import { useState } from "react";

const STORAGE_KEY = "verse-quote-app.visitor-id";

function generateId(): string {
  if (typeof crypto !== "undefined" && "randomUUID" in crypto) {
    return crypto.randomUUID();
  }
  return `v-${Date.now()}-${Math.random().toString(36).slice(2, 10)}`;
}

/**
 * A stable anonymous id for this browser, used to scope favorites without
 * requiring a login. Not a real user identity — just enough to remember
 * "your" favorites on this device.
 */
export function getVisitorId(): string {
  if (typeof window === "undefined") return "";
  try {
    const existing = window.localStorage.getItem(STORAGE_KEY);
    if (existing) return existing;
    const created = generateId();
    window.localStorage.setItem(STORAGE_KEY, created);
    return created;
  } catch {
    return generateId();
  }
}

/**
 * React hook wrapper around getVisitorId(). Routes that use this render only
 * an SSR loading shell (see DEVELOPING.md), so reading localStorage during
 * the initial client render here does not cause a hydration mismatch.
 */
export function useVisitorId(): string {
  const [visitorId] = useState(() => getVisitorId());
  return visitorId;
}