// 관심종목 — localStorage 기반. 로그인 없이 토스의 '내 종목' 느낌.
// 단순 string[] 직렬화. 다중 탭 동기화는 'storage' 이벤트로 처리.

const KEY = "stockchart.watchlist";

function read(): string[] {
  if (typeof window === "undefined") return [];
  try {
    const raw = window.localStorage.getItem(KEY);
    if (!raw) return [];
    const v = JSON.parse(raw);
    return Array.isArray(v) ? v.filter((s) => typeof s === "string") : [];
  } catch {
    return [];
  }
}

function write(codes: string[]) {
  if (typeof window === "undefined") return;
  window.localStorage.setItem(KEY, JSON.stringify(codes));
  // 같은 탭은 storage 이벤트가 안 떠서 수동 dispatch.
  window.dispatchEvent(new CustomEvent("watchlist:change"));
}

export const watchlist = {
  get(): string[] {
    return read();
  },
  has(code: string): boolean {
    return read().includes(code);
  },
  add(code: string): void {
    const cur = read();
    if (cur.includes(code)) return;
    write([code, ...cur]);
  },
  remove(code: string): void {
    const cur = read();
    write(cur.filter((c) => c !== code));
  },
  toggle(code: string): boolean {
    const cur = read();
    if (cur.includes(code)) {
      write(cur.filter((c) => c !== code));
      return false;
    }
    write([code, ...cur]);
    return true;
  },
  // 컴포넌트가 변경 구독. unsubscribe 함수 반환.
  subscribe(cb: () => void): () => void {
    if (typeof window === "undefined") return () => {};
    const onStorage = (e: StorageEvent) => {
      if (e.key === KEY) cb();
    };
    const onCustom = () => cb();
    window.addEventListener("storage", onStorage);
    window.addEventListener("watchlist:change", onCustom as EventListener);
    return () => {
      window.removeEventListener("storage", onStorage);
      window.removeEventListener("watchlist:change", onCustom as EventListener);
    };
  },
};