// A claim made on one Referrals page tells this browser's other open pages, so a queue left open in another tab
// looks for the claimed referral instead of showing the old list until a reload. The hint names the practice and
// the referral id only: nothing about the patient or the reason, and it grants nothing. A page that hears it
// reads its own queue with its own authority, and only for the practice it is showing.

const CHANNEL = "akashic-referral-claims";

export type ReferralClaimHint = { kind: "claimed" | "matched"; practice: string; referralId: string };

const asHint = (data: unknown): ReferralClaimHint | undefined => {
  const hint = data as Partial<ReferralClaimHint> | null;
  if (!hint || (hint.kind !== "claimed" && hint.kind !== "matched")) return undefined;
  if (typeof hint.practice !== "string" || !hint.practice) return undefined;
  if (typeof hint.referralId !== "string" || !hint.referralId) return undefined;
  return { kind: hint.kind, practice: hint.practice, referralId: hint.referralId };
};

/** Listens for other pages' claims and posts this page's; a page never hears its own. Close it with the page. */
export const openReferralClaimHints = (onHint: (hint: ReferralClaimHint) => void) => {
  if (typeof BroadcastChannel === "undefined") return { post: () => undefined, close: () => undefined };
  const channel = new BroadcastChannel(CHANNEL);
  channel.onmessage = (event: MessageEvent) => {
    const hint = asHint(event.data);
    if (hint) onHint(hint);
  };
  return {
    post: (hint: ReferralClaimHint) => channel.postMessage(asHint(hint)),
    close: () => channel.close(),
  };
};