tutu/src/serviceworker/workerrpc.ts

export type JSONRPC = {
  jsonrpc: "2.0";
  id?: string | number;
};

export type Call<T = undefined> = JSONRPC & {
  method: string;
  params: T;
};

export type RemoteError<E = undefined> = { data: E } & (
  | {
      code: number;
      message: string;
    }
  | {
      code: -32700;
      message: "Parse Error";
    }
  | {
      code: -32600;
      message: "Invalid Request";
    }
  | {
      code: -32601;
      message: "Method not found";
    }
  | {
      code: -32602;
      message: "Invalid params";
    }
  | {
      code: -32603;
      message: "Internal error";
    }
);

export type Result<T, E> = JSONRPC & { id: string | number } & (
    | {
        result: T;
        error: undefined;
      }
    | { error: RemoteError<E>; result: undefined }
  );

export function isJSONRPCResult(
  object: Record<string, unknown>,
): object is Result<unknown, unknown> {
  return object["jsonrpc"] === "2.0" && object["id"] && !object["method"];
}

export function isJSONRPCCall(
  object: Record<string, unknown>,
): object is Call<unknown> {
  return object["jsonrpc"] === "2.0" && !!object["method"];
}

export class ResultDispatcher {
  private map: Map<
    number | string,
    ((value: Result<unknown, unknown>) => void) | true // `true` = a call is generated, but the promise not created
  >;
  private nextId: number = Number.MIN_SAFE_INTEGER;

  constructor() {
    this.map = new Map();
  }

  private rollId() {
    let id = 0;
    while (this.map.get((id = this.nextId++))) {
      if (this.nextId >= Number.MAX_SAFE_INTEGER) {
        this.nextId = Number.MIN_SAFE_INTEGER;
      }
    }
    return id;
  }

  createCall<T>(
    method: string,
    params: T,
  ): [Promise<Call<T>>, Promise<Result<unknown, unknown>>] {
    const id = this.rollId();
    const p = new Promise<Result<unknown, unknown>>((resolve) =>
      this.map.set(id, resolve),
    );
    this.map.set(id, true);
    const call: Call<T> = {
      jsonrpc: "2.0",
      id,
      method,
      params,
    };

    return [
      new Promise((resolve) => {
        const waitUntilTheIdSet = () => {
          // We must do this check to make sure the id is set before the call made.
          // or the dispatching may lost the callback
          if (this.map.get(id)) {
            resolve(call);
          } else {
            setTimeout(waitUntilTheIdSet, 0);
          }
        };

        waitUntilTheIdSet();
      }),
      p,
    ];
  }

  dispatch(id: string | number, message: Result<unknown, unknown>) {
    {
      const callback = this.map.get(id);
      if (!callback) return;
      if (typeof callback !== "boolean") {
        callback(message);
        this.map.delete(id);
        return Promise.resolve();
      }
    }

    return new Promise<void>((resolve) => {
      let retried = 0;

      const checkAndDispatch = () => {
        const callback = this.map.get(id);
        if (typeof callback !== "boolean") {
          callback(message);
          this.map.delete(id);
          resolve();
          return;
        }
        setTimeout(checkAndDispatch, 0);
        if (++retried > 3) {
          console.warn(
            `retried ${retried} time(s) but the callback is still disappeared, id is "${id}"`,
          );
        }
      };

      // start the loop
      checkAndDispatch();
    });
  }

  createTypedCall<
    S extends AnyService,
    E = unknown,
    K extends keyof S = keyof S,
    P extends Parameters<S[K]> = Parameters<S[K]>,
    R extends ReturnType<S[K]> = ReturnType<S[K]>,
  >(method: K, ...params: P): [Promise<Call<P>>, Promise<Result<R, E>>] {
    return this.createCall(method as string, params) as [
      Promise<Call<P>>,
      Promise<Result<R, E>>,
    ];
  }
}

type AnyService = Record<string, ((...args: unknown[]) => unknown) | undefined>

export async function dispatchCall<
  S extends AnyService,
>(service: S, event: MessageEvent<Call<unknown>>) {
  try {
    const fn = service[event.data.method];
    if (!fn) {
      if (event.data.id)
        return event.source.postMessage({
          jsonrpc: "2.0",
          id: event.data.id,
          error: {
            code: -30601,
            message: "Method not found",
          },
        } as Result<void, void>);
    }

    try {
      const result = await fn(...event.data.params as unknown[]);

      if (!event.data.id) return;

      event.source.postMessage({
        jsonrpc: "2.0",
        id: event.data.id,
        result: result,
      } as Result<unknown, void>);
    } catch (reason) {
      event.source.postMessage({
        jsonrpc: "2.0",
        id: event.data.id,
        error: {
          code: 0,
          message: String(reason),
          data: reason,
        },
      } as Result<unknown, unknown>);
    }
  } catch (reason) {
    if (event.data.id)
      event.source.postMessage({
        jsonrpc: "2.0",
        id: event.data.id,
        error: {
          code: -32603,
          message: "Internal error",
          data: reason,
        },
      } as Result<void, unknown>);
  }
}