import {
  ok,
  err,
  UnauthenticatedError,
  type CallerContext,
  type ReadonlyDB,
} from "@tailor-platform/erp-kit/core";
import type { DB } from "../generated/kysely-tailordb";

export interface GetNotificationInput {
  id: string;
}

/**
 * Returns a Notification by id when the caller is its recipient; otherwise null (no existence oracle).
 */
export async function run(db: ReadonlyDB<DB>, input: GetNotificationInput, ctx: CallerContext) {
  // Every result here is scoped to the caller, so there is nothing to return when
  // there is no caller. Queries carry no permission gate of their own.
  const { actorId } = ctx;
  if (actorId === null) return err(new UnauthenticatedError());
  const notification = await db
    .selectFrom("Notification")
    .selectAll()
    .where("id", "=", input.id)
    .executeTakeFirst();

  if (!notification) {
    return ok({ notification: null });
  }

  // Self-scope: a notification owned by another user is reported exactly like
  // a missing one (null) so callers cannot enumerate foreign notification ids.
  if (notification.recipientUserId !== actorId) {
    return ok({ notification: null });
  }

  return ok({ notification });
}