hnefatafl/src/lib/prefs.svelte.ts

// 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 }
];

/** Every table option is also a preference: the choice a new table starts with. The hall reads and writes the same keys. */
const TABLE_DEFAULTS: Preference[] = (game.options ?? []).map((o) => ({
	key: `table.${o.key}`,
	label: `${o.label}, for a new table`,
	kind: 'choice',
	choices: o.choices.map((c) => ({ value: c.value, label: c.label })),
	default: o.default
}));

export const PREFERENCES: Preference[] = [...KIT_PREFERENCES, ...TABLE_DEFAULTS, ...(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;
		}
	} 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;
}