Recover integration connections

import {
  createIntegrationClient,
  type IntegrationClientConnection,
  type IntegrationConnectionStatus,
} from "veryfront/integrations";

/**
 * Shows the one-time URL to the signed-in person, for example in your UI, and
 * resolves once it is shown, not after consent. Never log it.
 */
export type PresentConnectUrl = (url: string, expiresAt: string) => Promise<void>;

/** Settles with `work`, or rejects when the deadline fires first. */
function untilDeadline<T>(work: Promise<T>, deadline: AbortSignal): Promise<T> {
  return new Promise<T>((resolve, reject) => {
    const abort = () => reject(deadline.reason);
    if (deadline.aborted) {
      void work.catch(() => {}); // A late rejection from `work` has no one to report to.
      return abort();
    }
    deadline.addEventListener("abort", abort, { once: true });
    work.then(resolve, reject).finally(() => deadline.removeEventListener("abort", abort));
  });
}

function identity(status: IntegrationConnectionStatus): string | undefined {
  const id = status.connection_id ?? status.connectionId;
  const generation = status.connection_generation_id ?? status.connectionGenerationId;
  return status.connected && id && generation ? `${id}:${generation}` : undefined;
}

export async function connectGmail(
  presentConnectUrl: PresentConnectUrl,
): Promise<IntegrationClientConnection> {
  // One deadline bounds every request this client makes, including connect.
  const deadline = AbortSignal.timeout(5 * 60 * 1000);
  const client = await createIntegrationClient({
    apiBaseUrl: "<API_BASE_URL>",
    authToken: "<TOKEN>",
    projectReference: "<PROJECT_SLUG>",
    abortSignal: deadline,
  });
  const scope = "user";
  const before = identity(await client.status("gmail", scope));
  const handoff = await client.connect("gmail", { scope, redirectUri: "<REDIRECT_URI>" });
  if (handoff.status !== "oauth_handoff") throw new Error(`Gmail needs setup: ${handoff.status}`);
  // The one-time URL is useless after expires_at, so showing it must finish first.
  const showBy = AbortSignal.any([
    deadline,
    AbortSignal.timeout(Math.max(0, Date.parse(handoff.expires_at) - Date.now())),
  ]);
  await untilDeadline(presentConnectUrl(handoff.connect_url, handoff.expires_at), showBy);

  while (true) {
    await untilDeadline(new Promise((resolve) => setTimeout(resolve, 3000)), deadline);
    const current = identity(await client.status("gmail", scope));
    if (!current || current === before) continue;
    for await (const row of client.listConnections("gmail")) {
      const matches = `${row.id}:${row.connection_generation_id}` === current;
      if (matches && row.scope === scope && row.status === "connected") return row;
    }
  }
}