mangogrep/index.js

A tool to filter stdin containing a stream of JSON with a CouchDB mango selector

import * as jsonpour from 'jsonpour'
import filter from './filter.js'

// stream stdin --> parser --> filter --> stdout
export async function start(opts) {
  return new Promise((resolve, reject) => {

   if (opts.selector) {
      // just JSON.parse the incoming selector
      try {
        opts.selector = JSON.parse(opts.selector)
      } catch (e) {
        return reject(new Error('invalid selector JSON'))
      }
    } else {
      // if no selector is supplied, select everything
      opts.selector = {}
    }

    // debug
    if (opts.debug) {
      console.error(JSON.stringify(opts.selector))
    }
    
    // stream stdin --> parser --> filter --> stdout
    process.stdin
      .pipe(jsonpour.parse())
      .pipe(filter(opts.selector))
      .on('error', (e) => {
        reject(e)
      })
      .on('finish', () => {
        resolve()
      })
      .pipe(process.stdout)
  })
}