super-simple-rpc.ts

interface RpcModules {
  "example-remote-module": MapReturnTypesToPromise<
    typeof import("example-remote-module")
  >;
}

export function importRemote<S extends keyof RpcModules>(
  module: S
): RpcModules[S] {
  return new Proxy({} as any, {
    get(_t, func) {
      return async (...args: unknown[]) => {
        return fetch("/api/rpc", {
          method: "POST",
          // TODO: Use a more powerful serializer
          body: JSON.stringify({ module, func, args }),
          headers: { "content-type": "application/json" },
        })
          .then((r) => r.json())
          .then((j) => {
            if (j.error) {
              // TODO: Standardize error format
              throw j.error.message;
            }
            return j.result;
          });
      };
    },
  });
}

type MapReturnTypesToPromise<T extends Record<string, any>> = {
  [k in keyof T]: MapReturnTypeToPromise<T[k]>;
};

type Promisify<T> = T extends Promise<any> ? T : Promise<T>;

type MapReturnTypeToPromise<T> = T extends (
  ctx: any,
  ...args: infer A
) => infer R
  ? (...args: A) => Promisify<R>
  : never;