import type { ChildProcessWithoutNullStreams } from "node:child_process";
import { attachJsonlReader } from "./line-splitter.js";

type Listener = (evt: any) => void;

export class RpcClient {
  private seq = 0;
  private pending = new Map<string, (resp: any) => void>();
  private listeners = new Set<Listener>();

  constructor(private child: ChildProcessWithoutNullStreams) {
    attachJsonlReader(child.stdout, (line) => {
      if (!line) return;
      let msg: any;
      try { msg = JSON.parse(line); } catch { return; }
      if (msg.type === "response" && msg.id && this.pending.has(msg.id)) {
        this.pending.get(msg.id)!(msg);
        this.pending.delete(msg.id);
        return;
      }
      for (const l of this.listeners) l(msg);
    });
  }

  nextId(): string { return `c${++this.seq}`; }

  send(cmd: object): void { this.child.stdin.write(JSON.stringify(cmd) + "\n"); }

  request(cmd: object & { type: string }): Promise<any> {
    const id = this.nextId();
    return new Promise((resolve) => {
      this.pending.set(id, resolve);
      this.send({ ...cmd, id });
    });
  }

  on(_event: "event", cb: Listener): void { this.listeners.add(cb); }
}