import { writable } from 'svelte/store';
import { browser } from '$app/environment';

const TOKEN_KEY = 'eventsnap_jwt';
const PIN_KEY = 'eventsnap_pin';
const USER_ID_KEY = 'eventsnap_user_id';
const DISPLAY_NAME_KEY = 'eventsnap_display_name';

export const isAuthenticated = writable(false);

/**
 * Reactive mirror of `localStorage[PIN_KEY]`. Subscribers (the My Account page) see
 * the PIN change immediately when an SSE `pin-reset` event invalidates it from any
 * route — keeps the displayed PIN consistent with the server hash.
 */
export const currentPin = writable<string | null>(null);

export function getToken(): string | null {
	if (!browser) return null;
	return localStorage.getItem(TOKEN_KEY);
}

export function getPin(): string | null {
	if (!browser) return null;
	return localStorage.getItem(PIN_KEY);
}

/**
 * Clear the locally-cached recovery PIN. Called when the server resets it (host
 * action) — the cached plaintext no longer matches the bcrypt hash, so showing it
 * would mislead the user.
 */
export function clearPin(): void {
	if (!browser) return;
	localStorage.removeItem(PIN_KEY);
	currentPin.set(null);
}

export function getUserId(): string | null {
	if (!browser) return null;
	return localStorage.getItem(USER_ID_KEY);
}

export function getDisplayName(): string | null {
	if (!browser) return null;
	return localStorage.getItem(DISPLAY_NAME_KEY);
}

export function getExpiry(): Date | null {
	const token = getToken();
	if (!token) return null;
	try {
		const payload = JSON.parse(atob(token.split('.')[1]));
		return payload.exp ? new Date(payload.exp * 1000) : null;
	} catch {
		return null;
	}
}

export function setAuth(jwt: string, pin: string | null, userId: string, displayName?: string): void {
	if (!browser) return;
	localStorage.setItem(TOKEN_KEY, jwt);
	if (pin) {
		localStorage.setItem(PIN_KEY, pin);
		currentPin.set(pin);
	}
	localStorage.setItem(USER_ID_KEY, userId);
	if (displayName) localStorage.setItem(DISPLAY_NAME_KEY, displayName);
	isAuthenticated.set(true);
}

// Hook registry: cross-cutting stores (export-status, etc.) register a callback
// here at import-time so they get reset on every clearAuth path — both the
// explicit "Event verlassen" button and the api.ts 401 auto-clear. Keeps
// clearAuth the single source of truth without baking dependencies on every
// downstream store into this module (which would create circular imports).
const clearAuthHooks: Array<() => void> = [];
export function onClearAuth(fn: () => void): void {
	clearAuthHooks.push(fn);
}

export function clearAuth(): void {
	if (!browser) return;
	localStorage.removeItem(TOKEN_KEY);
	localStorage.removeItem(USER_ID_KEY);
	// PIN is intentionally kept so the user can recover
	isAuthenticated.set(false);
	// Hooks fire in registration order. Keep them dependency-free of each other —
	// if you ever need ordering, introduce a priority field rather than relying
	// on import-load timing, which is fragile across refactors.
	for (const fn of clearAuthHooks) {
		try { fn(); } catch { /* hook failure is non-fatal */ }
	}
}

export function getRole(): 'guest' | 'host' | 'admin' | null {
	const token = getToken();
	if (!token) return null;
	try {
		const payload = JSON.parse(atob(token.split('.')[1]));
		return payload.role ?? null;
	} catch {
		return null;
	}
}

export function initAuth(): void {
	if (!browser) return;
	isAuthenticated.set(!!getToken());
	currentPin.set(getPin());
}