node-stream-helpers/test/filestream.test.ts

import * as assert from 'assert'
import { Source } from '../src/Source'
import * as Sink from '../src/Sink'
import * as fs from 'fs'

describe('file stream', function () {
  this.timeout(5000)

  it('should run a stream from a file', async () => {
    const value = await Source.fromReadableBuilder<Buffer>(() => fs.createReadStream('./resources/test/numbers.txt'))
      .map(v => v.toString('utf-8'))
      .statefulMapConcat<string>(() => {
        let current: string = ''
        return [
          v => {
            current = current + v
            if (current.includes('\n')) {
              const splitted = current.split('\n')
              current = splitted.pop()!
              return splitted
            } else {
              return []
            }
          },
          () => current.split('\n'),
        ]
      })
      .map((numbers: string) =>
        numbers
          .split(/\s/)
          .filter(v => v.length > 0)
          .map(v => parseInt(v, 10))
          .reduce((a, b) => a + b, 0),
      )
      .into(Sink.sum)
      .run()

    assert.strictEqual(
      value,
      fs
        .readFileSync('./resources/test/numbers.txt')
        .toString('utf-8')
        .split(/\s/)
        .filter(s => s.length > 0)
        .map(v => parseInt(v))
        .reduce((a, b) => a + b, 0),
    )
  })
})