src/process.ts

// Copyright 2024 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import { ChildProcessWithoutNullStreams } from 'child_process';
// @ts-ignore: no @types/jsonparse available.
import JsonParser from 'jsonparse';

/**
 * A stream of Data coming from a process.
 */
export class DataStreamProcess {
  constructor(
    private process: ChildProcessWithoutNullStreams,
    onData: (data: Buffer) => void,
    onError: (data: Buffer) => void,
  ) {
    this.process.stdout.on('data', onData);
    this.process.stderr.on('data', onError);
  }

  /**
   * A future that resolves when the process exits.
   */
  public get exitCode(): Promise<number | null> {
    return new Promise(resolve => {
      this.process.on('exit', resolve);
    });
  }

  /**
   * Kills the underlying process and all its children.
   */
  public stop() {
    const pid = this.process?.pid;
    if (pid) {
      try {
        // This handles the in-tree use case where `ffx` launches a subprocess `fx ffx`.
        process.kill(-pid);
      } catch {
        // If the process with the given `pid` didn't exist, this error will rise, which we can
        // just swallow.
      }
    }
  }
}

/**
 * A stream of JSON Data coming from a process.
 */
export class JsonStreamProcess {
  private process: DataStreamProcess | undefined;
  private parser: JsonParser;

  constructor(
    process: ChildProcessWithoutNullStreams | undefined,
    private onData: (data: Object) => void,
    onError: (data: Buffer) => void,
  ) {
    this.parser = new JsonParser();
    if (process) {
      this.process = new DataStreamProcess(process, (chunk) => {
        this.parser.write(chunk);
      }, onError);

    }
    let self = this;
    this.parser.onValue = function (value: Object) {
      if (this.stack.length === 0) {
        self.onData(value);
      }
    };
  }

  /**
   * Kills the underlying process and all its children.
   */
  public stop() {
    this.process?.stop();
  }
}