How can we use shapefile js in a pipe chain about shapefile

[mbostock]

Seems reasonable. I feel like this would work, too:

export default class ShapefileStream extends Readable {
  constructor(shapeFilePath) {
    super({objectMode: true});
    this.source = shapefile.open(shapeFilePath);
  }
  _read() {
    this.source.then(source => {
      source.read().then(result => {
        this.push(result.done ? null : result.value);
      });
    });
  }
}

[cubodehelio]

I came up with this solution:

// ShapefileStream.js

import { Readable } from 'stream';

const shapefile = require('shapefile'); // undefined when use `import`?

export default class ShapefileStream extends Readable {

  constructor(shapeFilePath) {

    super({objectMode: true});

    this.shapeFilePath = shapeFilePath;
    this.source = null;
  }

  async readStream() {

    if (!this.source) {
      this.source = await shapefile.open(this.shapeFilePath);
    }

    return await this.source.read();
  }

  _read() {

    this.readStream().then((result) => {
      if (result.done) {
        this.push(null);
      } else {
        this.push(result.value);
      }
    })

  }
}

and then..

import ShapefileStream from './ShapefileStream';

const readStream = new ShapeReadStream('./my/shapefile/path.shp');

readStream.pipe(myTransformStream)
   .pipe(myTransformStream2)
   .pipe(myWritableStream);

readStream.on('end', () => {
  console.log('read complete');
})