import { defineError, ensure, declares, tryAsync, match } from "@chan.run/ensure";

// Error catalog for the users domain
const UserNotFoundError = defineError("UserNotFoundError");
const DbError = defineError("DbError");

// Declare what getUser can throw — type flows through tryAsync
const getUser = declares([UserNotFoundError, DbError], async (id: string) => {
  const row = await db.users.findById(id);
  return ensure(row, UserNotFoundError, `No user: ${id}`);
});

export async function handleGetUser(req: Request): Promise<Response> {
  const result = await tryAsync(getUser, req.params.id);

  if (result.ok) {
    return Response.json(result.data);
  }

  // TypeScript enforces you handle both error types
  return match(result.error, [UserNotFoundError, DbError], {
    UserNotFoundError: (err) => Response.json({ error: err.message }, { status: 404 }),
    DbError: (err) => Response.json({ error: "Service unavailable" }, { status: 503 }),
  });
}