function reducedMotion(): boolean {
+	if (prefs.motion === 'reduced') return true;
+	return typeof matchMedia !== 'undefined' && matchMedia('(prefers-reduced-motion: reduce)').matches;
+}