@c9up/comet

Agnostic JSON-RPC 2.0 protocol + an isomorphic, transport-injectable client for the Ream framework. Zero framework, zero transport, zero dependency — the browser binding (@c9up/aurora) and the server binding (@c9up/ream's RpcRouter) both build on this core instead of hand-rolling the envelope and error codes.

Client

The client owns the JSON-RPC logic (single + batch, id matching, error mapping) and delegates the actual bytes to an injected transport — so the same client runs in the browser or in Node:

import { createRpcClient } from "@c9up/comet";

const rpc = createRpcClient({
  url: "/rpc",
  transport: (url, body, { signal }) =>
    fetch(url, {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify(body),
      signal,
    }).then((r) => r.json()),
});

const out = await rpc.call("task.validate", { id: 7 });          // typed via call<T>()
await rpc.call("user.find", { id }, { parse: isUser });          // runtime-validated
await rpc.call("slow.op", p, { signal: ac.signal });             // abortable
const results = await rpc.batch([{ method: "a" }, { method: "b" }]); // settled per call

In the browser, prefer @c9up/aurora's createRpcClient — it wires aurora's HttpClient (base URL, auth headers, timeouts) as the transport and pairs with command().

Protocol

The @c9up/comet/protocol surface exposes the spec primitives a server binding needs: parseRequest, isNotification, buildRequest/buildSuccess/buildError, RpcError/toRpcError/isRpcShapedError, and the reserved RpcErrorCode.

parseRequest enforces the envelope MUSTs — the version, the method, an id that is a String/Number/Null, and a params that is a Structured value (§4.2: an Array or an Object, never a scalar). A handler raises a domain error by throwing RpcError; isRpcShapedError also accepts a plain object whose code is a negative integer, the space the spec gives errors, so the numeric code an aborted fetch or a gRPC status happens to carry is not mistaken for one.