Convert Cloud Storage json file to event stream and store output in Firestore

pseudo_code.js

JSONStream = require('JSONStream');
es = require('event-stream');

fileStream = storage.bucket('your-bucket').file('your-JSON-file').createReadStream();
db = admin.firestore();

return new Promise( (resolve, reject) => {
  batchPromises = [];
  batchSize = 0;
  batch = db.batch();
  
  fileStream.pipe(JSONStream.parse(...)
  .pipe(es.map(function (data) {
                  
     // transform the data here
     
  })
  .pipe(menuItem => {
    ref = <get a ref>;
    batch.set( ref, menuItem );
    batchSize++;
    if( batchSize === 500 ) {
      batchPromises.push( batch.commit() );
      batch = db.batch();
      batchSize = 0;
    }
  });
  .on("end", () => {
    if( batchSize > 0 ) { 
      batchPromises.push( batch.commit() );
    }
    Promise.all(batchPromises).then(resolve).catch(reject)
  });
});