import { createSignal } from "solid-js";

// Persistence layer for collapsible (Zippy) panels. The cookie is a
// best-effort hint: the page always renders all Zippies closed unless
// their stable id is in the cookie's open-set, but a missing or
// corrupt cookie just falls back to "everything closed", so losing it
// (browser data clear, expiry, private window, write failure) is a
// pure cosmetic regression.
//
// localStorage would arguably be a tidier home for this — it's
// client-only and doesn't ride on every HTTP request — but the
// payload is tiny and the user asked for a cookie, so a cookie it
// is. SameSite=Lax keeps it from leaking to third-party iframes.

const COOKIE_NAME = "maglev_zippy_open";
const COOKIE_MAX_AGE = 60 * 60 * 24 * 365; // 1 year

function readCookie(): Set<string> {
  try {
    const raw = document.cookie.split("; ").find((c) => c.startsWith(COOKIE_NAME + "="));
    if (!raw) return new Set();
    const value = decodeURIComponent(raw.slice(COOKIE_NAME.length + 1));
    if (!value) return new Set();
    return new Set(value.split(","));
  } catch {
    return new Set();
  }
}

function writeCookie(ids: Set<string>) {
  try {
    const value = encodeURIComponent([...ids].join(","));
    document.cookie = `${COOKIE_NAME}=${value}; Path=/; Max-Age=${COOKIE_MAX_AGE}; SameSite=Lax`;
  } catch {
    // best-effort — quota, third-party-cookie blocks, etc. all silently fall back
  }
}

const [openSet, setOpenSet] = createSignal<Set<string>>(readCookie());

export function isZippyOpen(id: string): boolean {
  return openSet().has(id);
}

export function setZippyOpen(id: string, open: boolean) {
  const cur = openSet();
  if (open === cur.has(id)) return;
  const next = new Set(cur);
  if (open) next.add(id);
  else next.delete(id);
  setOpenSet(next);
  writeCookie(next);
}