mtui/socat.js

// Simple interface for making a socat process and interacting with it.
// Assumes access to the `socat` command as a child process; if it's not
// present, it will fall back to just writing to the specified file.

import {spawn} from 'node:child_process'
import {writeFile} from 'node:fs/promises'
import EventEmitter from 'node:events'
import path from 'node:path'

import {killProcess, commandExists} from './general-util.js'

export default class Socat extends EventEmitter {
  constructor(path) {
    super()
    this.setPath(path)
  }

  setPath(path) {
    this.stop()
    this.path = path
  }

  async start() {
    this.stop()
    if (await commandExists('socat')) {
      this.subprocess = spawn('socat', ['-', this.path])
      this.subprocess.stdout.on('data', data => this.emit('data', data))
      this.subprocess.on('close', () => {
        this.subprocess = null
      })
      this.subprocess.stdin.on('error', () => {
        this.stop()
      })
    }
  }

  async stop() {
    const proc = this.subprocess
    if (proc) {
      this.subprocess = null
      await killProcess(proc)
    }
  }

  async dispose() {
    // Don't accept any more messages.
    this.disposed = true
    await this.stop()
  }

  async send(message) {
    if (this.disposed) {
      return
    }
    if (!this.subprocess) {
      await this.start()
    }
    if (this.subprocess) {
      try {
        this.subprocess.stdin.write(message + '\r\n')
      } catch (error) {
        // There's no guarantee we'll actually suceed to write - the process
        // or pipe we're writing to could have closed unexpectedly. If that
        // happens, unestablish the socat process; it'll try to reconnect if
        // we send another message.
        this.stop()
      }
    } else {
      try {
        await writeFile(path.resolve(process.cwd(), this.path), message + '\r\n')
      } catch (error) {
        // :shrug: We tried!
        // -- It's possible to get here if the specified path isn't an actual
        // device, which is the case on Linux. Writing to that file (hopefully)
        // works on Windows though, which is the case we're trying to support
        // here. (On Linux you should have socat installed.)
      }
    }
  }
}